KR20250008770A - Water-activated hydrogel-based medical patches, flexible substrates and methods for making and using such patches - Google Patents

Abstract

A medical patch can include a biocompatible substrate and a dry hydrogel precursor layer on the substrate, wherein the dry hydrogel precursor layer includes an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and a water content of about 2 wt % or less. Both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially non-crosslinked and are mixed with or in direct contact with each other. The medical patch can be formed by coating a molten mixture of the hydrogel precursor in a dry environment, or based on coating a solution of a dry non-aqueous solvent on a porous hydrophilic substrate, such as a compressed gelatin substrate. A flexible medical patch can be formed by a method of compressing the coated substrate, such as calendaring. The medical patch can be used to adhere to a bleeding wound, etc., and can act as a hemostatic patch.

Description

Water-activated hydrogel-based medical patches, flexible substrates and methods for making and using such patches

Cross-reference to related applications

This PCT application claims priority to co-pending U.S. patent application Ser. No. 17/738,847, filed May 6, 2022, to Bassett et al., entitled “Water Activated Hydrogel-Based Medical Patches, and Methods of Making and Using Such Patches,” and Ser. No. 18/142,956, filed May 3, 2023, to Bassett et al., entitled “Water Activated Hydrogel-Based Medical Patches, Flexible Substrates, and Methods of Making and Using Such Patches,” both of which are incorporated herein by reference.

Technical field

The present invention relates to hydrogel-based medical patches, and more particularly to methods of using such patches as hemostatic patches for controlling bleeding, surgical closure, promoting healing, and delivering topical drugs. The present invention also relates to methods of making patches, for example forming a molten mixture that is cast into a suitable substrate. The use of a flexible substrate allows the delivery of folded patches for placement in difficult-to-reach locations.

Hydrogels have a variety of applications in the medical field, including surgical sutures, drug delivery, tissue fillers, and spacers. In the context of wound healing, hydrogel materials can provide a hydrophilic environment that separates tissues and promotes healing. In hemostasis and other wound healing applications, existing products have limitations that limit their effective use.

In a first aspect, the present invention relates to a medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, wherein the dry hydrogel precursor layer comprises an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and a water content of about 2 wt % or less. Typically, both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially non-crosslinked and are mixed with or in direct contact with each other.

In a further aspect, the present invention relates to a medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, wherein the dry hydrogel precursor layer comprises a PEG-electrophilic hydrogel precursor having a plurality of arms having terminal reactive electrophilic groups and a PEG-nucleophilic hydrogel precursor having a plurality of arms having terminal protonated amine groups, and wherein the water content is less than or equal to about 2 wt %. Typically, both the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor are substantially non-crosslinked, and the dry hydrogel precursor layer forms a crosslinked hydrogel within 5 minutes upon hydration with a physiological solution.

In another aspect, the present invention relates to a method for forming a medical patch,

The method comprises the step of applying one or more liquid layers to the porous hydrophilic substrate in a dry atmosphere to form a hydrogel precursor layer on the porous hydrophilic substrate, wherein the hydrogel precursor layer comprises a mixture of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, or a stack of sublayers of each of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with each other. The protected nucleophilic hydrogel precursor comprises an acidified amine, and the liquid comprises the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor. The liquid comprises a melt or a non-aqueous solution of the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor.

In another aspect, the present invention relates to a method of using a medical patch,

The method comprises the step of disposing one or more medical patches on or within a bleeding defect associated with an organ, wherein the medical patch comprises a biocompatible substrate and an initially dried substantially non-crosslinked hydrogel precursor layer on the substrate, wherein the layer comprises an electrophilic hydrogel precursor and a nucleophilic precursor as a mixture or as multiple stacked sublayers in direct contact with one another.

In a further aspect, the present invention relates to a granular composition comprising a mixture of a porous hydrophilic material and a hydrogel precursor, wherein the hydrogel precursor comprises an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and wherein the water content is less than or equal to about 2 wt %. Typically, both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially non-crosslinked and are present in the same granule or separate granules, or a combination thereof. The granular composition can be placed in a bleeding defect where gelation occurs.

In another aspect, the present invention relates to a medical patch comprising a biocompatible substrate and a hydrogel precursor exhibiting a surface along one side of the biocompatible substrate, the hydrogel precursor comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of nucleophilic functional groups, wherein the biocompatible substrate comprises thermally cross-linked gelatin. The hydrogel precursor extends at least partially into the surface of the biocompatible substrate to form a cohesive hydrogel precursor structure. The cohesive hydrogel precursor structure comprises a mixture layer of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor and/or separate adjacent layers, and the medical patch exhibits a shattered surface of the cohesive hydrogel precursor.

In another aspect, the present invention relates to a method of forming a medical patch, the method comprising the steps of: forming a medical patch by compressing a structure comprising a biocompatible substrate and a hydrogel precursor layer or layers coated on the substrate from a melt representing a surface along one side of the biocompatible substrate, wherein the biocompatible substrate comprises expanded gelatin having a disrupted cell structure. The hydrogel precursor layer or layers at least partially extend into the disrupted cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure, wherein upon wetting with a physiological fluid or a physiologically buffered saline solution, the cohesive hydrogel precursor structure crosslinks to form a cohesive hydrogel structure.

In a further aspect, the present invention relates to a method of using a flexible medical patch, the method comprising the step of disposing one or more flexible medical patches on or within a target bleeding site, wherein the flexible medical patch comprises a biocompatible substrate and a hydrogel precursor defining a surface along one side of the biocompatible substrate. The hydrogel precursor comprises an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor as a mixture or in direct contact with each other as multiple stacked regions, wherein the biocompatible substrate has a disrupted cell structure. Typically, the hydrogel precursor is initially dried and substantially non-crosslinked and at least partially expands into the disrupted cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure, wherein the medical patch is hemostatically adhered to the target bleeding site.

In a further aspect, the present invention relates to a method of forming a medical patch, the method comprising the step of applying a liquid hydrogel precursor to a porous hydrophilic substrate in a dry atmosphere, wherein the applying is performed by a print head compressing the substrate at a print location to inject the liquid hydrogel precursor into the compressed substrate. The liquid hydrogel precursor comprises an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, wherein the protected nucleophilic hydrogel precursor comprises an acidified amine, and the liquid hydrogel precursor comprises a melt or non-aqueous solution of the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor.

In a further aspect, the present invention relates to a medical patch comprising a biocompatible substrate and a hydrogel precursor, wherein the hydrogel precursor comprises a solid mixture and/or separate solid layers of an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of nucleophilic functional groups, wherein neither the electrophilic hydrogel precursor nor the nucleophilic hydrogel precursor are substantially crosslinked. The biocompatible substrate comprises thermally crosslinked gelatin having a disrupted cell structure, wherein the hydrogel precursor at least partially extends into the disrupted cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure.

Figure 1a is a perspective view of the hemostatic patch structure.
Figure 1b is a perspective view of a multilayer hemostatic patch structure.
Figure 1c is a perspective view of a hemostatic patch structure having a compressed substrate.
Figure 1d is a perspective view of a hemostatic patch structure having a cohesive hydrogel precursor network with a compressed substrate and a broken surface.
Figure 2 is a perspective view of a device for making a hemostatic patch by spray-coating a mixed precursor composition onto a substrate.
FIG. 3a is a side view of a device for making a hemostatic patch by slot die coating a mixed precursor composition onto a substrate.
FIG. 3b is a side view of a slot die coating device similar to the device of FIG. 3a for adjusting the coating head to press the substrate during coating.
FIG. 4a is a side view of a device for making a hemostatic patch by continuously roll slot die coating a mixed precursor composition onto a substrate.
FIG. 4b is a flow chart for a two-step compression process according to an embodiment of the present invention.
Figure 4c is a side view of a process flow for making a flexible hemostatic patch product from a gelatin sheet and a hydrogel precursor composition.
Figure 4d is a side view of the gap between the calendar rollers.
Figure 5 is a diagram of a hemostatic patch wrapped around a tubular organ.
Figure 6 is a drawing of a hemostatic patch attached to a non-vascular organ.
Figure 7 is a drawing of a hemostatic patch attached to the skin.
Figure 8a is a cross-sectional view of a bleeding defect in the tissue.
Figure 8b is a cross-sectional view of a hemostatic patch after placement on the bleeding defect of Figure 8a.
Figure 8c is a cross-sectional view of the hemostatic patch of Figure 8b attached to a bleeding defect.
Figure 8d is a cross-sectional view of healed tissue after the hemostatic patch has been absorbed.
Figure 9 is a diagram of the Adam's Scale for defect bleeding scores.
Figure 10a is a photograph of the initial placement of the patch within the channel defect.
Figure 10b is a photograph taken 1 minute after the arrangement shown in Figure 10a.
Figure 11 is a force versus time plot for a representative patch sample evaluated using a commercial texture analyzer.
Figure 12a is a drawing showing a conical hemostatic patch placed within the cervix using a conical mandrel.
Figure 12b is a drawing of a conical hemostatic patch placed on the cervix, the left illustration showing the conical mandrel pressing the patch into the cervix, and the right illustration showing the conical mandrel removed and the conical patch remaining on the cervix. Only the conical end of the mandrel is depicted in the left illustration, and the handle of the conical mandrel is not depicted.
Figure 13a is a perspective view of a flexible hemostatic patch folded in an accordion shape.
Figure 13b is a drawing showing insertion of a flexible hemostatic patch folded in an accordion shape into a cannula using forceps.
Figure 13c is a drawing showing a flexible hemostatic patch folded widthwise in an accordion shape.
Figure 13d is a drawing showing insertion of a flexible hemostatic patch folded in an accordion shape into a cannula using forceps.
Figure 14 is a drawing showing the insertion of a flexible hemostatic patch folded in an accordion shape into a laparoscopic surgical site using forceps.
Figure 15a is a SEM image of the cross-linked gelatin substrate.
Figure 15b is a SEM image of the cross-linked gelatin substrate of Figure 15a after calendaring.
Figure 15c is a SEM image of the cross-linked gelatin substrate.
Figure 15d is a SEM image of the cross-linked gelatin substrate of Figure 15c after calendaring.
Figure 16a is a SEM image of the surface of the precursor-coated gelatin substrate.
Figure 16b is a SEM image of the surface of the precursor-coated gelatin substrate after compression with a calendar roller set at a spacing of 5 mm.
Figure 16c is a SEM image of the surface of the precursor-coated gelatin substrate after compression with a calendar roller set at a spacing of 2 mm.
Figure 16d is an SEM image of the surface of the precursor-coated gelatin substrate after the first compression with the calendar roller gap set to 5 mm and the second compression with the calendar roller gap set to 2 mm.
Figure 17a is a SEM image of a cross-section of a precursor-coated gelatin substrate.
Figure 17b is a SEM image of a cross-section of the precursor-coated gelatin substrate of Figure 17a after calendaring.
Figure 18a is a first photograph of a precursor coating substrate without compression before coating.
Figure 18b is a second photograph of a precursor-coated substrate without compression before coating.
Figure 18c is a photograph of a precursor-coated substrate that was calendered before coating.
Figure 19 is a plot showing the average fluid absorption rate over time for uncompressed and compressed substrates.

Medical patches are formed by forming a dried hydrogel precursor layer on a substrate as a mixture or by directly contacting adjacent sublayers, which, when hydrated with a biological fluid, spontaneously crosslink to form a hydrogel that can adhere to tissue. Typically, the hydrogel precursor need not react with blood or tissue, since any physiological fluid can react with equal or nearly equal amounts of nucleophilic and electrophilic functional groups to activate crosslinking. The processing to form the hydrogel precursor layer is typically selected to protect the nucleophilic groups and avoid moisture even if the reactive species come into contact, thereby avoiding actual crosslinking during processing. The processing can include forming a dehydrated molten mixture of the precursor and then coating or casting to form a layer, or coating a non-aqueous solution of the mixture and removing the solvent. The substrate supporting the dried hydrogel can be selected to be absorbent, so that the substrate can further aid in the hemostatic function of the patch. Furthermore, the processing of the patch and the deposition of the hydrogel precursor material can be designed to obtain a flexible patch with good cohesion of the hydrogel precursor material that adheres well to the substrate and provides a surface for adhesion to the wound within the finished patch. The use of a flexible biodegradable substrate allows the patch to be placed in inaccessible locations and/or in wounds of unusual shapes. Contact with tissue during the crosslinking process can promote the formation of the desired adhesive bond, whether or not covalent bonding occurs with the tissue, and whether or not blood is present. The patch with the selected components can be folded without fragmentation, so that it can be folded for insertion into the wound rather than for delivery or insertion over the wound during laparoscopic surgery via a trocar. The appropriate choice of substrate increases the flexibility of the patch, and the preferred patch can be composed of a precursor layer appropriately incorporated into a compressed gelatin sponge that penetrates the compressed sponge. The hydrogel precursor layer adheres remarkably well to the surface, providing bonding along the edges of the patch without the need for direct contact with blood or the wound. The results found in these patches indicate that the material is also quite useful as a filler for wounds, etc., which may be formed into a finely chopped patch or an equally formed material, wherein the components may be individually chopped, crushed or otherwise fragmented.

The gelatin substrate can provide desirable fluid absorption as well as biodegradation within a reasonable time frame. Foamed gelatin in particular satisfies these properties, but other porous gelatin forms, such as fused fiber gelatin, can also have similar properties. However, it has been found that a higher level of flexibility is required than can be obtained directly from these materials. Compressing the substrate, such as by calendering, prior to and/or after deposition of the precursor material, may be desirable to impart a significantly higher level of flexibility. In the context of using a porous gelatin substrate, the precursor material is coated onto the substrate surface as a mixture of precursors and/or as separate precursors, thereby providing a mixture layer and/or separate adjacent layers of electrophilic hydrogel precursor and nucleophilic hydrogel precursor. The coating substrate should be flexible yet mechanically robust in terms of cohesion of the mixture layer and/or separate adjacent layers and adhesion to the substrate, and should not delaminate or peel off the precursor in dry patches. It was found that when a hydrogel precursor in a molten or non-aqueous solution is injected into a substrate under slight compression, the adhesion of the hydrogel precursor to the porous substrate is improved and the cohesion of the hydrogel precursor is also well maintained. Due to the elasticity of the substrate, the thickness of the substrate can be restored after the hydrogel precursor is deposited, but when the hydrogel precursor is well penetrated and deposited into the substrate, the hydrogel precursor is well adhered to the substrate and at the same time, most or all of the surface of the hydrogel precursor is exposed, so that the patch is attached to the tissue surface during use. After the hydrogel precursor is deposited, the structure can be compressed by calendering or the like to further improve the flexibility of the patch, which can cause the surface of the precursor to break. As a result, the patch structure can have the desired flexibility while maintaining the good cohesion and adhesion of the hydrogel precursor, so that peeling or delamination of the hydrogel precursor can be avoided. Although the hydrogel precursor has some of the characteristics of a surface layer, the hydrogel precursor also has some of the characteristics of an integrated structure by at least partially penetrating the substrate. The cohesive hydrogel precursor structure can be attached to the substrate via a diffusion boundary between the hydrogel precursor and the substrate. The gelatin hairs of the substrate can penetrate into the hydrogel precursor that appears along the surface of the substrate, because the substrate surface is not microscopically smooth, and the hydrogel precursor can penetrate and become embedded into a portion of the substrate, forming a diffusion boundary between the hydrogel precursor and the substrate within the cohesive hydrogel precursor structure. In various contexts, the hydrogel precursor can alternatively be described as a layer or coating that represents the surface of the hydrogel precursor, or as a cohesive hydrogel precursor structure (or cohesive hydrogel precursor network). Even if there is no clear boundary between the substrate and the hydrogel precursor, the hydrogel precursor still presents a surface along the substrate, allowing the patch to adhere to wet tissue as the hydrogel precursor hydrates.

The dry layer of the hydrogel precursor, such as a mixture, typically comprises a first hydrogel precursor having a plurality of electrophilic functional groups and a second hydrogel precursor having a plurality of protonated amine groups, typically primary amines. In particular, the nucleophilic amine can be protonated to form a cationic ammonium group, which protects the amine from nucleophilic reactions until the amine is deprotonated. A halide, such as chloride, or the conjugated anion of another strong acid can serve as the counter ion. The electrophilic and nucleophilic functional groups can react to form covalent crosslinks when the mixture is hydrated and the acid is diluted during hydration to deprotonate the ammonium groups. Thus, in the patch product, the hydrogel precursor is substantially non-crosslinked, as described in detail below. In some embodiments, the patch or portions thereof can be degraded. The precursors can be applied as separate layers or as a premixed melt. If a melt is chosen, it is advantageous to use the melting point of the mixed precursors to maintain a solid at room temperature to provide maximum storage stability. The precursor mixture may contain components that are liquid at room temperature, but the melting point of the mixture is higher than room temperature. In principle, the precursor mixture may be a viscous liquid at room temperature, but the resulting patch may require refrigeration to ensure storage stability. The patch may be used as an implant or to heal exposed tissue or skin tissue. The substrate may be selected accordingly. The patch may be effective in stopping bleeding. For hemostatic applications, an absorbent substrate is highly desirable. The absorbent substrate may be formed of a combination of a natural material such as collagen, gelatin, cellulose or other similar biopolymers, or a synthetic hydrogel such as a polymer including polyethylene glycol, polyvinyl alcohol or other water-soluble or water-swellable synthetic polymers, or a biopolymer. Substrates that are flexible and drape well generally provide desirable patching characteristics, or those that quickly soften and drape when exposed to moisture may also provide desirable characteristics for a variety of applications.

In some embodiments, no buffer was added to the precursor layer, but the results clearly demonstrate that rapid and good gelation occurs even without a buffer. An appropriately selected buffer may be present without interfering with the function of the precursor layer. In this case, an inorganic buffer may be desirable as it may remain separate until activated by physiological fluids. Carbon dioxide in the air or in the laparoscopic environment dissolves in water to form carbonic acid, which may provide a low buffering capacity. Carbonic acid evaporates as carbonic acid rather than condenses as water is removed. An improperly selected buffer may be undesirable as it may cause undesirable premature crosslinking of the precursor prior to use or may slow crosslinking after application to the tissue. Even if water is removed from the patch during processing, trace amounts of water may still cause some degree of crosslinking if a higher pH buffer is present, and more acidic buffers may slow crosslinking when in contact with physiological solutions that generally have a slightly basic pH. However, experience with these polymer systems generally suggests that the use of phosphate buffers and other neutral to slightly acidic buffers can moderately slow down gelation. There is evidence that patches without buffer can also provide desirable performance with adequate storage stability. Patches without significant amounts of buffer added or patches with acceptable levels of buffer are more easily described in terms of patch functionality such as storage stability and gelation rate, as will be discussed in more detail below. When a buffer is included, for example, the buffer may be applied to the substrate in powder form and the hydrogel precursor layer placed thereon, or, if compatible with the non-aqueous form of the precursor layer, mixed into the hydrogel precursor layer.

Various suitable substrates are described below. In particular, gelatin-based sponge patches have been found to have excellent patching effects. When such sponges are used as substrates and compressed to destroy the cell structure of the sponge, better flexibility can be obtained. Although the mechanical strength of the substrate decreases due to the compression of the gelatin cell structure, the substrate correspondingly becomes significantly more flexible, while maintaining sufficient mechanical stability for applying a hydrogel precursor layer to the substrate and applying the patch. Various processing protocols can be effectively utilized, but particularly desirable results can be obtained by a two-step compression process. The hydrogel precursor layer can be added after the first compression and before the subsequent compression. The hydrogel precursor penetrates into the destroyed cell structure of the sponge to stabilize the patch, and the hydrogel precursor layer is destroyed during the additional compression, which not only improves the flexibility of the coating substrate, but also promotes and accelerates the hydration of the precursor layer, thereby accelerating the adhesion effect.

As described in more detail below and clearly exemplified, the patch adheres very well to wet tissue. An effective manufacturing method is described. The hydrogel is designed so that the electrophilic and nucleophilic functional groups are present in approximately equal amounts, so that complete crosslinking can occur between the hydrogel precursor and the precursor, and it is expected that crosslinking will occur without necessarily bonding the functional groups of blood or tissue. The strong adhesion of the patch to blood or tissue without covalent bonding is a surprising result based on the knowledge in the art. This improved design provides excellent performance such as strong adhesion, rapid gelation, etc. while maintaining excellent shelf life. If the gelation time is to be shortened, the gelation process can be further accelerated by applying a buffer/accelerator solution, such as through the backing, immediately after applying the patch to the tissue. In principle, the buffer/accelerator solution can be added immediately before applying the patch to the tissue, but this method may result in too rapid gelation and poor adhesion.

Patches are particularly suited to stop active leaks or bleeding. Such seals are not possible with liquid precursors, which are typically provided only as spray-on sealants, because the precursors are displaced as the active fluid escapes. In the case of patch-based sealants, which are the subject of the present invention, manual pressure applied as part of the patch application can temporarily control the outflow of active fluid and allow the sealant to become activated and adhere to the tissue surface, thereby forming an effective seal.

For some wounds, such as punctured but not bleeding wounds, insertion of chopped patch material may be effective in stabilizing the wound by cross-linking the material. The healthcare provider may shred the patch directly or may distribute the chopped patch material as is. To create a chopped patch configuration, it is not necessary to completely form a patch to produce a similar material. A substrate, such as a gelatinous substrate, may be chopped, and a precursor mixture may be formed and milled/reduced into particulates. For example, a molten mixture or solution may be spray dried/cooled to directly form a particulate material, which may then be further milled or sieved, if desired. Separately chopped/milled materials may be mixed and distributed and used. While forming a mixture of precursors for milling may be desirable for rapid gelation/cross-linking, individual powders of the precursors may alternatively be mixed. For these implementations, the relative amounts of the components may follow the ranges described for the patch, although slightly different amounts may be selected for commercialization based on clinical experience.

A granular composition comprising a mixture of a porous hydrophilic material and a hydrogel precursor can be prepared from a finely chopped patch, wherein the porous hydrophilic material is the substrate of the patch and the hydrogel precursor is the dried layer of the hydrogel precursor on the substrate. The mixture can be homogeneous or non-homogeneous. In some embodiments, the granular composition is a mixture in which the porous hydrophilic material is supplied separately from the hydrogel precursor. For example, the porous hydrophilic material can be a finely chopped uncoated substrate or a porous hydrophilic material provided in particulate form, such as gelatin microparticles or gelatin powder. In some embodiments, the porous hydrophilic material can be a foam, a nonwoven tufting material, or a nonwoven felting material. Two or more porous hydrophilic materials can be used together. Examples of separate hydrophilic porous materials include, for example, substrates made of the same material but having different porosities, pore sizes, and/or particle sizes, or substrates having different compositions. The hydrogel precursors can be provided as a mixture of electrophilic hydrogel precursor and nucleophilic hydrogel precursor within the same granule, can be provided as separate granules of electrophilic hydrogel precursor and separate granules of nucleophilic hydrogel precursor, or can be provided as combinations thereof. In some embodiments, the weight ratio of the chopped substrate/porous hydrophilic material in the chopped patch composition can be from about 5 wt % to about 75 wt %, in some embodiments from about 7 wt % to about 50 wt %, and in further embodiments from about 10 wt % to about 35 wt %. In other embodiments, the weight ratio of the chopped substrate can be less than 25%, less than 10%. In another embodiment, the granular composition of the precursor can be used without the chopped substrate, and the weight percentage of the chopped patches is 0 wt%. A person skilled in the art will recognize that additional ranges of compositions of porous hydrophilic materials within the stated ranges are contemplated and are within the scope of the present invention.

The granular composition can have granules comprising any combination of the porous hydrophilic material and the hydrogel precursor. Granules of different compositions can have different average granule diameters. In one embodiment, the porous hydrophilic material and the hydrogel precursor form a complex within the granule. In another embodiment, the porous hydrophilic material and the electrophilic hydrogel precursor form a complex within the granule, and the nucleophilic hydrogel precursor is present as a separate/distinct granule. In another embodiment, the porous hydrophilic material and the nucleophilic hydrogel precursor form a complex within the granule, and the electrophilic hydrogel precursor is present as a separate/distinct granule. In another embodiment, the porous hydrophilic material is present in granule form, and the complex of the hydrogel precursor is present as a separate/distinct granule. In another embodiment, the porous hydrophilic material, the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are present as separate/distinct granules. The granule composition can be provided as granules of the porous hydrophilic material coated or at least partially coated with one or both of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor. The coating of the precursor or precursors can be accomplished by spraying a melt or solution of the precursor or precursors. Multiple layers of coating can be applied, for example, one precursor layer over another.

The granular composition may have a variety of granule shapes, from powders to small particles, coarse pieces such as those obtained by chopping a substrate or patch. The small particles may have an average diameter of about 0.001 mm to about 5 mm or about 0.01 mm to about 3.5 mm. The granules may or may not be approximately spherical and may be of any reasonable shape. The granular composition may further comprise a visualizing agent and/or a therapeutic agent as described for the patch. The granular composition may be placed on or within the bleeding defect, and optionally pressure may be applied. The bleeding defect may be partially or completely filled or thinly coated with the granular composition. Those skilled in the art will recognize that additional ranges of average diameters within the above stated ranges are contemplated and are within the scope of the present invention. When the patch is chopping for use by a healthcare professional, the resulting patch pieces may generally vary considerably in size and shape, depending on the needs of the healthcare professional.

Due to the ability to have well-mixed precursors, rapid gel formation is possible even if the amine is initially protected. Crosslinking begins as soon as the acid-protected group is diluted with a physiological solution and neutralized. Physiological solutions are generally slightly alkaline, for example blood plasma, which has a physiological pH of 7.32 to 7.42 pH units. In the case of the PEG-NH ₂ group, the -NH ₃ ⁺ moiety must be deprotonated even at neutral water pH values to form the nucleophilic active form. Thus, when properly hydrated, the patch can gel in less than a minute, and rapid gelation has been demonstrated in the examples. Due to the chemistries used, the patch will generally adhere to any moist tissue surface with a physiological solution, and direct blood and/or wound contact is not required, but may be present. The patch is designed for rapid and predictable efficacy and can be of great help in performing efficient medical procedures.

Each of the precursor compositions can be selected to form a heat-flowable composition that can be mixed as a liquid without decomposition. The heat-flowable composition or the mixture of two or more heat-flowable compositions can be a pure melt or a pure melt mixture, respectively, where "pure" refers to a liquid composition without the addition of a solvent. The melt mixture can then be coated on a substrate and cooled to form a patch. In particular, precursors having a polyethylene glycol core generally form a liquid that can flow at relatively low temperatures. The coated substrate can be formed using slot coating, extrusion, screen printing, or other suitable coating processes. In some embodiments, the precursor can be dissolved in some organic solvent in which the precursor is suitably stable, for example, an aprotic polar solvent. The mixed precursor solution can be coated on a substrate (e.g., spray coated) and then dried to remove the solvent. In an alternative embodiment, the precursor can be treated using a non-aqueous solvent solution, the solvent being selected to prevent deprotonation of the acidified amine groups. The precursor solution can be deposited using techniques similar to those for dissolving the precursor.

Medical patches can be used for a variety of purposes, such as closing a patient's wound as part of a procedure, or applying it along the skin for wound healing or surgical closure, and can be of considerable value. The patches of the present invention offer the significant advantage of activation by any physiological fluid, since contact with blood or tissue is not explicitly required. Thus, even if a portion of the patch is in direct contact with blood or tissue, the entire patch can form an effective seal, including the edges that are not in direct contact with blood or tissue. For example, the absorbent substrate can absorb the physiological fluid, and the wet portion of the patch with the physiological fluid can also absorb it over the entire surface of the patch. And since no portion of the patch is required to be in direct contact with blood or tissue, provided there is adequate moisture, for example, lymph fluid can be drawn or transferred directly from the substrate to effectively activate the patch. The patches can be used for human or veterinary purposes. The prepared patches may not contain blood or human components.

The patch can generally have a substrate layer, and a hydrogel precursor layer over the substrate layer, wherein the precursor layer can be a mixture of precursors and/or sublayers of the same or different compositions. The substrate layer can be homogeneous, or can be composed of multiple layers and/or structured layers. Typically, the substrate layer is dry when the patch is formed and is formed of a biodegradable material, although in certain applications it may be desirable to use a non-degradable substrate. The substrate is very liquid-absorbent, which can help manage blood and other body fluids while the hydrogel closes the wound. The patch is generally thick enough to provide the desired mechanical integrity, but not too thick, and a patch of appropriate thickness can provide the desired crosslinking and hydration in an appropriate amount of time while also being able to degrade in an appropriate amount of time and without being too bulky.

The precursors can be selected so that they form a fluid state when heated at an appropriate temperature. In embodiments where the precursors are mixed in a fluid state during processing, the formation of the molten mixture must be thermally stable for each precursor. Processing can be performed in a low humidity environment so that the hygroscopic material does not absorb undesirable moisture from the air. In general, the flow characteristics of the heated precursor composition are greatly influenced by the polymer core to which the functional groups are suspended. In particular, polyethylene glycol-based precursors have the advantage of relatively low flow temperatures and are suitable for approved implantable medical devices, although other hydrophilic precursor cores can be used.

In some embodiments, if the precursor is soluble in a suitable organic solvent that does not induce crosslinking, the precursor may be mixed into an organic solution. Various solution coating techniques may be suitable for forming the precursor coating with the solution mixture. After the coating is formed, the organic solvent may be evaporated and removed, thereby forming a dry coating. After drying, the patch may be packaged in a waterproof pouch or the like, similar to a cooled melt-formed patch.

To obtain the desired shelf life, proper handling and processing characteristics and to set upon application, the amine precursors are provided in the form of acid salts/conjugates, or the mixed precursors may be free of buffers or may contain only appropriately selected buffers that do not unduly slow gelation or make the patch unstable for storage. The presence of alkaline pH buffers may result in the deprotonation of the amine during processing, thereby amplifying the instability of the crosslinks. Since all hydrophilic components are present during synthesis, water is deprotonated, but it is not possible to obtain extremely low levels of water. On the other hand, the amines are selected to be readily deprotonated upon contact with physiological fluids, and therefore do not require buffers to achieve rapid gelation.

Other hemostatic hydrogel patches are also known. For example, fibrin-based patches are commercially available. TACHOSIL® is a fibrin-based patch from Baxter. Similar powders and syringe-delivered matrices based on fibrin or other blood-based components are also available. Another approach to the patch is to partially crosslink the hydrogel within the patch, leaving unreacted electrophilic groups. Partial crosslinking provides a solution process for creating the hydrogel precursor layer of the patch, which is intentionally functionalized (lacking nucleophiles) and resulting in a significant number of unreacted electrophilic groups. The unreacted electrophilic groups are intended to react with nucleophilic groups in the blood or tissue at the wound site, such as naturally occurring amines. This approach has the disadvantage that the patch may partially adhere and/or have poor patch adhesion, as well as at the edges of the patch where the patch does not directly interact with the wound and only adheres to tissue or blood, and where there is no direct contact with blood or tissue. Hydrogels based on this approach have been described using polyoxazoline copolymers as the core of the functionalized precursor. See published U.S. patent application Ser. No. 6,518,411 entitled "Cross-Linked Polymers and Implants Derived From Electrophilically Activated Polyoxazoline", which is incorporated herein by reference. These polyoxazoline-based cross-linked polymers are described as adhesives and not specifically described as hydrogels. In contrast, the hydrogels described herein have all or essentially all cross-linking occurring after application and rely on reaction with patient-supplied tissue or blood or other nucleophiles for cross-linking, although some reaction between the precursors of the invention and blood or tissue may occur. The hydrogel precursors of the present patches react virtually exclusively with themselves, yet exhibit excellent adhesion.

A polyethylene glycol-based (PEG-based) hemostatic patch is sold under the trade name Veriset™ (Medtronic). Veriset™ is believed to incorporate the technology described in published U.S. patent application Ser. No. 2010/0100123A to Bennett ('123 application), entitled "Hemostatic Implant", which is incorporated herein by reference. Such patches include separate precursor components. In contrast, the present approach includes mixed or intimately contacted hydrogel precursor components that can rapidly form a highly crosslinked, homogeneous hydrogel upon contact with a patient. As a result of the mixing or intimate contact of the non-crosslinked precursors, the hydrogel can rapidly gel to form a homogeneous hydrogel with good mechanical stability, good adhesion, and predictable properties. Another hemostatic patch is sold by Baxter International, Inc. (IL, USA) under the name HEMOPATCH™ with a PEG-based NHS hydrogel precursor. HEMOPATCH's precursor coating is intended to cross-link with amines in tissues and blood.

In general, the patches of the present invention comprise a substrate and a hydrogel precursor layer. After placement at a tissue site, crosslinking of the hydrogel precursor layer helps to adhere the patch to the site. The substrate is generally adhered to the precursor layer and may serve to facilitate hydration and stabilization of the patch, particularly when used in hemostatic situations. For this purpose, the substrate is typically highly absorbent and porous while maintaining mechanical integrity. In this manner, the substrate is able to absorb body fluids, such as blood, to stabilize the patch site and hydrate the hydrogel to facilitate crosslinking, but is not so porous that blood passing through the substrate would adhere to the substrate surface, such as gauze or a surgeon's glove. Substrate absorption can be assessed based on swelling, and the substrate can form a hydrogel that does not exhibit additional crosslinking upon hydration. The porosity of the substrate generally allows some penetration of the hydrogel precursor into adjacent substrate surfaces.

In the hydrogel precursor layer of the patch of the present invention, the two precursors for crosslinking can be mixed in a dehydrated state or formed as a sublayer within the precursor layer. The amine groups are in a protonated acidic state. The precursor layer may substantially require no buffer to support relatively rapid crosslinking upon hydration by physiological fluids. The precursor layer is stable under dry storage for a period suitable for distribution of the product having a commercially suitable shelf life. Of course, the precursors may contain trace amounts of anionic contaminants, but suitably pure precursors should eliminate concerns about quality. One or more amine-terminated precursors can be used to form the patches described herein, and one or more precursors that react with nucleophilic terminal groups can also be used.

The crosslinking reaction involves the addition reaction of a nucleophilic amine with an appropriate group. The addition reaction generally proceeds at an appropriate rate at high pH values, typically above pH 7. Without the use of an activating solution, deprotonation of the amine can occur relatively quickly upon hydration with a physiological solution, allowing the crosslinking reaction to occur in a short time (e.g., <3 minutes). The results in the examples confirm rapid gelation. Since the precursors are mixed or in close contact in the dry patch, the reactive crosslinking groups can be in close proximity without significant movement of the macromolecular precursor molecules involved in the crosslinking. As described and exemplified below, the initially uncrosslinked precursor can rapidly gel, leading to adhesion of the patch. In general, it is not necessary to use a high pH buffer to induce gelation at an appropriate rate, and a high pH buffer, such as a borate buffer, can help to shorten the storage time. A low pH buffer, such as a phosphate-based buffer, generally increases gelation time, but when used in appropriate amounts, it may not slow down the gelation rate unacceptably. Low pH buffers may not adversely affect shelf life. If desired, additional external high pH buffer may be administered to the patient after application of the patch to shorten the reaction time, but this is not required.

The substrate supporting the hydrogel precursor may be absorbent, which may provide several advantages. First, it may absorb body fluids such as blood, lymph, etc., which may aid the healthcare professional in managing the wound while the patch is being applied. Additionally, absorption of physiological fluids by the absorbent substrate may aid in hydration of the hydrogel precursor. Thus, the use of an absorbent substrate may shorten the gelation time, which may be as short as less than a minute. The substrate is generally biodegradable, but in some embodiments, the substrate may not degrade over the relevant time scale, including for example, some applications, including external application of the patch. When considering external use of the patch, the backing substrate may not be biodegradable, and the patch may be removed once healing is complete, or the hydrogel formed by the precursor in contact with the tissue may be absorbed, releasing the patch substrate after several days. In certain cases, it may be advantageous to deliver the hydrogel itself, in which case a nonporous backing substrate may be used to release the hydrogel into the wet tissue without adhering to the hydrogel itself. In these applications, substrates made from polymeric substrates that have low adhesion to the hydrogel precursor, such as polytetrafluoroethylene, polyethylene, polyurethane, etc., may be useful. The release layer for an adhesive bandage may be tailored for this application.

For most hemostatic applications using patches, it is desirable that the substrate be biodegradable to non-toxic degradation products that can be removed from the patient within a reasonable period of time. The substrate should be capable of absorbing body fluids and of interfacing with the permeable precursor layer. While a variety of natural and man-made materials, usually polymers, can provide this functionality, gelatin sponge materials have been shown to perform particularly well in patch structures. To achieve the desired level of flexibility, the gelatin sponge can be compressed to disrupt the gelatin cell structure, and the precursor layer can penetrate into the disrupted cell structure to form an integral, stable structure with desirable absorption properties.

Gelatin is a hydrolyzed product of collagen, a major component of the extracellular matrix of animals. Collagen is usually harvested from various livestock. Collagen is an insoluble fibrous protein in its original state. Hydrolysis breaks down the protein polymer strands into smaller units, resulting in gelatin that can be processed. The exact properties of gelatin can vary depending on the processing method. However, gelatin is generally soluble in hot water and other polar solvents. To make gelatin insoluble, gelatin can be cross-linked to adjust certain properties. Sufficient cross-linking can be achieved using heat to avoid the use of toxic chemicals in the cross-linking. To form an absorbent substrate, gelatin is formed into a sponge with a cell-type structure. Foamed gelatin cell structures can be formed without cross-linking.

The formation of gelatin sponges is known and is then typically stabilized by chemical crosslinking. See, for example, published U.S. patent application Ser. No. 2007/0077274 to Ahlers entitled "Method for Producing Shaped Bodies Based on Crosslinked Gelatin" (the '274 application), which is incorporated herein by reference. The '274 patent relates to existing crosslinked gelatin products that lack the durability required for certain applications. The crosslinked gelatin is formed using a pore-forming agent, such as air, to provide pores in the sponge structure. The product of the '274 patent is still biodegradable. Gelatin sponges are commercially available as hemostatic agents. For example, gelatin sponges are available from Gelita AG (Germany, assignee of the '274 patent) and Ethicon (USA). Non-crosslinked gelatin sponges can be obtained. Gelita and Ethicon market gelatin sponges as hemostatic patches, Surgi-Foam® (Ethicon) and Gelita-Spon® (Gelita).

While chemical cross-linking may be desirable for longer durability, chemical cross-linking may involve the use of toxic chemicals or other moieties that are undesirable for the biodegradation of the material, which may result in the material being too durable. Chemical cross-linking may also alter the mechanical properties of the substrate, making it more brittle. On the other hand, gelatin that is not fully cross-linked may degrade too quickly before it can achieve hemostasis, thereby losing its ability to absorb body fluids. Thermal cross-linking can achieve the desired balance of properties without introducing chemicals that may complicate biocompatibility. As noted in the '274 patent, thermal cross-linking of gelatin causes dehydration, which may form cross-links. Thermal cross-linking is discussed in more detail below.

Previous studies have suggested that compressing gelatin sponges can increase their flexibility. The '274 application discusses "mechanical acting" including passing the crosslinked gelatin sponge through rollers to increase its flexibility. They suggest a 2-10x increase in density, but do not describe the mechanical properties of the material as a result of the mechanical acting, and the reference suggests that dissolution over time is not affected, without providing data. The use of compressed gelatin substrates in conjunction with hydrogel precursors is described in published U.S. Patent Application No. 2021/0213157 to DeAnglis et al., entitled "Flexible Gelatin Sealant Dressing With Reactive Components" (the '157 application), which is incorporated herein by reference. The '157 application refers to compressing the gelatin after crosslinking. Accordingly, although the '157 application states that compressed gelatin sponges have greater strength due to the amine groups of the proteins being physically closer together, resulting in a higher crosslinking density, the '157 application suggests that crosslinking is optional. The '157 application does not appear to suggest the possibility of thermal crosslinking.

The '157 application references previously published U.S. patent applications teaching combinations of hydrogel precursors with absorbable substrates, see Bennett et al., No. 2011/0045047, entitled "Hemostatic Implant", which is incorporated herein by reference and appears to be a follow-on to the above-cited '123 application. The '157 application points out undesirable aspects of the prior work and presents an alternative using a dry precursor powder deposited on a porous substrate.

The '157 application exemplifies the use of commercially available substrate materials, specifically SURGIFOAM® product codes 1974 and 1975 and SPONGOSTAN® gelatin films, which are claimed to be compressed. The '157 application does not describe the detailed properties of these substrates, nor any specific further processing performed prior to application of the hydrogel precursor. As noted above, the precursor is added in the form of a finely dried powder comprising a mixture of 4-arm PEG-SG (succinimidyl glutarate) (MW=4000 Da), 4-arm PEG-amine (MW=3,000 Da), and sodium bicarbonate powder. The powder is suspended in an organic solvent, applied, and then evaporated. Powder precursors lack the advantages of the solid precursor layers described herein.

Commercially available hemostatic gelatin sponges are typically chemically cross-linked, for example using aldehydes such as formaldehyde or glutaraldehyde, which are thought to stabilize the structure for an appropriate duration of time when in contact with biological fluids. As noted above, the '157 application uses a commercial substrate from Ethicon, Inc., and provides no details on the manufacture or specific properties of the substrate other than dimensions. As described herein, processing involves a coating process that forms a successive layer of a precursor that is designed to be stable and non-cross-linked until activated by a fluid or water. The precursor layer then acts synergistically with the substrate, such that the precursor layer stabilizes the substrate and the hydrogel precursor penetrates the substrate, thereby stabilizing the hydrogel precursor from delamination or peeling.

In the applicant's processing, the patch structure is compressed after the hydrogel precursor layer is applied. This compression step generally destroys or breaks the formed precursor layer, forming micro-breaks and/or cracks throughout the surface. The micro-breaks and/or cracks occur as the flexibility of the formed patch increases. The hydrated patch adheres to the tissue, whether or not it is in direct contact with the wound along a portion of the patch. The gelatin sponge may contain additives such as plasticizers and possibly other agents, and it is thought that the mechanical properties of the patch will be improved more if the patch material is not too elastic, so that the thickness reduction upon compression is greater and the phenomenon of bulging after compression is less. Then, the cell structure of the gelatin sponge is destroyed, which can further promote hydration and improve flexibility. In addition to compressing after the precursor layer is placed, the gelatin patch may also be compressed before the precursor layer is applied. The initial compression can facilitate the penetration of the precursor layer into the gelatin while maintaining the surface of the precursor layer.

To enhance the adhesion of the hydrogel precursor to the porous gelatin substrate, it has been discovered that the hydrogel precursor can be deposited onto the substrate under light compression. The print head can be adjusted to provide the desired deposition configuration. Since the porous gelatin substrate may be somewhat elastic, moderate compression of the hydrogel precursor layer may not result in a sustained change in substrate thickness. Nevertheless, deposition onto the substrate under compression appears to allow greater penetration of the hydrogel precursor into the substrate. The resulting patch structure exhibits the desired degree of hydrogel precursor adhesion and cohesion, thereby reducing or eliminating the phenomenon of hydrogel precursor peeling or delamination from the dried patch. The resulting hydrogel precursor structure provides a surface that can be applied to a wound, wherein the surface is completely or at least substantially covered with the hydrogel precursor, even when broken. The hydrogel precursor structure may be referred to as a layer, or as a term reflecting its ability to penetrate a substrate to form a cohesive hydrogel precursor or a coating of more complex structures, for example a cohesive hydrogel precursor structure, a cohesive hydrogel precursor network or a cohesive network, which are used interchangeably herein.

In principle, the compression of the gelatin sponge can be carried out in various ways, for example by placing the patch between two plates which are tightened over the structure. A convenient way of applying the compression is to pass the patch through calender rollers. The gap of the calender rollers can be set to achieve the desired compression. The compression using rollers is also convenient in a process flow approach, and also for breaking up the precursor layer by applying a shear force. The desired compression can be gradually achieved by repeatedly applying the rollers. The first compression without the precursor layer can be carried out with a larger roller gap than the subsequent compression through the rollers with the precursor layer.

In relation to the hydrogel precursor layer, the protected nucleophilic precursor generally has an acidified amine group. For example, the amine can react with a strong acid, such as hydrochloric acid, and the chloride ion or other corresponding conjugate base can remain bound to the precursor. The acidification of the amine stabilizes the precursor layer by inhibiting the crosslinking reaction until the amine can be deprotonated. With this precursor selection, the resulting patches can be kept stable in a dry storage environment for a considerable period of time. The nucleophilic precursor generally has multiple functional groups, and using three or more functional groups can result in a higher crosslinking structure. The nucleophilic precursor can have a hydrophilic core, which can be highly branched with pendant amine groups. Low pH buffers may not destabilize the acidified amine groups.

The electrophilic precursor has an electrophilic group that can undergo an addition reaction with an amine to form a covalent crosslink. The electrophilic group generally reacts only with an amine group and does not react with a protonated amine group, i.e., an ammonium acid conjugate. The electrophilic precursor has a number of functional groups, and if it has three or more functional groups, it can form a highly crosslinked hydrogel. The electrophilic group is generally attached to a hydrophilic core such as polyethylene glycol, and can be appropriately branched to form a desired degree of crosslinking.

The electrophilic precursor and the protected nucleophilic precursor can be designed to have a flow temperature lower than the decomposition temperature of one of the two precursors. Thus, the two compounds can be used to form a molten mixture. The molten mixture can be formed into a good mixture. The molten mixture can then be processed to form a patch. If the precursor layer includes a sublayer, the sublayers can be applied sequentially one on top of the other. The sublayer can be composed of the mixture or of one of the precursors. In general, processing can be performed under low humidity conditions to reduce moisture absorption from the surrounding atmosphere. The molten mixture can be formed directly into the patch coating, but the molten mixture can in principle be solidified for subsequent processing. For example, the molten mixture can be slot coated onto the substrate, but extrusion, screen printing, spraying, or other similar processing techniques can also be used. Slot coating or other coating techniques can be performed on the substrate sheet to allow efficient processing. After the coating has solidified, the coated sheet can be cut into the desired patch size. Alternatively, the coating can be formed on a pre-cut patch substrate. The patch may be distributed using appropriate packaging to maintain its dehydrated state.

In some embodiments, the precursor may be dissolved in an inert organic solvent. Suitable solvents may be aromatic liquids or aprotic solvents, such as toluene, xylene, dimethyl carbonate, etc. In general, the solution may be highly concentrated to reduce solvent usage, as long as the fluid properties allow for appropriate processing. The coating approach for solvent-based deposition is generally the same as for melt mixtures, and the concentration may be adjusted appropriately to suit the particular deposition method.

The components of the patch tend to be hydrophilic and/or hygroscopic. Therefore, the synthetic or purchased components may be dried/desiccated prior to processing to form the patch. Some substrates may be lyophilized. In some embodiments, it may be desirable to have a hydration level of 5 wt. % or less or even lower. Processing may be performed in a controlled atmosphere using heat and vacuum in dry air, nitrogen or a similar atmosphere. Processing may include a sweep technique combining heat with a limited flow of an inert drying gas under partial vacuum to enhance drying. Conditions for moisture reduction may be provided. After the patch is formed, it may be packaged in a moisture-proof packaging material in dry air. For example, the patch may be sterilized using ethylene oxide gas during packaging or using radiation after packaging. Sterilization may be performed under conditions that do not induce significant crosslinking.

The hydrogel patches described herein are particularly suitable for use as implantable hemostatic patches that can be absorbed over a suitable period of time, from several days to a month or more. The hydrogel patches can be used to control bleeding or to close wounds during open or laparoscopic surgery. The hydrogel patches can generally be used in any wound healing context, and can also be used in non-implantable superficial placements. The properties of rapid closure, good adhesion, and controllable absorption time provide desirable properties for a variety of applications.

Patch structure and hydrogel precursor

The hydrogel precursor patches described herein generally comprise a substrate and a hydrogel precursor layer that is a mixture or sublayer on the substrate surface, but typically penetrates to some extent into the substrate. The substrate can be selected to suit the desired application of the patch. Typically, the substrate is absorbable and the substrate can be absorbed in situ upon contact with a patient within a reasonable time. The patch can be suitable for implantation in a patient, in which case the substrate is generally absorbable. The precursor is generally substantially non-crosslinked and is mixed within the layer. The layer can be uniform or varied over the substrate. The precursor is selected to crosslink relatively quickly upon exposure to physiological solutions or tissues. The patch can be suitable as a hemostatic patch to help control and limit bleeding.

Prior to application of the patch, the hydrogel precursor in the layer on the substrate is substantially uncrosslinked. While precise quantification may not be practical, the concept and clear importance of satisfying this condition are quite clear. First, the chemical reaction is designed such that the amine groups are protected by acid modification, thereby blocking the nucleophilic reaction, thereby preventing crosslinking. The significant crosslinking causes the various precursor molecules to be bound together in a network structure. At a certain level of crosslinking, the material no longer has independent precursor molecules, but essentially becomes a cohesive mass of material linked by covalent bonds. This process is evaluated in the context of gelation, and the cohesive mass is referred to as the resulting gel, i.e., the hydrogel. As the degree of crosslinking of the hydrogel precursor approaches complete crosslinking over additional time beyond gelation, the gel becomes stronger and more rigid. The gelation time (or gel time) can be measured, for example, as described below. Conversely, in the intermediate stages prior to gelation, some crosslinking occurs, which alters the properties and thus the behavior of the composition. When the precursor is substantially uncrosslinked, the properties of the fully hydrated precursor are not significantly changed, and the flow and rheological properties show no measurable change in the precursor composition compared to the formed uncrosslinked composition, although these properties can change rapidly once crosslinking begins.

FIG. 1A illustrates the structure of one embodiment of a hemostatic patch. The hemostatic patch (100) has a substrate (102) and a precursor layer (104). The substrate (102) can be a gelatin substrate or other suitable substrate as described below. For example, the substrate (102) can be a gelatin substrate without added blood components such as fibrinogen or thrombin or platelets. In some embodiments, the substrate (102) is porous and absorbable. In additional or alternative embodiments, the substrate (102) is biodegradable. Typically, the substrate is relatively thin, with an average thickness of less than 1 cm, and the patch area can be appropriately selected to suit a particular application.

The precursor layer (104) can be a mixture of an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor. Alternatively or additionally, the precursor layer (104) can be comprised of a sublayer of an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor, which may or may not comprise a mixture, but generally has an interface of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor along the sublayer. In some embodiments, the sublayer, which is applied as a liquid to the substrate, forms a single homogeneous layer on the substrate after cooling and/or drying. In other embodiments, the sublayer forms a continuous layer having a compositional gradient. FIG. 1B shows an alternative structure of a hemostatic patch. A hemostatic patch (150) has a substrate (152) and a precursor layer (154). The precursor layer (154) is comprised of a stack of sublayers (160 and 164). The sublayers (160 and 164) are in direct contact with each other. In some embodiments, the sublayer (160) is a sublayer of an electrophilic hydrogel precursor and the sublayer (164) is a sublayer of a nucleophilic hydrogel precursor. In other embodiments, the configuration of the sublayers is reversed, such that the sublayer (160) is a sublayer of a nucleophilic hydrogel precursor and the sublayer (164) is a sublayer of an electrophilic hydrogel precursor. In some embodiments, the precursor layer (154) is comprised of three or more alternating sublayers, e.g., sublayer (160)/sublayer (164)/sublayer (160), wherein adjacent sublayers are in direct contact with each other. As used throughout this specification, direct contact between hydrogel precursors refers to more than accidental or unintended contact, and involves significant surface area of each component along the extended dimensions of the layer and generally involves interactions between layers. The multiple sublayers may have the same or different thicknesses. In some embodiments, the precursor layer (104/154) has a visualizing agent so that the precursor layer (104/154) is visually distinguishable from the substrate (102/152). In a preferred embodiment, the precursor layer (104/154) has a blue or green color due to the presence of a dye.

FIG. 1C shows another structure of a hemostatic patch. A hemostatic patch (170) has a compressed substrate (172) and a precursor layer (174). Typically, the compressed substrate (172) is porous and absorbent. In some embodiments, the precursor layer (174) penetrates into the porous structure of the compressed substrate (172). The precursor layer (174) can be manufactured with the same composition and/or have the same sublayer structure as described above for the precursor layer (104) and/or the precursor layer (154). In some embodiments, the precursor layer (174) has a fracture, such as a microfracture and/or a crack. FIG. 1D shows another structure of a hemostatic patch. A hemostatic patch (180) has a compressed substrate (182) and a cohesive hydrogel precursor structure (184) having a fractured surface (186). Typically, the cohesive hydrogel precursor structure (184) has a precursor material embedded in a substrate material and provides a surface located on one side of the compressed substrate (182). In some embodiments, the surface area of the compressed substrate (182) associated with the cohesive hydrogel precursor network (184) is completely coated with the hydrogel precursor mixture. Typically, the compressed substrate (182) is porous and absorbent. Typically, the hydrogel precursor has good cohesion within the cohesive hydrogel precursor structure (184) to prevent collapse or loss of the precursor material even if the surface is broken. Typically, the hydrogel precursor within the cohesive hydrogel precursor structure (184) has good adhesion to the compressed substrate (182). In some embodiments, good cohesion and/or good adhesion may be characterized by the cohesive hydrogel precursor structure (124) being resistant to peeling during handling and/or further processing. Handling and/or further processing may include calendering to break up the surface (186) of the cohesive hydrogel precursor structure (184), as well as handling after patch formation, including, for example, bending, folding, packaging, and/or shipping. Typically, the compressed substrate region (183) opposite the cohesive hydrogel precursor structure (184) is free of hydrogel precursor. The cohesive hydrogel precursor structure (184) may be prepared by applying a mixture of electrophilic hydrogel precursors and nucleophilic hydrogel precursors to a porous hydrophilic substrate, such as a cross-linked gelatin substrate, or by applying the precursors as separate precursors in adjacent layers that may be mixed to some extent during application but are otherwise adjacent along the patch region. In some embodiments, the porous hydrophilic substrate has a broken cell structure.

In some embodiments, the application of the precursor material is performed using a porous hydrophilic substrate, e.g., a print head, under compression to inject the hydrogel precursor into the substrate. In some embodiments, the cohesive hydrogel precursor structure (184) has a surface that is coincident with one surface of the substrate (182). In other embodiments, the cohesive hydrogel precursor structure (184) has a surface that extends beyond the surface of the substrate (182) opposite the compressed substrate region (183). The hydrogel layer (174) ( FIG. 1C ) extends beyond the surface of the substrate (172) and may be considered one embodiment of the cohesive hydrogel precursor structure (184). In some embodiments, the porous substrate is prepared by calendering prior to printing. In some embodiments, the cohesive hydrogel precursor structure (184) has fractures, such as microfractures and/or cracks. The compressed substrate (172/182) may be a cross-linked gelatin substrate. In some embodiments, the compressed substrate (172/182) is a cellular sponge substrate. In some embodiments, the compressed substrate (172/182) is a compressed gelatin substrate, such as formed by compression of a rigid and/or cross-linked gelatin substrate. In additional or alternative embodiments, the compressed substrate (172/182) is biodegradable. Generally, the hemostatic patch (170/180) is relatively thin, having an average thickness of not more than 1 cm, and is relatively flexible. The thickness, width, and length of the patch can be appropriately selected to suit a particular application. The presentation of FIGS. 1a, 1b, 1c, and 1d as separate drawings does not imply that the features of the individual drawings cannot be suitably combined or interchanged in the overall discussion of this specification.

The size of the hydrogel precursor patch can be appropriately selected for the appropriate application. Furthermore, the overall thickness is divided into the substrate thickness and the hydrogel precursor thickness. In this paragraph and the following paragraph, the dimensions refer to the dimensions of the dry patch, and the swelling due to hydration is discussed in more detail below. The area of the patch is generally not particularly limited and can be selected based on the location where the patch is intended to be placed. For commercial applications, various sizes may be distributed for the user to choose from. As a practical constraint, the patch area should generally not exceed 20 centimeters (cm) x 20 cm for human patients, but larger patches may be used, and within this range, smaller sizes such as 5 cm x 5 cm, 10 cm x 5 cm, or 2 cm x 4 cm may be selected. Specific dimensions may be suggested for specific applications as a matter of practice. Since various sizes are available, the medical professional can select the desired size. Typically, the patch can be cut to the desired size using tools available in the operating room environment and applied to the specific situation encountered.

The thickness of the patch can vary depending on the balance between the ability of the patch to conform to the application site and the ability to absorb a desired amount of fluid over a period of time. A thicker patch is less flexible and may take longer to absorb moisture and break down, but a thicker patch can absorb more blood and other fluids. Likewise, a thinner patch is generally less absorbent, more flexible, and may break down more quickly, resulting in a shorter duration. The crosslinked hydrogel precursor layer generally provides all or most of the adhesive strength of the patch when it is first applied. The substrate can be selected to provide a significant amount of fluid absorption. In some embodiments, the patch can have a dry average thickness of from about 0.25 mm to about 10 mm, in further embodiments from about 0.3 mm to about 9 mm, in further embodiments from about 0.35 mm to about 8 mm, and in other embodiments from about 0.4 mm to about 6 mm. The substrate (102/152/172/182) can have an average dry thickness of no more than about 10 mm, and in some embodiments from about 0.2 mm to about 8 mm, in further embodiments from about 0.25 mm to about 7 mm, and in further embodiments from about 0.3 mm to about 5.5 mm. The precursor layer (104/154/174) can have an average thickness of about 25 microns to about 2 mm, in further embodiments from about 30 microns to about 1.75 mm, and in other embodiments from about 40 microns to about 1.5 mm. The precursor layer can partially penetrate the substrate. In some embodiments, a substantial portion of the precursor layer remains on the substrate to provide a dry precursor layer for patch application. To estimate the average precursor layer thickness, the precursor content per unit surface area (g/cm2) can be divided by the precursor density (g/cm3) to calculate the average thickness, or the precursor layer can be applied to a non-porous substrate and the dry average thickness can be measured to provide an accurate estimate of the thickness, since the relatively dense nature of the precursor layer should not be substantially altered by the substrate. Generally, the patch will have these ratios of substrate to hydrogel precursor coating thickness, but in some embodiments it is preferred that the dry substrate be at least as thick as the dry hydrogel precursor layer, and in further embodiments greater than or equal to about 60%, in some embodiments from 65% to 95%, and in other embodiments from about 70% to about 90% of the dry patch thickness. For ease of measurement, the substrate thickness includes all hydrogel precursor that penetrates the substrate. A person skilled in the art will recognize that additional ranges of dimensions and thicknesses are contemplated within the explicit ranges above and are within the scope of the present invention. In general, the hydrogel precursor layer can be added without significantly damaging the porosity and absorbency of the substrate material.

More generally, in addition to gelatin-based substrates, substrates suitable for patches can in principle be formed from natural materials, synthetic materials or combinations thereof. Synthetic materials for absorbent substrates include, for example, polyesters, polyurethanes, high molecular weight polyethylene oxide (PEO) or other suitable synthetic polymers. Absorbent polyesters include, for example, polylactic acid, polyglycolic acid or copolymers thereof. High molecular weight PEOs can be slowly dissolved in water. Natural materials are usually processed appropriately to be incorporated into medical products and are therefore usually modified from their natural form to varying degrees. Nevertheless, natural materials can provide the desired properties suitable for substrates, such as high absorbency in aqueous solutions and degradation in vivo within a reasonable period of time. Suitable natural materials include, for example, polysaccharides and substances derived from extracellular matrix proteins. For example, polysaccharides, which are derivatives of cellulose, pectin, hyaluronic acid or chitosan, can be used to make absorbent sheets. Commonly used materials are cellulose forms, including ester and ether derivatives such as cellulose acetate or ethylcellulose. Oxidized cellulose is a substance that helps to stop bleeding, but it is generally known to be poorly absorbed and may cause postoperative complications; hydroxycellulose, nitrocellulose, or other forms may be suitable.

Collagen is an extracellular matrix protein and in its natural form can be found in triple-stranded fibers. Purified collagen can take a variety of forms, and gelatin is a partially hydrolyzed form of collagen. Collagen can be derivatized by other methods, if desired. Highly absorbable and absorbable collagen sponges have been developed, which can be used as hemostatic agents on their own. For example, commercial versions are sold by Becton, Dickinson and Company under the trademarks Avitene™ MCH and Avitene™ Ultrasponge. Gelita Medical GMBH sells gelatin (collagen-based) hemostatic materials that can provide the basis for patch substrates. Custom substrates can be formed using commercially available medical collagen or gelatin (e.g., Gelita Medical or other suppliers), formed into sheets, and optionally crosslinked, such as with glutaraldehyde, followed by drying, such as by freeze drying. Crosslinking can stabilize collagen, while strong chemical crosslinking can significantly increase its durability.

Gelatin can be thermally cross-linked and/or chemically cross-linked using, for example, formaldehyde or glutaraldehyde to mechanically stabilize the material suitable for the substrate. Gelatin is a hydrolyzed form of collagen. The length of thermal cross-linking affects the duration. Without wishing to be bound by theory, it is thought that thermal cross-linking can affect the cross-linking of adjacent suitable groups within the structure. In contrast, chemical cross-linking can form more complex cross-linked structures that can provide significant entropic stabilization. Sufficiently extensive chemical cross-linking can produce essentially permanent/non-degradable materials. Chemically cross-linked collagen has been used for decades in artificial tissues, heart valves, and other prosthetics. Prior to thermal cross-linking, the gelatin is placed into the desired shape and then heated, for example, in an oven. Typically, the thermal crosslinking can be performed at a temperature of from about 100° C. to about 200° C., in further embodiments at a temperature of from about 120° C. to about 180° C. for from about 15 minutes to about 4 hours, and in further embodiments for from about 25 minutes to about 3 hours. Those skilled in the art can adjust the time and temperature to achieve the desired properties (e.g., porosity, mechanical stability, duration after implantation into a living body), as described in detail below. When using a thermal crosslinked gelatin material, the substrate can be a foam, a nonwoven tufting material, or a nonwoven felting material. Those skilled in the art will recognize that additional temperature and time ranges within the ranges specified above are contemplated and are within the scope of the present invention.

Commercially available gelatin sponges are available which may or may not be foamed and chemically cross-linked. The gelatin sponge in the examples is a foamed, non-cross-linked commercial material. The use of non-cross-linked gelatin avoids concerns that potentially toxic chemicals used in cross-linking may be released. The resulting foamed gelatin material has a porous structure with a sponge-like cell structure. The density and pore size can be controlled through processing parameters. The commercial material can be designed to have adequate absorbency to absorb fluids from a wound. Compression of the gelatin substrate has been shown to significantly improve flexibility while not significantly changing absorbency. Absorbency can be assessed by soaking the sponge in saline solution and assessing the weight after the sponge has been soaked and has reached a plateau in liquid absorption. The denser the substrate, the longer it may take to reach a plateau in swelling, but for highly porous gelatin sponges, plateau may be reached sooner, typically with most swelling being achieved after about 10 minutes. It is acceptable to wait longer to measure after the swelling plateau has been reached, but measurements may be taken after 24 hours if desired to comfortably capture the swelling, but swelling measurements should be made before the hydrogel has significantly degraded. For highly foamed gelatin sponges, a significant portion of the swelling may occur in less than a minute, and denser substrates may not remain at plateau for significantly longer. The substrate typically absorbs at least about 100% of its dry weight in liquid, and in some embodiments at least about 150%, in further embodiments at least about 200%, in other embodiments at least about 250%, and in further embodiments at least about 350%, of its dry weight in liquid, and typically the biocompatible substrate can absorb from 100% to 2500% by weight of water, relative to the dry patch weight. In general, the uncompressed initial volume allows for some expansion, providing an approximate upper limit on the expanded weight of the solvent. In some embodiments, the compressed substrate (without the hydrogel precursor layer) can absorb greater than about 80% of the liquid as the uncompressed substrate, in other embodiments greater than about 90%, and in some embodiments greater than about 92.5% of the liquid as the uncompressed initial substrate, suggesting that the compressed substrate can swell close to its uncompressed value. By way of example, the compressed substrate absorbs greater than 98% of the liquid as compared to the uncompressed substrate material. A person skilled in the art will recognize that additional ranges are contemplated within the explicit ranges above and are within the scope of the present invention.

With respect to the improved flexibility after compression, this can be assessed by comparison to the corresponding substrate material without compression. An uncompressed thin material may be more flexible than a thicker material, but the absorbency is roughly reduced due to the change in thickness and the resulting mass loss. Therefore, it is appropriate to compare shapes with roughly the same absorbency. Since flexibility depends on the initial thickness of the substrate and the material used to form the substrate, attempts to quantify the improved flexibility may not be very meaningful. The flexibility of the substrate can be qualitatively compared by wrapping the substrate around a mandrel, in which case a more flexible substrate can generally be wrapped around a narrower mandrel without breaking. Thus, in some embodiments, a compressed substrate can be bent around a mandrel having parallel folded sides with a diameter of 5 mm. However, a compressed substrate may lose mechanical strength. With respect to the force to bend the material, this force (the bending strength) is reduced, making the material easier to bend or fold. Since the columnar strength is reduced, squeezing the two opposite sides requires less force to break the material, which is a natural result since the cells are already destroyed. The hydrogel precursor layer provides mechanical stability to the compressed substrate without a significant decrease in flexibility along the axis parallel to the calendar roll due to destruction of the hydrogel precursor layer.

The compression of the substrate may be performed in one or more compression steps. In a particularly interesting embodiment, at least the last compression is performed after the precursor layer has been added to the top of the substrate, and at least one compression step is performed prior to deposition of the precursor layer to provide greater penetration of the precursor layer while leaving a top surface of the precursor layer. Subsequent compression steps may be performed at increasingly smaller compression thicknesses, although due to some reactivity of the material, subsequent compressions may be performed at the same or potentially slightly wider compression thicknesses. The initial gelatin sponge thickness provides a fundamental parameter for the final assembled structure, which is modified by processing that collectively determines the properties. The final compression is typically performed at intervals of about 85% or less of the initial substrate average thickness, in embodiments at intervals of about 65% or less of the initial substrate average thickness, in some embodiments at intervals of about 55% or less of the initial substrate average thickness, and in further embodiments at intervals of about 20% to about 50% of the initial substrate average thickness. In some embodiments, the compression range can have a lower limit of 5%, 10%, 15%, 20%, 25% or 30% and an upper limit of 85%, 75%, 65%, 60%, 55%, 50% or 45%, and the range can include combinations of any of these lower limits with any of these upper limits. The substrate material can have some rebound due to compression, but it can be desirable to maintain at least about 40% of the compression step (with the rebound being no greater than about 60%), so that compressing to 2 mm to 1.5 mm will result in a final average thickness of no greater than about 1.8 mm, without making the gelatin too elastic, although in some embodiments the rebound can be 100% even without any net compression. Typically, the rebound can be from about 0% to about 100%, in some embodiments from about 10% to about 90%, in other embodiments from about 15% to about 80%, and in other embodiments from about 20% to about 70%. A person skilled in the art will recognize that additional ranges of relative compression and rebound within the above stated ranges are contemplated and are within the present invention.

In principle, various approaches may be suitable for applying compression, but the use of calender rollers, etc., provides shear in addition to compression, unlike the use of flat plates. The shear along the edges passing through the rollers provides additional forces to fragment the cell structure of the sponge. In particular, when the hydrogel precursor layer is on a substrate, the shear forces tend to crack the hydrogel precursor layer, which contributes to flexibility and faster hydration when in contact with fluids. The nature of the cracking generally depends on the amount of compression and the properties of the material, but the cracking or fracture may or may not occur throughout the entire thickness of the hydrogel precursor layer. Since the fractures are randomly distributed, it is not feasible to characterize the fractures precisely, but in some embodiments there is typically a noticeable fracture within each square centimeter of the finished structure. Calender rollers are also particularly suitable for process flow in continuous production.

Calender rollers and related transport systems are well known in many industries. Calender rollers are widely used in polymer processing and food processing, and some of the equipment may be shared by other industries. For convenience, pasta rollers are used in the examples. Commercial calender rollers are typically thickness-adjustable. Multiple calender rollers may be arranged in series to perform sequential calendering steps, such as reducing the thickness, but in other production configurations, the same calender rollers may be used sequentially with appropriate adjustments between runs. As mentioned above, the hydrogel precursor layer may be formed prior to the calendering step, e.g., prior to the last calendering step. The formation of the hydrogel precursor layer is described in more detail below. Although roll-to-roll processing is in principle possible, the foamed gelatin is typically formed into blocks or other fixed shapes that can be cut to desired dimensions (including thickness). Thus, the processing system may be designed to handle gelatin sponge sheets. In some embodiments, the sheets may be relatively large for subsequent cutting into individual patches for packaging. Cutting the sheet into individual sheets potentially discards the edge portion of the larger sheet, which may result in less uniformity depending on process considerations.

Since the components of the patch tend to be hydrophilic and/or hygroscopic, the components may be dried/desiccated prior to processing to form the patch. Suitable drying techniques may include, for example, vacuum drying, thermal drying, desiccant drying, freeze drying, or the like, or combinations thereof. It may be desirable to maintain the hydration level below 5 wt% water, in further embodiments below about 3 wt%, in other embodiments below about 2 wt%, or in some embodiments significantly lower. The moisture content may be determined by coulometric titration (Karl Fischer) or loss on drying. Those skilled in the art will recognize that additional ranges of moisture content are contemplated within the above-mentioned ranges and are within the scope of the present invention.

The hydrogel precursor can be selected to provide desirable absorbency and crosslinking properties when contacted with a physiological solution, and can remain stable as a coating under dry, typically refrigerated conditions for a suitable shelf life, for example, at least 2 months, and in some embodiments at least about 6 months. The nucleophilic group can be a protonated amine, wherein the acidic amine in its protonated form is protected from crosslinking. Suitable electrophilic groups crosslink with unprotonated amines when in contact with the same phase, whether co-molten in the mixture or dissolved in the solvent, typically at a pH of about 7.1 or greater, and deprotonate the initially protonated amine.

With respect to buffers, hydrogel precursors are not considered buffers, whether or not the pH is changed, and in principle can provide some degree of buffering. The amine precursors are provided in an acidified form, and the acidic protons act as protective groups that prevent crosslinking. Upon contact with body fluids at physiological pH, the acidified amines are deprotonated and can crosslink with the electrophilic precursors. The non-crosslinked precursor layer may not require significant amounts of buffer, and desirable patch performance is observed even without the addition of buffer. The buffers can be considered as Brønsted bases, which are typically anions (B ^- ) corresponding to weak acids (HB). Anions corresponding to strong acids, such as halide anions, do not act as water-soluble buffers, and the amine precursors are typically provided as HCl salts or similar strong acid analogues.

In general, pH is used to control the crosslinking reaction, and the amine is provided in an acidified form that inhibits crosslinking. Therefore, if a high pH buffer is not used in the precursor layer, premature crosslinking reaction through activation by the buffer is avoided. When physiological fluids penetrate the patch during use, the pH change induced by the physiological fluids rapidly deprotonates the amines and induces crosslinking. Since the precursors are mixed or in direct contact with the dry patch, the precursors can be crosslinked quickly, and the initial crosslinking density is relatively high, which provides good adhesion without having to wait longer for more complete crosslinking. The gelation time is described in detail below.

In hydrogel systems, a functional group suitable for crosslinking the monomers to form an adhesive patch in situ may be advantageously used, including macromonomers typically containing an electrophilic group that exhibits activity toward amine functionalities, as described below. Thus, a multicomponent hydrogel system may be capable of spontaneously crosslinking when the components are contacted with a physiological fluid and activated, but wherein two or more of the components are suitably stable for a reasonable process time before activation by the physiological fluid. Such a system comprises, for example, a monomer (typically, but not necessarily, a macromonomer) having two or more amines on one component and a macromonomer having two or more electrophilic groups, such as an N-hydroxysuccinimide ester-containing moiety on the other component. The N-hydroxysuccinimide ester functionality catalyzes amide bond formation upon reaction with an amine and has been used in other medical hydrogels, although other suitable electrophilic precursors are described below. N-hydroxysuccinimide esters are typically suspended in a hydrophilic core.

The hydrogel precursors can have crosslinks that are activated by physiological fluids that contact the precursor after delivery. The hydrogel precursors described herein can be designed to hydrate relatively quickly. The properties of the hydrogel and precursor solutions are described in detail below. Parameters that affect the properties include: functional group chemistry, crosslink density/molecular weight of the monomers, monomer composition, substrate composition, and patch architecture.

The crosslink density of the resulting biocompatible crosslinked polymer is controlled by the overall molecular weight of the macromonomer and the number of functional groups available per molecule. A lower molecular weight between crosslinks, such as 600 Da, results in a higher crosslink density compared to a higher molecular weight, such as 10,000 Da. High molecular weight macromonomers with significant branching provide desirable gelation times, in some embodiments greater than 2500 Da, to obtain elastic gels. In certain embodiments, the nucleophilic acid conjugated polymer (including the amine) is not significantly lower in molecular weight than the electrophilic polymer. In some embodiments, they are the same size or larger.

Crosslink density can also be controlled by the ratio of nucleophilic to electrophilic groups in the mixed precursor materials. For dry solid precursor layers, gelation time varies greatly with hydration time, as crosslinking reactions can occur in water and amines can be deprotonated and used for nucleophilic substitution. A rapidly hydrating substrate can aid in hydration of the dried hydrogel precursor, and the size of the hydrophilic core of the precursor molecules can affect hydration time. Without wishing to be bound by theory, it is thought that longer gelation times are related to slower diffusion of physiological fluids into the patch or slower diffusion out of the patch where the acid conjugate species are placed in situ. Another way to control crosslink density is to adjust the stoichiometry of the nucleophilic to electrophilic groups. A 1:1 ratio of electrophilic to amine groups will yield the highest crosslink density, but the electrophilic groups in the precursor can in principle react with amines in proteins in physiological solution as well as in tissues. In the examples, desirable performance was obtained when the functional group ratio was 1:1.

Monomer

Monomers capable of being crosslinked can be used to form biocompatible structures, e.g., implants. As noted above, the monomer can be a macromonomer, and the macromonomer may or may not be a polymer. As used herein, the term polymer refers to a molecule formed of at least three repeating groups, and which can then have reactive functional groups attached to the polymer. The term "reactive precursor species" generally refers to a polymer, functional polymer, macromolecule, or small molecule that can participate in a reaction to form a network of crosslinked molecules, e.g., a hydrogel. As noted above, to form a rapidly crosslinking hydrogel precursor system, the monomer is typically, but not necessarily, a macromonomer, since macromonomers generally allow for faster hydration and faster deprotonation of the amine.

For example, the monomers can include biodegradable, water-soluble macromonomers as described in U.S. Pat. No. 7,332,566 to Pathak et al., entitled “Biocompatible Crosslinked Polymers With Visualization Agents” (hereinafter the “‘566 Patent”), which is incorporated herein by reference. These monomers are characterized by having at least two polymerizable groups, which may or may not be separated by at least one degradable region. Upon crosslinking, the resulting polymers form a cohesive hydrogel that persists indefinitely or until removed by degradation, which may include enzymatic reactions or hydrolysis. Typically, the macromonomers are formed of a core of a water-soluble, biocompatible polymer, such as a polyalkylene oxide, such as polyethylene glycol, which may be surrounded by a hydroxy-carboxylic acid, such as lactic acid, to form a degradable ester or a non-degradable amide. Suitable monomers should be biocompatible and non-toxic, and should also have some elasticity after crosslinking or curing. In the case of electrophilic compounds or compounds having amine groups, the core of the compound can have multiple arms or branches, each having a functional group suitable for crosslinking. PEG-based polymers having three or more arms are typically star polymers in which the PEG polymer arms extend from a branched core. As mentioned above, polyethylene glycol (PEG)-based monomers are established medical hydrogel precursors, and precursor compounds are commercially available with a variety of numbers of arms, molecular weights, and functional groups.

The nucleophilic functional group is typically an amine group. The amine group can be protonated as a protecting group or gate to control crosslinking. The nucleophilic amine group of the precursor can be designed to be substantially deprotonated at physiological pH values, such as about 7.1 to about 7.6 pH units, although the blood and tissues of healthy individuals typically have a narrower pH range. While macromonomers are exemplary and provide desirable properties, trilysine has been used as a polyamine monomer in medical hydrogels and similar compounds may also be used. The electrophilic functional group can be selected to undergo an addition reaction with the amine to form a crosslink. N-hydroxylsuccinimide ester is a preferred electrophilic group, but other suitable groups are described below. One or both of the functional groups can be attached to the hydrophilic core, which can help provide the desired swelling properties to the liquid upon hydration. In some embodiments, the polymer may have a hydrolytically biodegradable moiety or linkage, such as an ester, carbonate or other suitable linkage, but may additionally or alternatively have an enzymatically degradable linkage. Some of these linkages are well known in the art and are derived from alpha-hydroxy acids, their cyclic dimers (anhydrides), or other chemical species used to synthesize biodegradable moieties, such as glycolide, dl-lactide, l-lactide, caprolactone, dioxanone, trimethylene carbonate or copolymers thereof. In particular, the electrophilic monomer may conveniently be provided with a degradable linkage.

Typically, the monomer providing the electrophilic functional group and the monomer providing the amine functional group are macromonomers to provide faster hydration of the dried precursor layer. Typically, the macromonomer has a biologically inert and water-soluble core and reactive functional groups for crosslinking. When the core is a water-soluble polymer region, the polymers that can be used can be natural or synthetic polymers. Suitable polymers for the core can include polyethers, such as polyethylene glycol ("PEG"), polyethylene oxide ("PEO"), polyethylene oxide-copolymerized polypropylene oxide ("PPO"), co-polymerized polyethylene oxide block or random copolymers, poloxamers, such as Pluronic® F-127; as well as polyoxazolines, polyvinyl alcohol ("PVA"); poly(vinyl pyrrolidinone) ("PVP"); and polysaccharides, such as hyaluronic acid, chitosan, dextran or digested cellulose and derivatives thereof. Based on our extensive experience with existing medical products, star-branched polyethers, more particularly polyethylene glycols (also called poly(oxyalkylene)s or poly(ethylene glycols)), are particularly suitable. The acidified amine or electrophilic groups can be located at the end of each arm or as part of one of them. For PEG precursors, a common notation in the medical hydrogel field is the number of arms together with the molecular weight and the functional group on the arms, e.g. a four-armed PEG having a molecular weight of 15,000 daltons and the acidified amine containing chloride ion is 4A15K NH2-HCl, while an eight-armed PEG having a molecular weight of 20,000 daltons and containing an N-hydroxysuccinimidyl ester functional group is 8A20K NHS ester.

PEG-based hydrogels are widely used in medical products. As a result, they are widely accepted, and medical PEG monomers with various functions are commercially available. Polyoxazolines have attracted attention as a potential desirable alternative to PEG-based products. Poly(2-oxazoline) has the structure -(CH ₂ CH ₂ N(COR))-, where R can be H, an alkyl group, or other functional groups. Amine-terminated poly(2-ethyl-2-oxazoline) is available from Sigma-Aldrich. Terminal-functional monomers do not allow crosslinking, but multifunctional electrophilic monomers with three or more functional groups can realize crosslinking. Poly(2-R-2-oxazoline) having 25% side chains filled with N-hydroxylsuccinimide (NHS)-ethyl groups was synthesized as described in published U.S. Patent Application No. 2019/0125922 to Bender et al., entitled “Tissue-Adhesive Porous Hemostatic Product,” which is incorporated herein by reference.

It has been found that hydrogels formed from macromonomers with longer distances between cross-links are generally softer, more flexible, and more elastic. Thus, in the polymers of the '566 patent, the longer the length of the water-soluble segments, such as polyethylene glycol, the more elastic the polymer tends to be. The molecular weight of the hydrophilic macromonomers used herein, e.g., macromonomers having a polyethylene glycol macromonomer core, is generally greater than about 2,000 Da, and in some embodiments ranges from about 2,500 Da to about 500,000 Da, in other embodiments from about 5,000 Da to about 250,000 Da, in further embodiments from about 7,500 Da to about 100,000, in still further embodiments from about 10,000 Da to about 50,000 Da, and in still other embodiments from about 15,000 Da to about 40,000 Da. PEG precursors in the lower part of this weight range can be liquids. As used herein, molecular weight (mass) is expressed in conventional units, equivalently in daltons or molar mass (grams/mole) (in both cases assuming the presence of natural isotopes), and in the case of polymers, molecular weight is generally reported as an average, where there is a molecular weight distribution. Those skilled in the art will recognize that additional ranges are contemplated within the above-mentioned ranges and are within the scope of the present invention.

The hydrogel precursor in the hydrogel precursor solution has a ratio of electrophilic functional groups to amine functional groups. The ratio of the functional groups can change the crosslinking density and the properties of the resulting hydrogel. Generally, if the ratio of the number of electrophilic functional groups to amines is 1:1, the hydrogel can be completely crosslinked if there is sufficient time and no constraints. In some embodiments, the ratio of nucleophilic functional groups to electrophilic functional groups is greater than 1. Generally, the ratio of electrophilic to nucleophilic functionalities can be from about 0.8 to 1.2, in further embodiments from about 0.9 to about 1.1, in further embodiments from about 0.95 to about 1.05, in other embodiments from about 0.98 to about 1.02, in further embodiments from about 0.99 to about 1.01, and in some embodiments from about 0.995 to about 1.005, but the ratio can be about 1:1. A person skilled in the art will recognize that additional ranges of ratios within the explicit ranges above are contemplated and are within the present invention.

The functional groups can be distributed in various ways to obtain the desired ratio of functional groups. The pendant functional groups extending from the core can be said to be connected to the arms of the precursor. The precursors generally have 2, 3, 4, 5, 6, 7, 8, 9, 10 or more arms. Generally, at least one precursor has at least 3 arms to obtain crosslinking, and precursors having 4, 6 or 8 arms can be convenient for obtaining the desired hydrogel properties. In order to adjust the functional group ratio to 1:1, the same molar amount of precursors having the same number of arms can be used, or the molar ratio can be adjusted accordingly if each precursor has a different number of arms. Thus, twice the molar amount of a 4-arm precursor can be combined with an 8-arm precursor to obtain a functional group ratio of 1:1. For weight ratios, the molar ratio can be appropriately adjusted depending on the relative weights, for example, combining twice the mass of 8-arm 10K MW (molecular weight 10,000) precursor with 8-arm 20K MW precursor will give a functional group ratio of 1:1. One skilled in the art can adjust these calculations to give other number ratios for functional groups.

Functional groups and cross-linking reactions

Although the crosslinking reaction is generally designed to occur in vivo, essentially physiological fluids and hydrated by aqueous fluids surrounding physiological conditions, medical procedures may involve some local dilution or modification of the physiological fluid from its pure natural state using disinfectants or other procedural means, without altering the basic processing of the hydrogel precursor. To aid hydration, the substrate may be wetted prior to application of the patch to the tissue, as described in detail below. Unless otherwise specified, the physiological fluids referred to herein are natural fluids that may undergo minor changes due to the medical procedure. Accordingly, the crosslinking reaction occurs "in situ," that is, at a local site, such as an organ or tissue of a living animal or human body. Because of the in situ nature of the reaction, the crosslinking reaction can be designed so that no unnecessary heat is released due to polymerization. Gelation times for preferred applications are described above, and complete crosslinking can generally be accomplished in a range of 2 minutes to 10 hours, although times outside this range may be acceptable. As the time it takes for cross-linking to complete increases, it can begin to compete with degradation time.

Certain functional groups, such as alcohols or carboxylic acids, generally do not react with other functional groups, such as amines, at physiologically acceptable pH. However, such groups can be made more reactive by using an activating group, such as N-hydroxysuccinimide or a derivative thereof. In general, a number of methods for activating such groups are known in the art. Suitable activating groups include, for example, carbonyldiimidazole, sulfonyl chloride, chlorocarbonate, aryl halides, sulfosuccinimidyl esters, N-hydroxysuccinimidyl esters (NHS), succinimidyl esters, succinimidyl amides, epoxides, aldehydes, maleimides, imidoesters, and the like. N-hydroxysuccinimide ester or N-hydroxysulfosuccinimide groups are preferred groups for crosslinking amine-functionalized polymers, such as amino-terminated polyethylene glycols ("APEGs"), because of their long-term use in approved products and their acceptance in medical implants. A further extensive discussion of general medical hydrogels is given in U.S. Patent No. 7,332,566 to Pathak et al., entitled “Biocompatible Crosslinked Polymer With Visualization Agents,” which is incorporated herein by reference.

Suitable nucleophilic functional groups are polymers in which a primary amine is conjugated to an acid. Therefore, the other functional group used for crosslinking is typically an amine. Amines are weak bases. In some embodiments, the acid conjugate is HCl, and an HCl chloride PEG amine, for example a PEG amine, is formed. The acid conjugate can be selected to roughly match the molar concentration of the amine. An advantage of the NHS-amine reaction is that it is kinetically fast to gel, typically within 10 minutes, more typically within about 1 minute, and most typically within about 30 seconds. The gelation time can be limited by the hydration time of the dried hydrogel precursor. Protonated amines are generally not amenable to nucleophilic substitution. Therefore, the precursor solution can be prepared at a pH suitable to substantially maintain the protonated amine prior to contact with the physiological solution.

The crosslink density of the resulting biocompatible crosslinked hydrogel is controlled by the overall molecular weight of the monomers and the number of functional groups available per molecule. A lower molecular weight between crosslinks, such as 2000 Da, results in a higher crosslink density than a higher molecular weight, such as 100,000 Da. Using higher molecular weight monomers results in more elastic hydrogels, while correspondingly using lower molecular weight monomers results in less elastic hydrogels. The properties of hydrogels can vary for different applications.

Another way to control crosslink density is to adjust the stoichiometry of the nucleophilic functional groups to the electrophilic functional groups. A 1:1 ratio can result in the highest crosslink density. Typically, over time, the hydrogel will cure to the point where all available crosslinking sites will form crosslinks. If the electrophilic and nucleophilic precursors are provided in equal amounts, almost all of the functional groups can be expected to form crosslinks after full cure. The highest crosslink density is typically achieved when the two types of agents are in equal amounts (or reaction equivalents). Varying the ratio of functional groups can result in somewhat different properties of the cured hydrogel. The crosslink density can vary not only depending on the ratio of precursor molecules, but also on the number of functional groups on the precursor molecules. If desired, the crosslink density can be varied by using a non-stoichiometric ratio of electrophilic and nucleophilic groups. The ratio of functional groups is described in more detail above.

Degradable or non-degradable connector

In general, it is desirable that the patch be degradable, and in some embodiments, degradable relatively quickly. Thus, the patch will not last indefinitely once implanted. In order for the patch to degrade, both the substrate and the hydrogel formed in situ must degrade. Depending on the application, it may or may not be desirable for the hydrogel to degrade, either by hydrolysis or biodegradation by enzymatic activity. However, for hemostatic patches, the patch is generally designed to degrade quickly after stably coagulating, so as not to last for long. When it is desirable that the biocompatible crosslinked hydrogel polymer be degradable or absorbable, one or more precursors having a degradable linkage between the functional groups can be used. An absorbable polymer used in the art is said to be biodegradable if it is absorbed under physiological conditions, whether or not it is degraded by biological action, such as enzymatic cleavage. The degradable linkage can optionally act as part of the water-soluble core of one or more precursors. Alternatively, or in addition, the functional groups of the precursors can be selected such that the reaction product between them produces a degradable linkage. In each approach, the degradable linker can be selected such that the resulting degradable biocompatible cross-linked hydrogel polymer will degrade or be absorbed within a desired time period. In other embodiments, the functional group and the linker to the functional group can be selected to resist degradation under physiological conditions, thereby substantially reducing or eliminating absorption of the patch.

Typically, a degradable linker is selected that degrades the hydrogel under physiological conditions into non-toxic products that are then eliminated from the patient by natural pathways. Examples of enzymatically hydrolyzable biodegradable linkers include peptide linkages that are cleavable by metalloproteinases or collagenases. Additionally, exemplary biodegradable linkers can be functional groups of the core polymer and copolymer, such as hydroxycarboxylic acids, orthocarbonates, anhydrides, lactones (amino acids, carbonates, phosphonates, or combinations thereof). In an illustrative embodiment, the degradable linker is an ester formed by a hydroxy-carboxylic acid moiety adjacent to an electrophilic group used for crosslinking. Esters can be gradually degraded by hydrolysis under physiological conditions, with the duration depending on the specific structure. To prepare non-degradable hydrogels, the ester formed by the hydroxy-carboxylic acid moiety can generally be replaced by an amide group that is not hydrolyzed under physiological conditions. Monomers having a PEG core are commercially available with N-hydroxysuccinimidyl electrophilic groups attached by amide linkages or ester linkages, for example, from Jenkem Technology, Texas. PEG-amines are also available from Jenkem in a variety of arm numbers and molecular weights. Preferred degradable electrophilic groups having an ester linkage include, for example, N-hydroxy succinimidyl succinate (SS), N-hydroxy sulfosuccinimidyl succinate, N-hydroxy sulfosuccinimidyl glutarate, succinimidyl glutarate (SG), succinimidyl adipate (SAP), succinimidyl azelate (SAZ), or mixtures thereof. Examples of rapidly degradable patches using SS linkers are described below. Mixtures of degradable and non-degradable linkages, such as the amides described above, can be used to control the duration, such as by forming oligomeric species that can be eliminated from the body.

Hydrogel and Patch Properties

Patch characterization can be performed in vitro under specific conditions, so that the properties are independent of biological conditions. Such evaluations help to describe patch properties that are important for practical in vivo use. In this regard, measurements of gelation time, swelling, substrate porosity, burst strength, and duration are described, and the results of such measurements are presented in the examples. However, for evaluating patch performance in practical applications, a protocol that provides appropriate limits for patch behavior under test conditions that mimic bleeding tissue can be used to provide a reproducible context for patch evaluation. The examples below present in vitro experimental results that are compared to those used in practical animal models. For dry patches, the density of the patch (substrate and precursor layer) can be from about 0.075 g/cm ³ to about 0.5 g/cm ³ . For the precursor layer alone, the density can be from about 0.050 g/cm ³ to about 0.450 g/cm ³ . Those skilled in the art will recognize that additional density ranges are contemplated within the above-mentioned ranges and are within the scope of the present invention.

The gelation time of the sample patch can be evaluated in a laboratory setting, which provides a reasonable estimate of the in vivo performance. The examples provide measurement results for specific samples. The gelation time is evaluated using a commercial texture analyzer. Texture analyzers are available from Texture Technologies Corp./Stable Microsystems, Ltd. (e.g., Model TA-XT Plus) and Brookfield Technologies (e.g., Model CTX Texture Analyzer). The system is designed to analyze food and soft medical materials. The instrument is initially calibrated using a standard test block according to the standard procedure for the instrument. A TA-005 probe (Texture Technologies) with a 1/4 inch diameter and flat surface (or hemispherical shape) can be used with a 5 kg load cell. The sample holder is heated to 37°C to track standard body temperature. The sample holder is a non-porous polymer foam block with a 1.5 mm hole in the center. An 8 mm diameter punch sample from the patch is placed centrally over the hole in the sample holder with the precursor layer facing down. To start the test run, the tester is started and 67 microliters (μl) of 37°C buffer (pH 8.0) is added to the center of the test sample for an 8 mm punch sample. The texture analyzer can be appropriately programmed to meet these parameters. The force required to deform the patch by 0.4 mm is determined as a function of time.

The time-dependent graph produces a characteristic curve. The patch starts out in a stiff dehydrated state, so the force is relatively high initially. After a few seconds, the patch absorbs water and the force becomes minimal. During hydration, crosslinking can be expected to begin and be processed early. As crosslinking continues, the force begins to increase, indicating that the crosslinking has reached a point where it determines the stiffness of the material. The time at which the force begins to increase is called the gelation time, which is the gelation point at which the gel begins to harden. In these systems, hydration occurs when the patch is hydrated, which is when the solid precursor hydrates and crosslinking begins. Therefore, the dissolution of the precursor is offset by the crosslinking. Once hydration is initiated, the solid softens until crosslinking is sufficiently advanced and the hydrogel begins to harden. The gelation process has different characteristics than solution-based hydrogel systems that start with dissolved precursors. After gelation begins, the force continues to increase as crosslinking continues. Measurements are made three times on three equal punches from the same patch, and the results are averaged. For the patches described herein, the gelation time is typically no longer than about 5 minutes, in further embodiments from about 3 seconds to about 3 minutes, in some embodiments from about 4 seconds to about 2 minutes, and in further embodiments from about 5 seconds to about 1 minute. A person skilled in the art will recognize that additional gelation time ranges within the stated ranges above are contemplated and are within the scope of the present invention.

The patch samples can also be tested for burst pressure, which is desirable to ensure that the sample will perform as desired in actual use. The burst pressure measurement is designed to provide standard test conditions for the patch to adhere to the hemorrhaging tissue. As previously mentioned, some patches can be formed using a compressed gelatin substrate, which provides a more flexible structure and/or a more uniform substrate surface while maintaining sufficient rigidity to resist buckling/distortion of the substrate during coating. The results presented in the examples below show that patches with compressed gelatin substrates exhibit nearly the same burst pressure. Experience has shown that patches with compressed gelatin substrates exhibit more uniform performance. As described below for the burst test description, the same sample can be used to evaluate swelling. The burst test can be evaluated in equipment designed to simulate hemorrhaging tissue applied to measurements in accordance with ASTM F2392-04 (2015). The ASTM protocol provides information regarding the surface of the test fixture, which is then adjusted for use with the porous plates of the test equipment. Although it is unlikely that a commercial version of this test device will ever be available, it would seem highly desirable for patch testing for clinical use. Accordingly, a comparable test device was constructed that took into account regulatory implications in its design, taking into account the ASTM protocols mentioned above, and is described in detail in the examples below.

For the test, a calibrated syringe pump was used, with a 60 ml syringe tube filled with saline and the pump speed set to 2 ml/min. The burst fixture is used with a cavity connected to the syringe pump and has a circular opening at the top of the cavity. A pressure sensor, such as a digital manometer, is also connected to the cavity to measure the pressure inside the cavity. To start the test, the cavity is filled using the syringe pump until it is almost full. For the gel test, the test block containing the patch sample is placed over the hole in the top of the fixture with the patch punch sample facing upward. Similarly, a hydrated patch pressed onto the test block can be used similarly, but using the patch after the gel test provides a uniformly prepared patch for the burst test. In this configuration, the hole in the sample holder is centered over the burst fixture cavity. The upper half of the fixture is then tightened over the test block, securing the sample holder with the hole associated with the cavity through the upper half of the fixture, exposing the sample from the top. When the test block is fixed to the upper fixture, the pressure measured by the manometer is expected to increase.

When the top of the fixture is secured in place, a pump is operated to pump water into the cavity, continuously increasing the pressure inside the cavity. The pump is operated until 1) liquid appears on the surface of the patch sample, 2) a popping sound is heard, and 3) the maximum pressure recorded on the manometer remains unchanged for 30 seconds. Once a certain condition is reached, the pump is stopped and the maximum pressure value obtained is recorded as the burst pressure, which is reported in millimeters of mercury (mmHg). For the patch samples described herein, the burst pressure can be at least about 10 mmHg, and in further embodiments at least about 15 mmHg, and in further embodiments at least about 50 mmHg, and in other embodiments from about 20 mmHg to about 1500 mmHg. A person skilled in the art will recognize that additional burst pressure ranges are contemplated within the above-specified ranges and are within the scope of the present invention.

Both the substrate and the precursor layer swell upon hydration. In principle, swelling can be assessed by a number of suitable methods, but in this specification, swelling is assessed by weight due to water retention. For embodiments based on compressed substrates, the swelling by weight may not vary significantly, so that the overall swelling estimate may be little changed compared to a similar patch assembled on an uncompressed substrate. The dry weight of the patch prior to testing may be used as an initial reference point. Ultimately, swelling may be assessed based on the results of incubation in aqueous solution, but prolonged incubation may result in degradation of the patch material. In principle, the swelling described herein is assessed after incubation in phosphate buffered saline at 37°C for a period of time sufficient for the swelling to stabilize, which may be approximately 24 hours for dense substrates and approximately 10 minutes for highly foamed gelatin sponges. The evaluation sample may be identical to the sample used for other property measurements, so that a consistent estimate of swelling can be obtained using the hydrated, unsoaked weight as a reference point. When assessing swelling directly from a dry sample, air can be squeezed out of the sample at an early stage of swelling, allowing for adequate measurements to be obtained without significant delay. In some embodiments, the sample after the burst test has been completed can be used to further assess swelling. After the burst test is complete, the sample can be carefully removed from the sample holder. The sample is then weighed to obtain the initial weight. The weighed sample is then placed in a 50 ml tube containing approximately 45 ml of phosphate buffered saline (PBS) and sealed. PBS is a standard buffer solution in medical and other biological applications, typically containing sodium chloride, potassium chloride, and phosphate. PBS is available from standard suppliers (Fisher Scientific, Sigma-Aldrich, etc.) and is listed in PubChem (https://pubchem.ncbi.nlm.nih.gov/compound/Phosphate-Buffered-Saline). The sealed tube is placed in a 37°C water bath. After 24 ± 2 hours, the tube is removed from the water bath. Then, the cultured sample is taken out, dried, and weighed. The swelling ratio value is determined by the following equation:

%inflation = 100 x (weight out - weight in)/weight in.

The "weight-in" value can be the dry weight, or a weight corresponding to an alternative reference point, such as the weight after burst testing. For the patches described herein, the swelling ratio (after 22 to 26 hours of incubation in PBS after burst testing) can be at least about 100%, and in further embodiments from about 135% to about 350%, and in other embodiments from about 150% to about 300%. A person skilled in the art will recognize that additional swelling ranges within the ranges specified above are contemplated and are within the scope of the present invention.

The substrate has a high swelling weight but may initially be porous and therefore have a low volume expansion. If the substrate is initially compressed relative to its initially formed dimensions due to the destroyed cells, some or most of the initial dimensions of the structure can be restored through swelling. Since the hydrogel precursor is initially dense, the volume change of the crosslinked hydrogel upon crosslinking and swelling is generally larger. Therefore, after hydration and swelling, the volume increase of the hydrogel layer may be more significant than the volume change of the substrate.

Another important feature is the persistence of the patch. In vitro measurements are possible for consistent measurements to mimic in vivo behavior. The persistence of the substrate and the associated crosslinked hydrogel layer can vary. The persistence behavior of the substrate can be evaluated by continuous swelling tests. Specifically, the sample placed in a tube containing PBS can be stored in a 37°C boiling water bath until the substrate of the patch sample is no longer visible. The time at which the substrate of the sample disappears is considered the end point of the substrate persistence time. Typically, the substrate disappears within 96 hours, in further embodiments within about 84 hours, and in further embodiments within about 15 minutes to about 72 hours. In some embodiments, it may be desirable for the substrate to disappear within about 48 hours. Those skilled in the art will recognize that additional degradation time ranges within the above-mentioned ranges are within the scope of the present invention. Typically, the hydrogel formed in situ lasts longer than the substrate.

Visualizer

If convenient, the biocompatible cross-linked hydrogel polymer may include a visualization agent to enhance visibility during a medical procedure, allowing rapid confirmation of the orientation of the patch relative to the surface to be placed on the wound. In principle, the substrate may have the visualization agent identical to, different from, or as an alternative to the hydrogel precursor layer. In an embodiment, there is a patch having a blue visualization agent only in the hydrogel precursor layer. As used herein, visualization may mean optical visualization (using color) or visualization using an imaging modality such as x-ray or ultrasound. Visualization agents are particularly useful in minimally invasive surgical (MIS, e.g., laparoscopic) procedures because, among other things, they provide enhanced visibility on a color monitor. Sometimes it is useful to add a colored visualization agent to the precursor melt prior to casting the hydrogel layer onto the substrate to provide color.

The visualization agent (optical) can be selected from a variety of non-toxic coloring materials suitable for use in medical implantable medical devices, such as FD&C BLUE dyes 1, 2, 3 and 6, indocyanine green, or coloring dyes commonly found in synthetic surgical sutures. In some embodiments, green or blue is preferred because of better visibility against blood or pink or white tissue backgrounds. The dye can be added in trace amounts to the molten mixture in the form of a dehydrated compound to form a dried hydrogel layer.

The selected colored agent may or may not be chemically bound to the hydrogel. Additional visualizing agents may include fluorescent (e.g., green or yellow fluorescein under visible light) compounds (e.g., fluorescein or eosin), X-ray contrast agents for visibility in X-ray imaging equipment (e.g., iodine compounds), ultrasound contrast agents (e.g., microbubbles), or MRI contrast agents (e.g., gadolinium-containing compounds). The biocompatible visualizing agents FD&C BLUE #1 and Fluoroscein-NHS may be particularly suitable for some applications. The visualizing agent may be the biologically active agent suspended or dissolved within the hydrogel matrix, or may be the material used to encapsulate the biologically active agent, if present.

As noted above, in some embodiments, a visually observable visualizer may be advantageously used. Humans can perceive colors in wavelengths from about 400 to 750 nm (R.K. Hobbie, Intermediate Physics for Medicine and Biology, 2nd Ed., pages 371-373). Blue is perceived when the eye primarily receives light with a wavelength of about 450 to 500 nm, and green is perceived from about 500 to 570 nm (Id.). Furthermore, since the eye only perceives red, green, or blue, combinations of these colors can be used to simulate other colors by conveying to the eye only the proportions of red, green, and blue that the human eye perceives as the desired color. As used herein, blue refers to a color that is perceived by the general human eye when stimulated by a wavelength of about 450 to 500 nm, and as used herein, green refers to a color that is perceived by the general human eye when stimulated by a wavelength of about 500 to 570 nm.

One or more visualizing agents may be present in the final electrophilic-nucleophilic precursor layer at a concentration suitable for visualization, for example from about 0.0001 mg/square centimeter (g/cm ² ) to about 0.5 g/cm ² , although higher concentrations up to the solubility limit of the visualizing agent may be used. In some applications, this concentration range has been found to impart the desired color to the hydrogel without interfering with the crosslinking time (as measured by the time for the reactive precursor species to gel). The visualizing agent is generally not covalently bound to the hydrogel. A person skilled in the art will recognize that additional concentration ranges of visualizing agents within the ranges specified above are contemplated and are within the scope of the present invention.

Visualization agents can aid in visualizing the interface between the patch and the underlying tissue. In some embodiments, dyes are incorporated into the patch by binding to electrophilic or nucleophilic end groups, allowing visualization that is directly correlated to persistence. In some cases, the dyes are fluorescent, allowing visualization only under special lighting conditions, and making the single-system gel invisible under normal visual conditions.

The user may view the hydrogel with the human eye using the visualizer, or with the aid of an imaging device that detects the visually observable visualizer, such as a video camera. A visually observable visualizer is a formulation that has a color that is detectable by the human eye. The property of providing an image to an X-ray or MRI device is not a sufficient property to establish its function as a visually observable visualizer. Alternative embodiments are visualizers that are generally invisible to the human eye, but are detectable at other wavelengths, such as infrared or ultraviolet, when used with an appropriate imaging device, such as a video camera. Similarly, the use of reflective materials, such as air bubbles, may allow for better imaging by ultrasound. Hydrogels containing visualizers for X-ray and/or ultrasound visualization are described in detail in U.S. Pat. No. 8,383,161 to Campbell et al., entitled "Radiopaque Covalently Crosslinked Hydrogel Particle Implants," which is incorporated herein by reference.

The radiopaque moiety can be introduced via a radiopaque precursor molecule or covalently bonded to the hydrogel functional group. For example, triiodobenzoic acid can be bonded to one arm of the precursor via an ester group. The total number of arms can be selected to achieve the desired crosslinking and radiopacity. CT number (also known as Hounsfield units or numbers) is a unit of measurement of visibility in indirect imaging techniques. A CT number of at least about 50 can be used, and in some embodiments the CT number can be from about 70 to about 2000.

Patch Formation Method and Storage

The method of making a patch comprises the steps of obtaining a substrate, applying a precursor layer, and packaging with a waterproof packaging material, as well as optionally one or more drying steps throughout the process. If the substrate is not a commercially available product, the method may further comprise the step of preparing the substrate. If the substrate is derived from a commercial product, processing may involve cutting a substrate of an appropriate size from a larger block of material or from a sheet of material. Some suppliers can provide sheets of gelatin substrate in the desired initial thickness. For commercial production, processing may result in a sheet of patch material having a hydrogel precursor layer, which may be cut to the desired size, if appropriate. The sizes may generally include a range of commercial sizes that a medical professional may select as appropriate, and as noted above, care should be taken to ensure that the patch can be cut to the desired size when used. Applying the precursor layer may involve delivering a molten mixture or solution coating with a non-aqueous precursor solution, and the layer deposition may optionally involve forming a sublayer. The moisture content can be reduced below the target amount for packaging, and since the material is generally hygroscopic, processing is carried out in a closed environment with low moisture vapor levels. The packaged patches are marked with a use-by date and time to reflect the appropriate shelf life and are distributed appropriately.

The substrate may be purchased in a usable form or processed from suitable raw materials. In the case of a gelatin substrate, it may be obtained in the form of a foamed sheet, which may then be subjected to calendering, coating and other further processing. The purchased material may be procured according to the product specifications, the desired patch properties being described above, and the substrate being suitably selected to meet these properties. Regardless of whether the material is procured or further processed to prepare the material for patch formation, the substrate may be further dried prior to adding the precursor layer. Drying may be accomplished by placing it in a drying oven, contacting it with a drying gas, separating it with a desiccant, a combination of these, or a variety of similar methods. Depending on the size of the substrate material, a suitable drying oven may be selected, and heating may be continued until the relative humidity falls below the target value. The heat treatment may be carried out under moderately mild conditions so that the properties of the material do not change undesirably. Suitable desiccants are commercially available, for example, zeolites, calcium chloride, calcium sulfate, etc.

In some embodiments based on gelatin sponge material as the substrate, the starting material can be purchased or manufactured. In either case, the material can be further processed by cutting to a specified thickness, if appropriate. Typically, a specific patch size cannot be cut until the hydrogel precursor layer is applied and compression performed, but some final processing can be performed after the size is cut. Commercial suppliers of gelatin sponge material include Ethicon (USA), Gelita (Germany), and Pfizer (Gelfoam®).

In some embodiments, the precursor layer may be formed using a solvent coating approach. The solution of the precursor should be non-aqueous to avoid situations where water must be removed and to avoid deprotonation of the amine. Nevertheless, the precursor should be dissolved in a solvent. Suitable solvents include, for example, aromatic liquids such as toluene, xylene, chlorobenzene, ethyl benzene, alkanes such as hexane, or aprotic solvents such as tetrahydrofuran, ethyl acetate, acetone, acetonitrile, dimethyl sulfoxide, or mixtures of two or more of these liquids. Typically, the concentration is selected as high as possible to accommodate process conditions such as viscosity, so that a uniform coating can be applied with a small amount of solvent. One skilled in the art can select the concentration based on the selected coating technique and the selected solvent. The solution may include other additives such as visualizing agents and biological/therapeutic agents. Suitable coating techniques include, for example, spray coating, jet printing, slot coating, screen printing, extrusion, etc. As is well known in the technical field, extrusion generally offers a different range of viscosities and solids contents than spray coating.

The solventless process has the advantage of avoiding waste disposal associated with solvent use. The flow temperature of polyethylene glycol (PEG)-based precursors is generally very low, less than 100°C, and is relatively small in dependence on molecular size. Some low molecular weight PEG-based precursors can remain liquid at room temperature and can be mixed with precursors that are solid at room temperature to form a solid mixture. Polyoxazolenes have a reasonably high flow temperature, typically about 150°C to 250°C, depending on the side chain and molecular weight. Therefore, mixtures of PEG-based precursors can be formed at relatively low temperatures and can be appropriately coated onto a substrate using an appropriate technique. The precursor layer can include other additives such as visualizing agents and biological/therapeutic agents. While other coating techniques can be used for melt deposition, slot die coating can be a convenient technique because it allows for a tunable coating thickness while maintaining the material at an appropriate temperature using suitable commercial equipment. The equipment can be selected to fit the desired substrate size, and the substrate can be conveniently supplied in sheet or roll form. Suitable commercial slot coating equipment includes, for example, FOM Technologies (Denmark), Yasui Seiki (Miriwek Film, Ink, IN, USA), and Coating Tech Slot Dies, Corp. (WI, USA).

FIGS. 2-4 illustrate various devices for forming a sealing patch (100) that can be used as a hemostatic patch. Referring to FIG. 2, a spray coating device (200) has a precursor mixture (202), which can be a molten mixture or an organic solvent mixture, within a vessel (204). The precursor mixture (202) can be a pure mixture of molten precursors. Alternatively, the precursor mixture (202) can be a molten mixture that includes one or more additional components to reduce viscosity. The additional components can include a solvent, such as, for example, an anhydrous organic solvent. The vessel (204) can mix and/or heat the precursor mixture (202) prior to delivery through a spray nozzle (205). A spray of the precursor mixture (206) is deposited onto a substrate (208) to form a sealing patch composition having a coating of mixed and unreacted precursor on the substrate (208). In some embodiments, the formed sealing patch composition is dried to remove the solvent and/or residual water. In some embodiments, the formed suture patch composition is cut into individual patches and stored in a humidity-controlled packaging material or container.

Referring to FIG. 3A, a slot die coating apparatus (300) has a molten mixture (302) within a vessel (304). The molten mixture (302) may be a pure mixture of precursors. Alternatively, the molten mixture (302) may have one or more additional components, such as an organic solvent to adjust viscosity. The vessel (304) may mix and/or heat the molten mixture (302) prior to passing the molten mixture (302) through the slot die (306) to form a film (308) on the substrate (310). The apparatus (300) may utilize additional equipment, such as filters, pumps, pulsation dampers, degassing devices, and/or flow controllers, between the vessel (304) and the slot die (306). Typically, the film (308) is a continuous liquid film. Suitable slot coaters are commercially available, and use of one commercial slot coater is described in the examples. The slot die (306) can have a variety of head sizes, viscosity grades, and stripe pattern options. The width of the film (308) can be selected based on the selection of the slot die (306). The width of the film and slot die can be selected to match the width of the desired product, or can be made wider and cut to size after coating, for example, cut to a width that is a multiple of the product width to form multiple products for each length of the coated substrate. The slot die (306) can be used to control the rate at which the molten mixture (302) is deposited onto the substrate (310), which is related to the thickness of the precursor on the substrate. Deposition of the coating with a slot die requires relative movement of the die and the substrate, which can include movement of the substrate, movement of the slot coater and die, or both. The apparatus (300) can similarly be used to coat solvent mixtures.

As previously mentioned, it may be desirable to deposit the liquid hydrogel precursor material, whether a melt or a non-aqueous solution, on and/or within the porous substrate under some compression. As illustrated in FIG. 3B , in connection with the slot die coating apparatus (350), a slot die (356) may be used to control the deposition rate of the molten mixture (302) and to inject the molten mixture (302) into the substrate (310). To effect the injection of the molten mixture (302), the slot die (356) and the substrate (310) move relative to each other, and the slot die (356) compresses the substrate (310) at the injection location. The force applied to the substrate (310) through the slot die (356), the depth to which the slot die (356) is compressed into the substrate (310), and/or the deposition rate may be adjusted to suit the cohesive hydrogel precursor structure that is formed. In some embodiments, the compression depth is from about 0.02 mm to 2 mm, in further embodiments from about 0.05 mm to about 1 mm, and in further embodiments from about 0.2 mm to about 0.8 mm. In other embodiments, the compression depth is from about 5% to about 30%, or from about 5% to about 15% of the substrate thickness prior to coating. Those skilled in the art will recognize that additional compression ranges for coating within the stated ranges are contemplated and are within the scope of the present invention. The porous substrate (310) may be somewhat elastic. Accordingly, with relatively light compression during coating, the substrate may recover to approximately its initial substrate thickness, as shown in FIG. 3B . Appropriate modifications to the slot die print head may be effective in applying the appropriate compression, but auxiliary structures may be used to achieve the appropriate compression adjacent the print head, and a calendar roller or similar device may also be used for this purpose.

In some embodiments, referring to FIG. 3a, the substrate (310) may be moved as indicated by the directional arrow (312) during deposition of the molten mixture (302), while the slot die (306) may be held in place. The speed at which the substrate moves along the directional arrow (312) and the parameters of the slot die (306) may be adjusted to vary the thickness of the film (308). If multiple layers are desired, the substrate may be moved again in the opposite direction to form a second layer, or may be moved again without coating and then moved forward along the directional arrow (312) to apply additional subsequent coating layers. Similar multiple coatings may be performed based on the embodiment of FIG. 3b. The substrate may be supplied as individual units that are coated, cooled and/or dried, and packaged. In other embodiments, the substrate may be provided as a larger sheet that is cut to size after coating, which may or may not be provided in roll form. The dried gelatin substrate is typically provided in a relatively rigid sheet form.

In another embodiment, the substrate (310) is stationary and the slot die (306) (FIG. 3A) or the slot die (356) (FIG. 3B) moves along the directional arrow (314) during deposition of the molten mixture (302). In a further embodiment, the substrate (310) is stationary and the slot die (306 or 356) moves along the direction indicated by the directional arrow (314) for a period of time or until a selected travel distance is reached and then moves in the reverse direction indicated by the directional arrow (316) for a period of time or until a selected travel distance is reached. The film (308) can be formed as a single deposited layer of the molten mixture (302) or as multiple deposited layers of the molten mixture (302). In some implementations, the film (308) is formed by alternately depositing the molten mixture (302) while moving the slot die (306 or 356) along the directional arrow (314) to form a first deposition layer, and then depositing the molten mixture (302) while moving the slot die (306 or 356) along the directional arrow (316) to form an additional deposition layer over the first deposition layer. The alternate deposition can be repeated a selected number of times to obtain a film (308) of a desired thickness.

In some embodiments, the film (308) is cooled to form a coating (309) as a solid on the substrate. In various applications, the coating (309) can be a continuous, solid hydrogel precursor network that is cohesive and at least partially integrated with the substrate (310). In some embodiments, the film (308) and/or the coating (309) are dried to remove solvent and/or residual water. The device (300) can be used to form a hydrogel precursor patch composition comprising the coating (309) on the substrate (310). In some embodiments, the structures formed using the hydrogel precursor patch composition on the substrate are cut into individual patches and stored in humidity-controlled packaging.

FIG. 4A is an exemplary embodiment of a roll slot die coating apparatus (400) having a substrate roll (402), wherein a substrate (404) is moved under a slot die (405) by a belt (401) moving at a selected speed. The belt (401) may be a convenient conveyor system and may be replaced with a series of rollers or the like. A vessel (406) contains a precursor mixture (408), which may be a molten mixture or an inert organic solvent solution. The precursor mixture (408) may be a pure mixture of the precursors. Alternatively, the precursor mixture (408) may have one or more additional components, such as a solvent to adjust the viscosity. The vessel (406) may mix and/or heat the precursor mixture (408) prior to conveying it through the slot die (405) to form a film (410) on the substrate (404). The coating apparatus (400) may utilize additional equipment such as filters, pumps, pulsation dampers, degassing devices, flow controllers, etc., between the vessel (406) and the slot die (405). In some implementations, the film (410) may be a continuous liquid film as deposited. The slot die (405) may have a variety of head sizes, viscosity grades, and stripe pattern options. The width of the film (410) may vary depending on the selection of the slot die (405). In some implementations, the film (410) has a width of from 1 cm to 10 cm. The slot die (405) may be used to control the deposition rate of the precursor mixture (408) onto the substrate (404), which affects the thickness of the film (410). In some implementations, the slot die (405) may be used to control the deposition rate of the precursor mixture (408) and to inject the precursor mixture (408) onto the substrate (404). To effect injection of the precursor mixture (408), the substrate (404) moves beneath the slot die (405), which compresses the substrate (404) at the injection location as illustrated in FIG. 3B. The force applied to the substrate (404) through the slot die (405), the depth to which the slot die (405) is compressed into the substrate (404), and/or the deposition rate can be adjusted to suit the cohesive hydrogel precursor network that is formed. In some embodiments, the compression depth is from about 0.02 mm to 2 mm, in further embodiments from about 0.05 mm to about 1 mm, in some embodiments from about 0.1 mm to about 0.8 mm, and in further embodiments from about 0.2 mm to about 0.75 mm. In other embodiments, the compression depth is from about 5% to about 30% or from about 5% to about 15% of the thickness of the substrate prior to coating. Those skilled in the art will recognize that additional compression ranges within the above-mentioned ranges are contemplated and are within the scope of the present invention. The speed of the belt (401) may also be adjusted to affect the thickness of the film (410). The film (410) may be formed from a single deposited layer of the precursor mixture (408) or multiple deposited layers of the precursor mixture (408).

In some embodiments, the film (410) is cooled to form a coating (412). Typically, the coating (412) is a cohesive solid coating, although portions of the substrate may be left uncoated if desired, and the coating may crack. The film (410) and/or the coating (412) may be dried to remove solvent and/or residue. The coating device (400) forms a hydrogel precursor patch sheet comprising the coating (412) on the substrate (404). In some embodiments, a cutting unit (414) is used to cut the hemostatic patch sheet into patches (416). The patches (416) may then be placed into a waterproof package (418).

FIG. 4b is an outline of a process (430) for improving the properties of a medical patch using a two-step compression process. In the process (430), the substrate calendering (434) is the first compression step. Following the step (438) of applying a precursor to the substrate as a melt, the second compression step, coating substrate calendering (442), is performed. Of course, other process steps, such as additional calendering steps, cutting steps, drying, sterilization, packaging, and other appropriate process steps, may be assembled around the steps specified in FIG. 4b.

The methods and structures described herein improve the properties of medical patches by contributing to the manufacture of a substrate for receiving a precursor composition. The substrate calendering step (434) can facilitate more consistent application of the precursor to the substrate as a melt (438), can generally be used for non-aqueous solution coatings, and can maintain a relatively rigid substrate for performing the coating. In general, the substrate calendering step (434) can reduce thickness variability of the substrate, and may cause some disruption of the cell structure of the substrate. The slight disruption can improve penetration of the precursor into the substrate while maintaining adequate rigidity of the substrate, and can, for example, prevent warping or distortion of the substrate during and/or after the step of applying the precursor as a melt onto the substrate. In some embodiments, the substrate calendering step (434) can reduce the thickness of the substrate by up to 65%. In other embodiments, the substrate calendering (434) can reduce the thickness of the substrate by 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40%. In some embodiments, the compression of the substrate induced by the substrate calendering (434) is at least partially reversible. In some embodiments, the thickness of the substrate partially recovers from the fully compressed thickness after the substrate calendering (434). In some embodiments, the substrate thickness recovery can ultimately result in a final thickness reduction that is 75%, 60%, 50%, 40%, or 25% of the initial thickness reduction. Following the substrate calendering step (434), the precursor is applied to the substrate as a melt (438), FIG. 4A illustrates one embodiment of this step. As previously mentioned, the compression during the hydrogel precursor deposition can be relatively mild, and there can be little or no thickness reduction of the substrate after the hydrogel precursor coating is formed. The second compression step is the step of forming the coating substrate calendering (442), which is performed after the precursor coating has been applied to the substrate and solidified. The precursor layer can be exposed to the surrounding environment or, optionally, can be solidified relatively quickly through a cooling step. The coating substrate calendering (442) can impart enhanced flexibility and hemostatic performance to the coating substrate. This can be accomplished, for example, by introducing appropriately induced cracks into the precursor coating and introducing additional cracks into the substrate. In general, the coating substrate calendering (442) can cause relatively mild or relatively significant destruction of the precursor coating. In some embodiments, the destruction comprises microscopic cracks of varying width, length, and density across the surface, which can be referred to as fractured, reflecting the variation across the surface. Some of the destruction can be surface destruction, while other destruction can have a depth similar to the depth at which the precursor penetrates into the substrate. In some embodiments, the coating substrate calendering (442) can reduce the thickness of the coating substrate by up to 65%. In other embodiments, the coating substrate calendering (442) can reduce the thickness of the coating substrate by 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40%. A person skilled in the art will recognize that additional ranges of dimensional variations within the stated ranges are contemplated and are within the scope of the present invention.

The substrate calendering step (434) and/or the coating substrate calendering step (442) can change the size, shape and structure of the cells/pores within the substrate. Typically, the process (430) collapses the pores and destroys the support surrounding the pores. Without wishing to be bound by theory, it is believed that the change in porosity of the substrate upon compression is associated with improved performance of the flexible medical patch. In some embodiments, the process (430) imparts significant flexibility and other performance improvements to the coating substrate.

FIG. 4c is a diagram illustrating a process flow (450) of a substrate through a process device for making a patch (487) from a gelatin sheet (451). The process device may or may not be configured for continuous processing, with a substrate sheet inserted at one end and a patch removed at the other end. To provide a cooling step, a solidification step, or similar steps, components of the process device may be correspondingly configured to allow for such steps, which may take more time than the active processing steps. Some process components may be configured to continuously perform a subset of the process steps, as convenient. Of course, an overall stable process speed can be achieved, so that the process equipment can be used efficiently.

In some embodiments, the gelatin sheet (451) has a thickness of from about 0.5 mm to about 1.5 cm. In the process flow (450), the gelatin sheet (451) is subjected to thermal crosslinking (452) in an oven (453) or other suitable heating device, which may also optionally include control components. The oven (453) may be any convenient oven capable of accommodating one or more gelatin sheets (451). Typically, the gelatin sheet (451) may be of any convenient width and length. The thermal crosslinking (452) may be performed at a constant temperature for a selected time, or may be performed using a selected heating profile. The oven (453) may optionally be integrated with a heater conveyor system (not shown) that can move the gelatin sheet (451) at a selected speed to achieve a target heating time or other target heating profile, which may or may not interface directly with other process devices.

Referring to FIG. 4c, following thermal crosslinking (452), the crosslinked substrate (454) may undergo substrate compression (455). In some embodiments, the crosslinked substrate (454) is at room temperature prior to substrate compression (455). In some embodiments, the crosslinked substrate (454) has a thickness of from about 0.5 mm to about 1.5 cm. Substrate compression (455) is performed using calendar rollers (456 and 457). The calendar rollers (456 and 457) are positioned at a selected distance from each other to form a gap (458). Typically, the gap (458) is less than a thickness of the crosslinked substrate (454). In some embodiments, the gap (458) is no more than 65% of the thickness of the crosslinked substrate (454). In other embodiments, the gap (458) is from 5% to 65%, from 10% to 50%, from 15% to 40%, or from 20% to 40% of the thickness of the crosslinked substrate (454). The calendar rollers (456 and/or 457) may or may not be heated. Compared to the crosslinked substrate (454), the compressed substrate (459) has a disrupted cell structure instead of an intact cell structure. Typically, the compressed substrate (459) is thinner and has a more consistent thickness than the crosslinked substrate (454). In some embodiments, the compressed substrate (459) has a thickness of from about 0.25 mm to about 1 cm, from about 0.5 mm to about 7 mm, from about 3 mm to about 6 mm. In some embodiments, the substrate compression (455) is integrated with a conveyor system (460) having a belt (461). The conveyor system (460) may be a convenient conveyor system, and the belt (461) may be replaced with a series of rollers or the like. In some embodiments, the calendar roller (457) may be part of the conveyor system (460). Those skilled in the art will recognize that additional ranges of thicknesses and percentages are contemplated within the stated ranges and are within the scope of the present invention.

Next, referring to FIG. 4c, the compressed substrate (459) is subjected to a coating (462) using a coating device (491). The coating device (491) is similar to the roll slot die coating device (400) of FIG. 4a, except that it is not configured for a roll-based substrate. A vessel (463) contains a precursor mixture (464), which may be a molten mixture or an inert organic solvent solution. The precursor mixture (464) may be a pure mixture of molten precursors. Alternatively, the precursor mixture (464) may have one or more additional components to adjust the viscosity, such as a non-aqueous solvent. The vessel (463) may mix and/or heat the precursor mixture (464) prior to conveying the precursor mixture (464) through the slot die (465) to form a film (466) on the compressed substrate (467). The coating (462) may utilize additional equipment such as filters, pumps, pulsation dampers, degassing devices, flow controllers, etc., between the vessel (463) and the slot die (465). In some embodiments, the film (466) may be a continuous liquid film as deposited. The slot die (465) may have a variety of head sizes, viscosity grades, and stripe pattern options. Suitable slot die coaters are commercially available. The width of the film (466) may vary depending on the selection of the slot die (465), and generally the width may be any reasonable value. In some embodiments, the film (466) has a width of from 1 cm to 100 cm, or in some embodiments from about 2 cm to about 20 cm. The slot die (465) may be used to control the deposition rate of the precursor mixture (464) onto the press substrate (467), which affects the thickness of the film (466). The speed of the belt (461) may also be adjusted to affect the thickness of the film (466). The film (466) may be formed as a single deposited layer of the precursor mixture (464) or as multiple deposited layers of the precursor mixture (464). In some embodiments, the film (466) is formed as a cohesive hydrogel precursor network. In some embodiments, the film (466) is formed by injecting the precursor mixture (464) into the compression substrate (467) while further compressing the compression substrate (467) at the injection location. In some embodiments, the film (466) is cooled to form the coating (468). Typically, the coating (468) is a continuous solid coating, although portions of the substrate may be left uncoated if desired. The film (466) and/or the coating (468) may be dried to remove solvent and/or residue. In some embodiments, the coating (468) has a thickness within the ranges described above and is capable of penetrating into the compression substrate. In some embodiments, the coating (468) is part of a cohesive hydrogel precursor structure that at least partially penetrates into the compression substrate (467). In some embodiments, the coating (468) is part of a cohesive hydrogel precursor structure having a surface that matches a surface of the compression substrate (467). In some embodiments, the cutting unit (469) is used to remove the front portion (470). Removing the front portion (470) can provide a more consistent coating on the patch (487).

Next, the coating substrate (471) having the coating (472) and the compression substrate (473) undergoes coating substrate compression (476) to form a compression coating substrate (477). The coating substrate compression (476) can be performed using calendar rollers (478 and 480). As shown in FIG. 4d, the calendar rollers (478 and 480) are positioned at a selected distance from each other to form a gap (481). Typically, the gap (481) is smaller than the thickness of the coating substrate (471). In some implementations, the gap (481) cannot exceed 75% of the thickness of the coating substrate (471). In other implementations, the gap (481) is 15% to 70%, 20% to 65%, 22% to 62%, or 30% to 60% of the thickness of the coating substrate (471). In some embodiments, the compression coating substrate (477) has a thickness of from about 0.3 mm to about 1 cm, and in other embodiments from about 0.5 mm to about 5 mm. The calendar rollers (478 and/or 480) may or may not be heated. The compression coating substrate (477) has a fractured coating (482) and a compression substrate (483). Typically, the compression coating substrate (477) is thinner and more flexible than the coating substrate (471). In some embodiments, the fractured coating (482) has microfractures of varying widths, lengths, and depths essentially across the entire surface, thereby representing a fractured surface. In some embodiments, the fractured coating (482) has a relatively constant ratio of fractured surface area to total surface area over most of the surface area. In some embodiments, the edges of the fractured coating (482) are different than other areas of the fractured coating (482). In some embodiments, the destroyed coating (482) has a thickness of from about 0.1 mm to about 8 mm, from about 0.15 mm to about 7 mm, from about 0.2 mm to about 5.5 mm, from about 0.25 mm to about 5 mm, from about 0.35 mm to about 4.5 mm, and in some embodiments from about 0.5 mm to about 4 mm. In some embodiments, the compressed substrate (483) has a thickness of from about 0.1 mm to about 9 mm, from about 0.15 mm to about 8 mm, from about 0.25 mm to about 6 mm, from about 0.5 mm to about 5.5 mm, from about 0.75 mm to about 5 mm, and from about 1 mm to about 4 mm. In some implementations, the coating substrate press (476) is integrated with a conveyor system (460) having a belt (461), which also transports the substrate through the substrate press (455). In some implementations, the calendar roller (480) may be part of the conveyor system (460).

Next, the flexible hemostatic patch sheet (486) may be cut (484). During the cutting (484), a cutting unit (485) is used to cut the flexible hemostatic patch sheet (486) into patches (487), which may include cutting based on length and/or width. During the optional packaging (488), the patch (487) is placed in a waterproof packaging (490).

Processing may be performed in a controlled atmosphere, such as dry nitrogen or other inert gas. After the patch is formed, it may be packaged in moisture-proof packaging, such as a polymer and/or foil pouch, under a dry inert gas. The patch may be further dried, for example, by heating to a temperature of from 40° C. to 90° C. The package may contain a desiccant to help maintain dryness. For example, the patch may be sterilized using radiation after packaging. Sterilization may be performed under conditions that do not induce significant crosslinking. The package is appropriately labeled according to the instructions for medical use and includes an expiration date.

The patches are generally stored in waterproof packaging. In some embodiments, the patches are heat sealed in a foil pouch. To extend the shelf life, it may be desirable to refrigerate the patches. Typically, the patches can be stored at a temperature of up to about 5° C., or at standard refrigerator temperatures, perhaps in the range of 1° C. to 7° C., although lower temperatures may be used if desired. For short-term storage, the patches can be stored at room temperature. At refrigerated temperatures, the patches can be stored for at least 2 months, in further embodiments at least 1 year, in further embodiments from 3 months to 3 years, and in some embodiments from 6 months to 2.5 years. Those skilled in the art will recognize that additional storage temperature and time ranges are contemplated within the above stated ranges and are within the scope of the present invention. Patches that have exceeded their shelf life can be identified as having insufficient adhesion due to premature cross-linking or premature hydrolysis that removes the electrophilic groups for cross-linking.

Biologicals and Drugs

The patch may optionally include a biological agent in addition to the visualizing agent. The optional biological agent or drug may be, for example, an agent that promotes blood clotting and/or healing. Thrombin may also be added to the patch, which provides good hemostatic function without the complex process of adding blood products to the patch composition. Using a rapidly absorbing patch material allows the patch to disintegrate before significant concerns about adhesion formation or microbial contamination arise. However, an antimicrobial agent may be added if desired. In further embodiments, the therapeutic agent may include an analgesic, anesthetic, a steroid, an antibiotic, a steroid, an anti-infective, an anti-inflammatory, a non-steroidal anti-inflammatory, an anti-proliferative agent, or a combination thereof. This approach can be effectively used for local drug delivery because the patch provides local adhesion and acts as a reservoir for the added drug or biological agent.

Uses and medical indications of the patch

The medical patch described herein is particularly useful for use as a hemostatic patch. A hemostatic patch is intended to stop bleeding by applying pressure to a site of minimal, mild, or moderate bleeding. The patch may or may not contain a therapeutic agent, such as a compound that promotes clotting, and in the examples, effective hemostasis has been demonstrated without a biologically active agent. The patch may be used more generally in contact with exposed tissue, without necessarily being used to control severe bleeding, and may also be used in surgical suture applications. The cross-linking of the patch is activated upon contact with biological fluids. With appropriate substrates and thicknesses, the patch can remain relatively flexible and conformable even in a dry state, a feature that may be utilized in certain applications.

In general, the patch can be delivered directly to the wound site, such as in open surgery. In an alternative embodiment, the patch can be used in laparoscopic surgery because it is flexible enough to be delivered through a trocar. The patch can be conveniently applied over the wound with the hydrogel precursor layer facing the wound, but alternatively, the patch can be folded and inserted into the wound, for example with the hydrogel precursor side facing outward, such that the patch fills the wound.

To provide additional patch delivery options, FIG. 13a shows a loosely accordion folded patch (750). FIG. 13b illustrates a process (800) for inserting an accordion folded patch (801) into a cannula (803) via forceps (805). The process (800) can be used to direct the accordion folded patch (801) to a treatment site. FIG. 13c illustrates an embodiment where a patch (806) is folded into an accordion shape and then widthwise folded. FIG. 13d illustrates a process (810) for inserting an accordion folded and widthwise folded patch (812) into a cannula (814) via forceps (816). The process (810) can be used to direct the accordion folded and widthwise folded patch (812) to a treatment site. In some implementations, the process (800/810) can be used to preload the cannula (803/814) for future use. In some implementations, the process (800/810) can be used to preload the cannula (803/814) for packaging as a "pre-loaded" patch. In some implementations, the process (800/810) can be used with a tubular applicator instead of the cannula (803/814). Both the patch (750) and the patch (806) provide a more compact shape than a flat patch, which may be convenient for certain applications, such as laparoscopic surgery.

FIG. 14 is an example of patch delivery for use in a laparoscopic procedure (820), wherein an accordion-folded patch (824) is inserted into a laparoscopic site (831) through a cannula (826) using forceps (828). The forceps (830) are inserted into the laparoscopic site (831) through the cannula (834). The forceps (830) may assist in guiding the accordion-folded patch (824) to a treatment site (838). In some embodiments, the treatment site (838) may be a wound site or a surgical site for suture. In some embodiments, the accordion-folded patch (824) may be used to provide hemostasis in a laparoscopic procedure (820). In some embodiments, the coating of the accordion-folded patch (824) may crack at the fold lines. In some embodiments, a crack in the coating of the accordion-folded patch (824) may extend to the substrate surface. Typically, the accordion-folded patch (824) can heal the crack on its own by swelling when hydrated by body fluids at the treatment site.

The hemostatic patch may be ground or finely divided as desired and used alone or as a filler in combination with other patches or parts of patches. The finely divided patch formulations described above or similar granular compositions may be dispensed through a cannula attached to a bellows type device. Such formulations may be useful for sealing or controlling extensive bleeding in tissues.

In some embodiments, the patch may be applied to the tissue immediately prior to application to initiate hydration by wetting it with a sterile aqueous solution, such as saline or water for injection. Typically, the patch is applied to the tissue with a sterile gauze pad or similar pad to facilitate the application process, wherein the gauze pad is defined herein as a pad of non-adhesive absorbent material. The gauze pad is used to apply approximately even pressure for a period of time to ensure good adhesion of the patch. The selected time is typically at least about 5 seconds, in further embodiments at least about 8 seconds, in some embodiments from about 10 seconds to about 4 minutes, and in other embodiments from about 12 seconds to about 2 minutes. Those skilled in the art will recognize that additional time ranges are contemplated within the above-described ranges and are within the scope of the present invention. Placing the patch may include using a single patch on the bleeding defect or placing multiple medical patches. The additional medical patches may overlap at least a portion of the first medical patch.

In a wound, bleeding can be stopped by using a patch through a process called hemostasis. Hemostasis involves clotting until bleeding stops and can be considered the first step in wound healing. After hemostasis, no more blood is released from the wound. Using the patches described herein, hemostasis can generally be achieved within about 5 minutes, and in some embodiments within 3 minutes or less. Those skilled in the art will recognize that additional hemostasis time ranges are contemplated within the above-mentioned ranges and are within the scope of the present invention.

A specific application of interest is the application of the patch to or within a wound or blood vessel of an organ. While hemostasis is generally associated with all wound healing, the degree of bleeding can vary considerably. The patches described herein can be used regardless of the degree of bleeding, but as demonstrated in the examples, can be effective even with severe bleeding. In the context of a surgical procedure, the patches can be used for placement in orthopedic applications such as blood vessels, the liver, intestines, uterus, pancreas, other organs, bone and connective tissue, or generally in procedures involving all surgical wounds as well as traumatic wounds. In some embodiments, the patches can be placed along the skin to close a wound on the surface of a patient or to close a surgical intervention.

In general, any wound of any tissue can be effectively covered with the patches described herein, but the patches may be particularly effective in covering wounds of organs that are prone to severe bleeding. Suitable organs include, for example, bones, glands, digestive organs, lung organs, urinary organs, reproductive organs, blood vessels, interfaces with natural or synthetic grafts, or combinations thereof. In some embodiments, the organ is an artery or vein, and the organ may generally be natural, grafted, or a combination thereof. In particular, the patches may be applied to a bleeding defect. The bleeding defect may be, for example, a suture line, a puncture wound, a gunshot wound, a hole, a dent, a biopsy punch hole, a graft interface, or a combination thereof. Placing the patch may comprise placing one or more medical patches on a bleeding defect that is not flat in shape, which is often determined by the shape of the organ. Placing the patch may comprise wrapping one or more medical patches around the organ. The extent of organ bleeding may be assessed based on the Spot Grade bleeding score or other validated bleeding scale.

In some embodiments, the patch itself may be packaged in a pre-folded form, as illustrated in FIGS. 13A and 13C , or packaged in a "pre-loaded" form that can be deployed from a tubular applicator to squeeze the patch near the treatment site using a mechanism such as a mandrel or plunger. Pre-loading the patch is useful for laparoscopic applications where it is inserted through a narrow tubular opening, allowing the patch to be further advanced to the site of hemostasis upon introduction via the laparoscopic manipulator, which may also apply pressure to secure the patch to the wound. In other embodiments, the pre-loaded configuration places the packaged patch or cylindrical patch into a defect site, such as a gunshot or stab wound, where hemostasis due to the flat substrate topography is less than ideal. In further embodiments, the pre-formed patch-mandrel relationship may be configured to deliver a geometry that is less than ideal for hemostasis using a flat patch, with the mandrel surface having a desired shape to conform the patch to the wound.

One application envisioned is a conical pre-shaped patch attached to a conical mandrel to create hemostasis following a loop electrosurgical excision procedure (LEEP) of cervical tissue. In this situation, the shape of the mandrel and the pre-shaped patch fill the irregular conical depression left by the LEEP procedure, and the mandrel can be removed once the patch is attached and hemostasis is achieved. Figures 12A and 12B illustrate one embodiment of such an application. Figure 12A shows a conical hemostatic patch (700) positioned on a cervix (704) using a conical mandrel (702). Figure 12B shows a hemostatic patch (710) placed within the cervix (704). The left inset shows the conical pulley (702) applying pressure to the conical hemostatic patch within the cervix (704). The right illustration shows the cone-shaped mandrel (702) removed and the hemostatic patch (710) attached to the irregular cone-shaped recessed portion of cervical tissue. For embodiments of this and similar forms, the patch can be heated to soften the precursor layer into the shape of a mandrel, or otherwise formed into a desired shape. When cooled on the mandrel, the shape can be essentially maintained when placed.

In further embodiments, the patch is softened and conformed to the shape by processing or pre-wetting, and can be applied to additional gynecological applications. In certain embodiments, the adaptive patch is used to stop bleeding during hysterectomy after cesarean section. Additionally, the softened patch can be applied along the cervix to stop postpartum hemorrhage. Postpartum hemorrhage is a very concerning condition in which the mother experiences rapid blood loss, leading to hypotension, shock, and eventually death. In some cases, after therapeutic intervention and manual pressure to stop the bleeding, a softened patch that can be delivered through the vagina/cervix can be delivered to conform to the irregular uterine surface, thereby avoiding the need for more extreme outcomes such as surgical intervention, hysterectomy, or death. Ideally, the patch should achieve rapid hemostasis within 1-2 minutes and then be rapidly absorbed, thereby reducing interference with further medical diagnosis. Multiple patches can be applied until hemostasis is achieved.

In some embodiments, the patch is soaked immediately prior to delivery to the application site, but placement of the patch or patches may be performed without pre-wetting one or more of the medical patches. In some embodiments, the step of placing one or more patches comprises wetting one or more of the medical patches with unbuffered water or unbuffered saline prior to and/or after placement. Whether or not the patch is pre-wetted, the patch absorbs moisture relatively quickly. As the precursor crosslinks to form a hydrogel, the precursor layer becomes adhesive to the application site. Typically, the precursor layer hydrates and adheres to the organ or other tissue within about 2 minutes.

Ocular applications may include patches having a substrate that prevents the reactive precursor from adhering to the applicator or user while being applied to the wet ocular surface. In certain embodiments, the substrate is rapidly soluble or removable, so that it remains in place just long enough to prevent adhesion during application. In other embodiments, the substrate is non-absorbable, continues to provide structural support to the mixed molten precursor, and is removed after application of the precursor. Ocular applications of pre-mixed precursor melts containing therapeutic agents for treating ocular surface conditions (e.g., post-surgical pain control) and/or treating the anterior chamber of the eye are contemplated. In such embodiments, a releasable backing is used to apply the molten precursor and therapeutic agent to the fornix of the eye, and then is removed after crosslinking has begun. In some cases, the molten mixture of precursors may be less compatible with the substrate, resulting in poor adhesion to the substrate during application. In other circumstances, the molten precursor is pre-formed, cut to a shape for insertion, and the substrate backing is added later or prior to application. When adding the substrate after the unreacted mixture has been formed, a binder, such as a low Mw PEG liquid, can be used to enhance the attachment of the molten blended precursor to the substrate during storage or immediately prior to application. One embodiment may include a molten precursor wafer attached to a disposable applicator substrate that can be disposed of after administration to the eye canal in a patient.

In these embodiments, multiple therapeutics can be administered in sufficiently large doses over potentially shorter periods of time by self-administration by the patient. The higher therapeutic dose allows for a wider range of drug substances to be used with lower potency. High potency candidates are a limitation for ocular implants that are limited to small-volume applications such as punctal plugs, anterior chamber, posterior chamber, and suprachoroidal injections. For example, the use of NSAIDs or bupicaine for topical fornix delivery instead of highly potent corticosteroids, which can have potentially negative effects such as increased intraocular pressure with long-term use, is an example. In these embodiments, the need for potent therapeutics alone is eliminated, allowing ocular applications in the anterior chamber of the eye to treat pain, inflammation, dry eye, infections, etc.

In a surgical context, the patch will generally provide the desired burst strength, although sutures may also be applied, such as dissolvable sutures, if desired. In the case of a degradable patch, the applied patch is sutured inside the patient so that it can be safely degraded at an appropriate time, thereby providing hemostatic stabilization. Typically, no further intervention is required with the patch, but in rare instances, supplemental treatment of the wound may be provided. When used in vivo, the patch will generally degrade and be eliminated from the body, typically being completely eliminated via the kidneys within 28 days, in further embodiments within 21 days, and in other embodiments within 7 to 14 days. Those skilled in the art will recognize that additional time periods are contemplated within the above-mentioned ranges and are within the scope of the present invention. In an alternative embodiment, the patch may be designed such that the hydrogel is essentially non-absorbable, allowing for extended durations.

FIG. 5 is a drawing of a hemostatic patch (501) wrapped around a tubular organ (504). In some embodiments, the tubular organ (504) is an artery or a vein. The wrapped hemostatic patch (501) can have a tail (506) formed by connecting two ends of the hemostatic patch (501). The hemostatic patch (501) can be dry prior to wrapping, or can be pre-wetted. Examples 5 and 6 illustrate a method of wrapping a suture line around a femoral artery using a hemostatic patch (501). Example 6 illustrates wrapping a hemostatic patch (501) using a double layer of wet gauze and a hemostatic patch (501). As illustrated in Example 5, the hemostatic patch can be placed on a tubular organ and/or tubular graft without wrapping. Example 6 illustrates an unwrapping process for establishing hemostasis in a cavity-type bone defect using a disc-shaped hemostatic patch.

Figure 6 is a drawing of a hemostatic patch (512) placed on a non-vascular organ (514). Examples 3 and 4 demonstrate methods of placing a hemostatic patch (512) on a liver defect site including concave and convex defect surfaces. Figure 7 is a drawing of a hemostatic patch (518) placed on skin (520).

FIGS. 8A to 8D illustrate the mechanism of action of the hemostatic patch. FIG. 8A shows a hemostatic defect (600) in a tissue (604) through which blood (606) flows. FIG. 8B shows a hemostatic patch (607) placed in the tissue (604). The hemostatic patch (607) is placed such that the substrate (608) faces away from the hemostatic defect (600) and the molten mixture layer (610) faces the hemostatic defect (600). Blood (612) from the hemostatic defect (600) seeps into the hemostatic patch (607), causing precursors within the molten mixture layer (610) to dissolve and interact to form a crosslinked hydrogel layer (616) ( FIG. 8C ). In some embodiments, the molten mixture layer (610) reacts to form a crosslinked hydrogel layer (616) within 30 seconds of placing the hemostatic patch (607) on the bleeding defect (600). FIG. 8c also shows that the substrate (618) is suitable for causing the hemostatic patch (620) to adhere to the tissue (622) and seal the bleeding defect (600) to create a hemostatic defect (624). FIG. 8d shows healed tissue (626) into which the hemostatic patch (620) has been absorbed.

Example

Examples 1 to 8 relate to the general formation of hydrogel precursor layers and the demonstration of hemostatic efficacy in several model systems. Example 9 relates to the evaluation of the properties of the compression substrate, the formation of patches, and the properties of the resulting patches.

Example 1: Preparation of hemostatic patch samples

In this example, preparation of a hemostatic patch sample is described.

Hemostatic patch samples were prepared by melt coating a dry mixture of two hydrogel precursors onto a porcine gelatin substrate. Various gelatin/collagen substrates were prepared as shown in Table 1. Each substrate was crosslinked, with light crosslinking meaning less than about 20% crosslinking and high crosslinking meaning greater than about 20% crosslinking. Substrates A, B, and D were characterized by small (micron-sized or smaller) pores and greater than 80% porosity as measured by mercury penetration porosimetry. Each substrate was oven-dried at 35°C in ambient air for 18 hours or until the relative humidity of the oven was less than 5% to prepare the coating. The thickness of the gelatin substrate after drying was approximately the same as before drying. In each patch sample, the first hydrogel precursor was a polyethylene glycol-based precursor with an eight-arm molecular weight of 15,000 Da and succinimidyl glutarate (SG)-functionalized end groups (8A15k PEG SG, Jenkemusa). The second hydrogel precursor was a polyethylene glycol-based precursor with an eight-arm molecular weight of 20,000 Da and HCl-chlorinated amine-functionalized end groups (8A20k PEG amine-HCl, Jenkemusa). The first and second precursors were measured in powder form and then melt-mixed in a glove box with a trace amount of FD&C Blue#1 on a heated roller system at a temperature greater than 45°C. The melted precursor mixture was delivered to a liquid dispensing system (Vulcan™ Jet Dispenser, Nordson). A single coating layer of the molten mixture was applied to the dry gelatin substrate at a width of 0.5 mm per pass and a line speed of 50 mm/sec under inert gas conditions until the total width of the coating was approximately 20 cm. The thickness of the coating was approximately 0.25 mm. The mixed precursor coating substrate was allowed to solidify at room temperature under inert gas conditions. The resulting coating substrate measured a thickness of approximately 1.25 mm. The coating substrate was cut into individual hemostatic patches measuring approximately 2x4 cm and packaged in foil containers or disposable pouches, both of which were designed to maintain an initial relative humidity of the inert gas within the container of approximately 20 ppm or less. Suitable commercial medical packaging materials include Amcor PerfecFlex 35772-E or Paxxus Symphony 26-1010. The patches were sterilized after packaging. The mixed precursor coating side (the “active side”) of each patch was identified by a blue color, while the back of the substrate on the opposite side of each patch was free of blue color.

Description type characteristic Thickness of substrate A Non-glossy (open cell), foamed gelatin/collagen with small pore size, low cross-linking 1 mm B Two-layer substrate A (non-glossy, foamed gelatin/collagen with small pore size, low cross-linking) 2 mm C Non-foaming gelatin/collagen, low cross-linking 1 mm D Non-glossy, foamed gelatin/collagen with small pore size, highly cross-linked 1 mm

Example 2: In vitro testing of hemostatic patch samples and substrates

In this example, the gelation time, burst pressure, swelling and durability of a series of hemostatic patches prepared according to Example 1 were evaluated. The swelling and durability of the substrate were also evaluated in this example.

Part A. Test Samples and Test Procedure. In this study, hemostatic test patches were prepared using substrate type A (“Test Patch A”) according to Example 1. Separately, (uncoated) samples of substrate A and substrate D with low and high crosslinking were also tested. Individual samples for testing were cut from a single piece of test patch A or a single piece of substrate A or substrate D. The test method used in this example is described in the “Hydrogel and Patch Characterization” section above.

Part B. Description Test.

The swelling of the sample of substrate A was evaluated. The sample of substrate A was weighed and then immersed in a phosphate buffered saline (PBS) solution maintained at 37°C for a selected time. Tables 2 to 4 show the swelling ratio of the sample after 30 seconds, 1 minute, and 2 minutes, respectively. The swelling ratios of the sample after 30 seconds, 1 minute, and 2 minutes were 814 wt%, 973 wt%, and 1053 wt% on average, respectively. The results of the study indicate that a biocompatible substrate can be manufactured to have a high swelling rate and a high degree of swelling in 30 seconds.

Sample mass, g Inflation in 30 seconds 1 0.0065 835 % 2 0.0069 955 % 3 0.0068 954 % 4 0.0065 717 % 5 0.0065 837 % 6 0.0067 673 % 7 0.007 807 % 8 0.0071 728 % 9 0.0073 896 % 10 0.0069 735 % average 0.06237 814 %

Sample mass, g Expansion in 1 minute 1 0.0071 887 % 2 0.007 1017 % 3 0.0073 892 % 4 0.0073 1049 % 5 0.0066 1018 % average 0.07568 973%

Sample mass, g Expansion in 2 minutes 1 0.0068 1103% 2 0.0069 1077 % 3 0.0068 1000 % 4 0.0072 993% 5 0.0074 1092 % average 0.08094 1053 %

Samples of Substrates A and D were evaluated for persistence in PBS solution. The samples were immersed in PBS solution maintained at 37°C. The samples were visually evaluated after 67 hours (2.8 days), 96 hours (4.0 days), and 114 hours (4.8 days). As shown in Table 5, each of the Substrate A samples (Samples 1 to 10) was observed to persist partially after 67 hours. Samples 1 to 10 were not visible at 96 hours, indicating that the persistence of Substrate A ranged from about 2.8 days to about 4 days. Each of the Substrate A samples (Samples 11 to 15) was observed to persist after 114 hours.

The results demonstrate that substrate sustainability in a simulated in vivo environment can be well controlled through substrate processing. The results also demonstrate that biocompatible, absorbent substrates can be fabricated with high percentage and overall water uptake, and that these highly absorbent substrates can be designed to persist over a controlled period of time.

Sample Description/Crosslinking Shown after 67 hours Shown after 96 hours Shown after 114 hours 1 A/Low Partial N -- 2 A/Low Partial N -- 3 A/Low Partial N -- 4 A/Low Partial N -- 5 A/Low Partial N -- 6 A/Low Partial N -- 7 A/Low Partial N -- 8 A/Low Partial N -- 9 A/Low Partial N -- 10 A/Low Partial N -- 11 B/High Y Y Y 12 B/High Y Y Y 13 B/High Y Y Y 14 B/High Y Y Y 15 B/High Y Y Y

Part C. Patch Testing.

Patch samples were prepared by cutting one 2x4 cm piece of test patch A into an 8 mm disk using an 8 mm biopsy punch.

The gelation time of the patch samples was evaluated using a commercial texture analyzer as described in the “Hydrogel and Patch Characterization” section above. Figure 11 shows a typical force versus time plot of a patch sample evaluated immediately after activation with pH 8 buffer solution. The arrows in Figure 11 indicate the time corresponding to the lowest force in the plot. The gelation time of this sample was measured to be 25 seconds.

After the gel time test, the burst pressure of the patch samples was tested. Table 6 shows the burst pressure results. Sample 1 recorded a burst pressure of 0, indicating that the sample did not adhere to the test block after the gel test. The burst pressures of Samples 2 to 5 ranged from 10 mm Hg to 65 mm Hg. Samples 6 to 10 had a burst pressure greater than 140 mm Hg, and Sample 9 had a burst pressure of 188.2 mm Hg. Table 6 also shows the mass of the patch samples before and after the burst test. The swelling of the patch samples during the burst test varied from about 340% to about 510%.

Sample mass, g Burst pressure, mm Hg Mass after rupture, g Expansion during burst test 1 0.0164 0 0.1004 512% 2 0.0167 12 0.0847 407% 3 0.0166 48 0.0988 495% 4 0.0169 25 0.0779 361% 5 0.0166 64.4 0.0921 455% 6 0.0173 147.4 0.0801 363% 7 0.0169 120.2 0.0872 416% 8 0.0169 149.6 0.0739 337% 9 0.0178 188.2 0.0814 357% 10 0.0164 186.4 0.0862 426%

After the burst test, the patch samples were evaluated for durability and swelling in the hydrated state following the burst test. The results are summarized in Table 7. Samples 1 to 5 were immersed in a PBS solution maintained at 37°C. The samples swelled an average of 203 wt% over 24 hours. With this swelling due to hydration achieved at the conclusion of the burst test, the cumulative swelling from the dry state of patch samples 1 to 5 after about 24 hours was determined to be 1412% to 1903%. Samples 1 to 5 were invisible after 114 hours (4.8 days). Samples 6 to 10 were immersed in a PBS solution maintained at 50°C. In this accelerated aging study, each sample virtually disappeared within 24 hours.

Sample hour mass, g Mass after 24 hours, g Swelling rate after 24 hours 1 37℃ 0.1004 0.3285 227% 2 37℃ 0.0847 0.243 187% 3 37℃ 0.0988 0.2966 200% 4 37℃ 0.0779 0.2556 228% 5 37℃ 0.0921 0.2527 174% 6 50℃ 0.0801 x N/A 7 50℃ 0.0872 x N/A 8 50℃ 0.0739 x N/A 9 50℃ 0.0814 x N/A 10 50℃ 0.0862 x N/A

"x" indicates that the sample has virtually disappeared

The results indicate that biocompatible absorbable patches having a gelation time of less than 30 seconds and a burst pressure of greater than 140 mm Hg were fabricated. These patches exhibited relatively high swelling rates and overall swelling degrees, but relatively short durations of less than about 5 days. The results show that the test patches had similar persistences compared to the isolated substrate (Substrate A). These results suggest that the precursor layer and substrate can be tuned such that the persistences of the resulting hydrogel layer and substrate are similar. Alternatively, the precursor layer and/or substrate can be tuned such that the resulting hydrogel layer or substrate has a shorter persistence.

Example 3: Liver Defect Study 1 (including comparative example)

In this example, a hemostatic patch manufactured according to Example 1 was evaluated for hemostasis in a porcine liver defect model. It was compared with a commercially available fibrin suture patch.

Part A. Test and Control Patches. Three hemostatic test patches were used in this study, manufactured using substrate type A (“Test Patch A”), substrate type B (“Test Patch B”), and substrate C (“Test Patch C”) according to Example 1. A comparative fibrin sealant patch (“Control Patch A”) was purchased from Baxter (TachoSil® Fibrin Sealant Patch, 0.5 cm x 4.8 cm, product code 1144922). Each patch was cut to approximately 2x2 cm for application. The active side of the test patch was blue, and the active side of the control patch was yellow.

Part B. Preparation of animal defect model. Liver was isolated by an anterior (ventral) midline incision from a single acute (Yorkshire) pig. The animal characteristics were as follows: body weight (48.2 kg); sex (M); anticoagulant (ACT: 242). ACT was recorded prior to the first placement. Defects were made in both the right and left medial lobes of the liver. An 8 mm biopsy punch was used to penetrate the liver to a depth of approximately 4 mm. The blockage created by the punch was then removed using Metzenbaum scissors. Bleeding was assessed at this point using the Adam scale described in the literature [Adams et al, Journal of Thrombosis and Thrombolysis (2009) 28:1-5 (DOI 10.1007/s11239-008-2049-3), which is incorporated herein by reference. A target bleeding score of 3 or greater on the Adam scale is desirable. (See Figure 9 ). If the target score was not reached, the liver was again penetrated with a biopsy punch until the target score was reached. The bleeding scores of the defects that occurred in each experiment were recorded as the initial scores, as shown in Tables 8 and 9. The bleeding defects of the test patch A were severe (Experiments 2-1 and 2-2), moderate (Experiment 2-3), and mild (Experiment 2-4). The bleeding defects of the control patch A were severe (Experiments 2-1C and 2-2C), mild (Experiment 2-3C), and mild/moderate (Experiment 2-4C). Bleeding at the defect site was managed with a clean, dry gauze before applying the patches.

Test Patch A Experiment Initial score Score in 1 minute Score at 3 minutes 2-1 4 0 0 2-2 4 0 0 2-3 3 0 0 2-4 2 0 0 average: 3.25 0 0

Control Patch A Experiment Initial score Score in 1 minute Score at 3 minutes 2-1C 4 4 3 2-2C 4 3 4 2-3C 2 0 2 2-4C 2.5 0 0* average: 3.2 1.8 2.3

* The area under the patch was swollen.

Part C. Patch Evaluation Procedure and Results. A clean gauze was moistened with clean, sterile saline. The test patch A sample was placed face down on the wet gauze with the active side of the patch facing away from the gauze, but the patch can usually be placed without the gauze to achieve proper positioning, and then the gauze can be used to maintain slight pressure while the patch is applied. The gauze used to manage the bleeding at the defect site was removed from the defect site. The patch was immediately placed over the defect site, ensuring that the active side of the patch was in contact with the defect and was positioned as centrally as possible over the defect. With the hands apart, firm, even pressure was applied to the back of the patch with the wet gauze and held for 1 minute (first interval). The pressure was then slowly released and the gauze was carefully removed from the back of the applied patch. If the gauze adhered to the patch, a clean surgical instrument was gently applied to the edge of the patch or the gauze and patch were separated with minimal disruption by gentle irrigation. After the 30-second evaluation period, the 1-minute bleeding score was recorded according to the Adam scale as shown in Table 8. Then, a wet gauze was used to apply firm and even pressure to the back of the patch for 2 minutes. Once again, the pressure was slowly released and the gauze was carefully removed from the back of the attached patch. After a 30-second evaluation period, the 3-minute bleeding score was recorded according to the Adam scale as shown in Table 8. The edges of the patch were then gently pinched using a pair of forceps to test for adherence. This process was repeated with 3 additional defects, for a total of 4 experiments using Test Patch A. All the test patch samples adhered well to the target site and were not affected by the removal of the wet gauze. In addition, the edges of the test patch samples did not pull upward when pulled/pinch-ed with forceps. No stretching was observed in any of the test patch samples. The results show that hemostasis was achieved within 1 minute of patch placement in all experiments using Test Patch A.

The above procedure was repeated for the control patch A with slight modifications. For the control patch A experiments 2-3 and 2-4, the target bleeding score was lowered from > 3 to > 2 due to the poor performance of the control sample in experiments 2-1C and 2-2C. The results are shown in Table 9. For the control patch A experiment 2-4C, the bleeding score was recorded as 0 after 3 minutes of placement, but the bottom of the patch was swollen. When pressure was applied, blood flowed out from under the patch and bleeding continued. This experiment was considered non-hemostatic. According to the results, despite the lower target bleeding score in the second two experiments, none of the experiments using the control patch A achieved hemostasis after 3 minutes of placement. In addition, the control patch A sample was observed to not adhere to the target site and to fall off easily. When removing the wet gauze, great care should be taken not to allow the patch to touch the attachment site.

Test Patch B and Test Patch C were evaluated for the hepatic defects that occurred for Control Patch A Experiments 2-2C and 2-3C, respectively, after these control patch samples allowed continued severe or mild bleeding for 3 minutes, respectively. As shown in Table 10, both test patch samples were able to restore hemostasis within 1 to 3 minutes. The initial placement of Test Patch B was not positioned centrally over the defect site. The second Test Patch B was placed over the defect site 1 minute after the initial placement. Hemostasis was achieved 3 minutes after the first placement, corresponding to 2 minutes after the second placement.

Sample Initial score Score in 1 minute Score at 3 minutes Test Patch B 4 4* 0 Test Patch C 2 0 0

* The initial placement was not centered on the wound and a second test patch B was placed 1 minute later.

Part D. Additional Patch Evaluation. Test Patch A was also evaluated by placing it in an uneven position on the defect created on the liver surface using a scalpel. The channel-shaped defect was approximately 3 mm deep and 5 mm long. Test Patch A was cut to a size of 2x4 cm, soaked in saline, folded in half lengthwise, and placed on the defect site. Figure 10a shows Test Patch A after initial placement. Pressure was applied to the test patch sample using a wet gauze. As shown in Figure 10b, hemostasis was achieved in 1 minute at the location where the test patch contacted the defect. Figure 10b shows that persistent bleeding occurred from the defect area that did not contact the test patch.

This example demonstrates that the hemostatic patch manufactured according to Example 1 performed significantly better than commercially available fibrin suture patches in achieving hemostasis at both 1 and 3 minutes after placement into a porcine liver defect. The reactive precursor of the hemostatic patch allows for both flat and non-flat placement and allows manual compression for a short period of time after placement, resulting in a fast, adaptable, and easy-to-use patch for mild to severe hepatic bleeding defects.

Example 4: Liver Defect Study 2 (including comparative example)

In this example, a hemostatic patch manufactured according to Example 1 was evaluated for hemostasis in a porcine liver defect model. It was compared to a commercially available fibrin suture patch.

Part A. Test and Control Patches. A series of hemostatic test patches were prepared in this study using description type A (“Test Patch A”) according to Example 1. A comparison sealant patch containing human fibrinogen and human thrombin (“Control Patch B”) was purchased from Johnson and Johnson (Evarrest® Fibrin Sealant Patch, 5.1 cm x 10.2 cm, product code EVT5024). Each patch was cut to approximately 2x2 cm for application. The active side of the test patch was blue and the active side of the control patch was yellow.

Part B. Preparation of animal defect model. Liver was isolated by an anterior (ventral) midline incision from a single acute (Yorkshire) pig. The animal characteristics were as follows: body weight (57.4 kg); sex (F); anticoagulant (ACT: 294). ACT was recorded prior to the first batch. Defects were made in both the right and left medial lobes of the liver. An 8 mm biopsy punch was used to penetrate the liver to a depth of approximately 4 mm. The blockage created by the punch was then removed using Metzenbaum scissors. Bleeding was assessed at this point. A target score of 3 or greater on the Adam scale was desirable (see Figure 9). If the target score was not achieved, the liver was penetrated again with a biopsy punch until the target score was achieved. The bleeding scores of the defects that occurred in each experiment were recorded as the initial scores as shown in Tables 11 and 12. All test patch A bleeding defects were severe. Control patch B bleeding defects were moderate (Experiment 3-1C) or severe (Experiments 3-2C, 3-3C, and 3-4C). Bleeding at the defect site was managed with clean, dry gauze.

Test Patch A Experiment Initial score Score in 30 seconds Score in 1 minute Score at 3 minutes 3-1 4 0 0 0 3-2 4 0 0 0 3-3 4 0 0 0 3-4 4 0 0 0 average: 4 0 0 0

Control Patch B Experiment Initial score Score in 30 seconds Score in 1 minute Score at 3 minutes 3-1C 3 0.5 0.5 0.5 3-2C 4 3 4 0.5 3-3C 4 1 3* 3 3-4C 4 2 2 0** average: 3.8 1.6 2.4 1

* The patch was removed by the gauze during the hemostasis test.

** The patch subsequently fell off and the wound required re-treatment.

Part C. Patch Evaluation Procedure and Results. In this example, the procedure described in Example 2, Part C was followed, with the modification that the first scoring was performed after 30 seconds. All Test Patch A samples adhered well to the target site and were not affected by removal of the wet gauze. In addition, the edges of the Test Patch A samples did not pull up when pulled/pinched with forceps. No stretching was observed in any of the Test Patch A samples. As shown in Table 11, all experiments using Test Patch A achieved hemostasis within 30 seconds after attachment.

Results for the Control Patch B are shown in Table 12. Only one Control Patch B sample (Control Patch B Experiments 3-4C) achieved hemostasis after 3 minutes. However, the patch detached and bleeding resumed later in the study. The detached patch was later located in the thoracic cavity. The remaining three Control Patch B experiments showed either exudation (Control Patch B Experiments 3-1C and 3-2C) or moderate bleeding (Control Patch B Experiment 3-3C) at the 3-minute mark. Great care must be taken not to disturb the Control Patch when removing the wet gauze. When assessed at the 3-minute mark, Control Patch B was observed to be adhered to the wound only where bleeding was occurring. The area of the Control Patch extending beyond the wound was not adhered to the tissue and remained in a loose/lifted flap state.

Part D. Additional Patch Evaluation. Test Patch A was further evaluated using multiple non-flat (convex) placements on the partially resected liver lobe. The placements were a pre-moistened 2x4 cm patch, a 2x4 cm dry patch, and a 2x2 cm dry patch. It was observed that applying pressure to the dry patch was less difficult than the pre-moistened patch, due to less slippage. After applying all three patches, hemostasis was achieved throughout the defect. Each placement achieved hemostasis in the area in contact with the corresponding patch.

This example shows that the hemostatic patch manufactured according to Example 1 performed significantly better than the commercially available fibrin/thrombin sealing patch in achieving hemostasis for moderate to severe bleeding at 30 seconds, 1 minute, and 3 minutes after application to a porcine liver defect. Despite the inclusion of the reactive agent (thrombin) in the fibrin/thrombin sealing patch, the patch did not actually seal the wound as well as the hemostatic patch. Pick tests at the edge of the hemostatic patch showed no delamination, but the fibrin/thrombin patch adhered only to the wound. The control patch detached in two out of four experiments.

Example 5: Study of Cardiovascular Defects

In this example, a hemostatic patch manufactured according to Example 1 was evaluated for hemostasis after placement at various locations in a porcine cardiovascular defect model.

Part A. Test Patches. In this study, a set of hemostatic patches was prepared using the type A described in Example 1 (“Test Patch A”). All batches were made with the patches dry. The patches can be made flexible by applying saline solution directly to the patches after batching or by applying pressure with pre-moistened gauze.

Part B. Initial preparation of the animal defect model. A female acute (Yorkshire) pig weighing 60 kg was used in this study. The carotid artery was exposed by an incision of the skin over the midline of the neck. Blunt dissection was performed through the underlying subcutaneous tissue and muscle. The muscle was retracted, and the fascia surrounding the target vessel was resected from the vessel surface. The lateral branches of the vessel were ligated using silk sutures and clips. The vessel was temporarily occluded after proximal and distal control of the artery using a vascular loop and vascular clamp. The arteriotomy was performed, and the graft (Gore Acuseal) was anastomosed end-to-end using nonabsorbable sutures. Upon completion of the anastomosis, the vascular loop and clamp were removed to reestablish blood flow.

Each femoral artery was exposed through a groin incision. Blunt dissection was performed through the underlying subcutaneous tissue and muscle. The muscles were retracted, and the fascia surrounding the target vessel was resected from the vessel surface. The lateral branches of the vessel were ligated using silk sutures and clips. After obtaining proximal and distal control of the artery using a vascular loop and vascular clamp, the vessel was temporarily occluded.

Part C. Defect generation, patching procedures, and results.

Procedure 1: Femoral placement. A 3- to 5-cm segment of the left femoral artery was occluded using a clamp and a vascular loop. Four punctures were made in the vessel using a 25-gauge needle to simulate the suture line of the vascular repair procedure. The artery was declamped to ensure that a bleeding defect had been created and to assess bleeding using the Adam scale. Pulsatile bleeding was determined to be severe (Adam scale score 4). The artery was re-clamped to occlude blood flow and to clean up any blood that had pooled in the area. Test patch A was cut to approximately 1 x 1.7 cm. The dry test patch was placed over the defect, covering the defect with the blue side facing the target bleeding. Manual pressure was applied to the test patch for 30 seconds using pre-moistened gauze. Both the vascular loop and clamp were then removed to restore blood flow to the area. After 30 seconds of manual pressure, the gauze was removed. The patch was assessed for hemostasis and adhesion. Arterial flow was assessed by checking for pulses on both sides of the patch. Thirty seconds after patch placement, hemostasis was achieved at the site and good adhesion to the surrounding tissues was observed. Approximately 1 hour after placement, the hind limb was “exercised” to simulate movement. The patch remained attached to the defect and surrounding tissues during and after this movement. Pulses were assessed on both sides of the patch (distal and proximal).

Procedure 2: Femoral placement during pulsatile flow. Working in the same area as described in Procedure 1, a 25-gauge needle was used to puncture the vessel adjacent to the defect in Procedure 1 once. The pulsatile bleeding was determined to be severe (Adam scale score 4). The hole was immediately covered by manual compression until patch placement was imminent. Manual compression was removed, and a dry patch measuring approximately 1.5 x 2 cm was immediately placed over the active bleeding site. Manual pressure was applied to the patch for 30 seconds using pre-moistened gauze. After 30 seconds of manual pressure, the gauze was removed. The patch was assessed for hemostasis and adhesion. Arterial flow was checked by checking for pulses on both sides of the patch. Thirty seconds after patch placement, hemostasis was achieved at the site and good adhesion to the surrounding tissues was observed. Approximately 1 hour after placement, the hind limb was “exercised” to simulate movement. The patch remained attached to the defect and surrounding tissue during and after these movements. Pulses were detected on both sides (distal and proximal) of the patched area.

Procedure 3: Femoral wrapping. A 3- to 5-cm segment of the right femoral artery was occluded using a clamp and a vascular loop. A small longitudinal defect was created along the artery using a scalpel. The defect was closed with 2 to 3 sutures. The proximal clamp was removed to identify the bleeding defect and assess it as severe pulsatile bleeding. The clamp was reapplied to occlude the blood flow and to clean the area of blood that had pooled. A dry patch was placed under the defect with the blue side facing upward. The patch was then hydrated with saline and wrapped around the defect, contacting the blue side of the target bleeding site. Manual pressure was applied to the patch for 30 seconds using pre-moistened gauze. After 30 seconds of manual pressure, the gauze was removed. Hemostasis and adhesion of the patch were assessed. Arterial flow was assessed by checking the pulse on both sides of the patch. Thirty seconds after patch placement, hemostasis was achieved at the site and good adhesion to surrounding tissues was observed. Approximately 15 minutes after placement, the hind limb was “exercised” to simulate movement. The patch remained attached to the defect and surrounding tissues during and after this movement. Pulses were detected on both sides of the patched area (distal and proximal).

Procedure 4: Placement on the bleeding suture line. The animals were administered heparin, and the procedure was completed with anticoagulated blood. The right carotid artery was isolated and the graft (Gore Acuseal, ECH060020A) was anastomosed end-to-end. With active blood flow through the artery and the graft, the suture was manipulated/removed at the distal anastomosis to create a bleeding site. Bleeding was assessed as 3 (moderate) using the Adam scale. Two pieces of test patch A (2x2 cm) were placed along the suture patch to cover the defect, with the blue side facing the target bleeding site. Manual pressure was applied using pre-moistened gauze and pressure was maintained for 30 seconds. After 30 seconds of manual pressure, the gauze was removed and the hemostasis and adhesion of the patch were assessed. Hemostasis was achieved after 30 seconds. The patch adhered to the suture line but was minimally adherent to the graft. It was observed that after anticoagulation, the suture closure of the suture line functioned as well as before anticoagulation.

Procedure 5: Placement into the graft defect. This procedure was completed using anticoagulated blood. The graft was punctured using a 14-gauge needle at the same site as described in Procedure 4. The puncture was assessed to ensure that there was a stable and adequate flow of blood from the defect (ADAM score 3). Test Patch A was placed over the graft defect. Manual pressure was applied to the patch using pre-moistened gauze for 30 seconds. After 30 seconds of manual pressure, the gauze was removed. The patch was assessed for hemostasis and adhesion. After 30 seconds, sealing of the target bleeding was observed. The extent of patch adhesion to the graft was observed to be minimal. The patch could be removed from the bleeding site using forceps.

This study demonstrated that the deployment of Test Patch A successfully closed defects commonly encountered in cardiovascular procedures, including pulsatile femoral perforations and end-to-end anastomosis between the carotid artery and the graft. In all cases where Test Patch A was applied, hemostasis (or closure) was achieved within 30 seconds after deployment. Even after flexion of the hind limb, the patch remained stable and adhered to the tissue at the deployment site. The patch successfully controlled bleeding from the graft. Furthermore, the patch closure performance remained consistent even after the animals were administered heparin.

Example 6: Study of Orthopedic and Cardiovascular Defects

In this example, a hemostatic patch manufactured according to Example 1 was evaluated for hemostasis after placement at various locations in an acute, non-GLP porcine orthopedic and cardiovascular defect model.

Part A. Test Patches. In this study, a set of hemostatic patches was prepared using the type A described in Example 1 (“Test Patch A”). All batches were made with the patches in a dry state and with pressure applied with a wet gauze. Both 2x2 cm and 2x4 cm patches were used. The patches could be made flexible by applying pressure with a pre-moistened gauze after batching.

Part B. Initial preparation of the animal defect model. A male acute (Yorkshire) pig weighing 27 kg was used in this study. The skin was incised to expose the tibial shaft. Blunt incision was then made through the underlying subcutaneous tissue and muscle. The muscle was retracted, and the fascia around the target area was resected from the bone surface. A dental drill with a 2-3 mm ball-tipped bit was used to create a target cortical hemorrhage ligation. The defect site was irrigated with saline to prevent tissue heating during creation and to remove foreign bodies.

The skin was then incised to expose the femoral head. Blunt dissection was then performed through the underlying subcutaneous tissue and muscle. The muscles were retracted, and the fascia around the target area was resected from the bone surface. A dental drill with an appropriate 2-3 mm ball-tipped bit was used to create a target cortical hemorrhage union. The defect site was irrigated with saline to prevent tissue heating during creation and to remove foreign bodies.

Finally, each femoral artery was exposed through a groin incision. Blunt dissection was performed through the underlying subcutaneous tissue and muscle. The muscles were retracted, and the fascia surrounding the target vessel was resected from the vessel surface. The lateral branches of the vessel were ligated using silk sutures and clips. After obtaining proximal and distal control of the artery using a vascular loop and vascular clamp, the vessel was temporarily occluded.

All bleeding assessments were performed using the Adam scale.

Part C. Defect generation, patching procedures, and results.

Procedure 1: Tibial shaft defect. A defect measuring approximately 3 mm in diameter and approximately 4 mm in depth was created in the tibial shaft using a dental drill and ball drill bit. Bleeding was noted and assessed as very minor (ADAM score 1). The patch was cut to approximately 1x2 cm. The patch was placed so that the blue side was directed toward the target bleeding site, covering the defect. Manual pressure was applied to the patch for 30 seconds using pre-moistened gauze. The gauze was removed after 30 seconds of manual pressure. The patch was assessed for hemostasis and adherence. The site was observed to be sealed within 30 seconds of patch placement. Over time, the site was observed to have evidence of persistent bleeding under the patch, but the site remained sealed and the patch remained well adhered.

Procedure 2: Tibial shaft giant defect. A larger defect (approximately 6 mm in diameter and 9 mm in depth) was created in the same area as described in Procedure 1 using a dental drill and ball drill bit. Bleeding was noted and assessed as very mild (Adam score 1). A 6-mm biopsy punch was used to cut 2x2-cm patch pieces into a disc shape that matched the size of the defect. Two of these discs were placed into the defect using forceps, with the blue side of the first patch facing the target bleeding site in the defect bed. Each subsequent patch was stacked on top of the previous one with the blue side facing the previous one. They were placed to address bleeding from the wall of the defect. Manual pressure was applied to the upper patch for 30 seconds using pre-moistened gauze. After 30 seconds of pressure, the gauze was removed. Hemostasis of the affected area and adherence of the patches were assessed. Hemostasis was observed 30 seconds after patch placement.

Procedure 3: Femoral condyle defect. A defect measuring approximately 6 mm in diameter and 3 mm in depth was created in the femoral condyle using a dental drill and a ball drill bit. Bleeding was noted and assessed as very mild (Adam score 1). A 6-mm biopsy punch was used to cut a 2x2-cm piece of test patch A into a disc shape that matched the size of the defect. The disc was placed into the defect using forceps, with the blue side of the patch facing the target bleeding site. Pressure was applied to the patch using a pre-moistened gauze using the plunger of a 1-ml syringe for 30 seconds. The gauze was removed after 30 seconds of pressure. The patch was assessed for hemostasis and adhesion to the site. Hemostasis was observed 30 seconds after patch placement.

Procedure 4: Deep femoral condyle defect. A defect measuring approximately 6 mm in diameter and 9 mm in depth was created in the femoral condyle using a dental drill and a ball drill bit. Bleeding was noted and assessed as mild (Adam score 2). A 6-mm biopsy punch was used to cut 2x2 cm test patch A disc-shaped pieces. Four of these discs were placed within the joint with the blue side of the first patch facing the target bleeding site in the defect bed. Each subsequent patch was stacked on top of the previous one with the blue side facing the previous patch. They were placed to address bleeding from the wall of the defect. Pressure was applied to the patches using a pre-moistened gauze using a plunger from a 1-ml syringe for 30 seconds. After 30 seconds of pressure, the gauze was removed. The patch was assessed for hemostasis and adhesion to the site. Hemostasis was observed 30 seconds after patch placement.

Procedure 5: Femoral artery suture defect. A 3- to 5-cm segment of the femoral artery was occluded using a clamp and a vascular loop. Two holes were made in the vessel using a 25-gauge needle to simulate the suture line of a vascular repair procedure. The artery was released to confirm the presence of a bleeding defect and to assess bleeding using the Adam scale. Pulsatile bleeding was assessed as severe (Adam score 4). The artery was re-clamped to occlude blood flow and to clean up any blood that had pooled in the area. A piece of gauze was cut and soaked in clean saline. A 2x4 cm patch was placed on the soaked gauze with the blue side facing the opposite side of the gauze. The patch/gauze pair was then pushed under the artery with the blue side of the patch facing the bleeding site. The user held the ends of the gauze and lifted them toward each other until the ends touched. Pressure was then applied to the patch-patch contact area (“tail”) so that the central portion of the patch encircled the vessel and the tails of the patches adhered to each other. Care was taken to ensure that the passage formed by the two tails was not directly over the bleeding site. Manual pressure was then applied to the patch through gauze for 30 seconds. After 30 seconds of manual pressure, the gauze was removed. Both the vascular loop and the clamp were then removed to restore blood flow to the site. Arterial flow was assessed by checking for pulses on both sides of the patch. Hemostasis and adherence of the patch were then assessed. The tails of the patch were trimmed with Metzenbaum scissors so that approximately 2 to 3 mm of tail remained along the length of the arterial patch. At the 30-second mark, hemostasis was achieved at the patch site, good adherence to the artery, and pulses were observed both distal and proximal to the patch.

Procedure 6: Contralateral femoral artery defect. The procedure described in Procedure 5 was applied to the contralateral femoral artery. The resulting pulsatile hemorrhagic involvement was assessed as severe (ADAM score 4). Again, the patch site was observed to have achieved hemostasis at the 30-second mark, was well adhered to the artery, and had pulses both distal and proximal to the patch.

In a further study, the test patch A was evaluated in chronic carotid artery occlusion using a patch occlusion model. Seven days after implantation in the model, the test patch A resulted in stable vascular repair with no signs of bleeding as assessed by angiography.

This study demonstrated that placement of the Test Patch A successfully closed condyle and diaphyseal bone defects with minimal to moderate bleeding, and bilateral pulsatile femoral artery defects with severe bleeding. In each case, hemostasis (or closure) was achieved within 30 seconds of application of the dry patch. A syringe plunger was successfully used to apply pressure to the patch placed in the deep bone defect. An alternative wrapping-type placement method was successfully used to treat pulsatile femoral artery perforations.

Example 7: Combined study of soft tissue and orthopedic defects

This example demonstrates the use of both a soft tissue patch and an orthopedic surgical patch on a patient.

Part A. Test Patches and Control Products. Three types of hemostatic patches were used in this study, each using substrate type A (“Test Patch A”), substrate type B (“Test Patch B”) and substrate C (“Test Patch C”), all prepared according to Example 1. The control product was a 2 mm thick, water-insoluble porcine gelatin sponge (Surgifoam® absorbable gelatin sponge, Johnson and Johnson, product code 1975) to which recombinant thrombin (Baxter, Recothrom®) was added (“Control Patch C”). Both dry and pre-moistened batches were attempted for each sample.

Part B. Preparation of the Animal Defect Model. In a training laboratory setting, surgeons were provided with the patch described in Part A. A midline incision was made along the anterior (ventral) line of a single acute (Yorkshire) pig, and the liver was isolated. The animal characteristics were as follows: body weight (48.2 kg); sex (M); anticoagulant (ACT: 242). ACT was recorded prior to the first placement. Defects were made in both the right and left medial lobes of the liver and the spleen. An 8-mm biopsy punch was used to initially penetrate each organ to a target depth of approximately 7 mm. A target depth of approximately 2 mm was used later. The blockage created by the punch was then removed using Metzenbaum scissors. Bleeding was assessed at this point. A target score of 3 or greater on the Spot Grade SBSS was desirable. If the target bleeding score was not achieved, the organ was re-penetrated using the biopsy punch until the target score was achieved. Bleeding defects were moderate to severe. Bleeding at the defect site was managed with clean, dry gauze prior to product placement.

Part C. Patch Evaluation Procedure and Results. A clean gauze was moistened with clean sterile saline. The test patch sample was placed face down on the wet gauze with the blue surface of the patch facing away from the gauze. The gauze that was controlling the bleeding was removed from the defect. The patch was placed directly over the defect so that the blue side of the patch was in contact with the defect and as centrally over the defect as possible. With the hand open, the back of the patch was pressed firmly and evenly with the wet gauze, holding it there for 30 seconds. The pressure was then carefully released and the gauze was carefully removed from the back of the attached patch. If the gauze was stuck to the patch, the gauze and patch were separated by gently applying a clean surgical instrument to the edge of the patch or by gentle irrigation, minimizing disruption. After the 30-second evaluation period, the 30-second bleeding score was recorded based on the Spot Grade SBSS. The edges of the patch were then gently pulled with a pair of forceps to test for adherence. This procedure was repeated for each patch sample. For each patch sample, a modified procedure was used in which the patches were applied without pre-wetting the gauze.

Part D. Observation.

Test Patch A produced hemostasis with each application. When pressure was applied to the hollow defect and the patch was pre-wetted, it was more effective in sealing the defect than when applied dry over the hollow core organ defect. When the pre-wetted patch was applied, there was no patch bulging or doming, and no red blood core formed over the patch over the hollow core defect. Test Patch B provided similar results to Test Patch A, producing hemostasis with each application. The success rates of application of Test Patches A and B improved with the surgeon’s experience with the patch and the length of time after patch placement. A number of samples of Test Patch C were attempted, but in each case the patch adhered to the gauze during placement. Removal of the gauze resulted in tearing of the substrate and re-bleeding. Control Patch C was successfully used to produce hemostasis in both the liver and spleen. However, Control Patch C did not adhere well to the tissue and the surgeons were concerned that the product was at high risk of detachment. Both the test and control patches produced a “dome effect” of blood swelling under the patch/product at the defect site. The dome effect was generally prevented by applying pressure to the applied patch/product.

According to the results, Test Patch A and Test Patch B were good adhesion to tissue, relatively easy to use patches, and showed rapid hemostasis. Test Patch C could not achieve sustained hemostasis with the process used. The excessive porosity of the substrate of Test Patch C is thought to be related to too much blood flowing from the defect through the active side into the substrate because the hydrogel can migrate through the highly porous substrate. This study showed that the active side composition used with an appropriate substrate affects the performance and usability of the patch. Control Patch C showed poor adhesion to tissue.

Example 8: Study of simulated cervical defects

This example demonstrates the use of a conical mandrel to achieve hemostasis at a simulated cervical defect site.

Part A. Test Patches. A set of cone-shaped hemostatic patches were prepared using the general procedure of Example 1 using the type A substrate. The patches were further formed into a cone shape through a series of manufacturing steps as follows: The patches were cut along the sides to the central portion of the patch. They were then slightly heated to form a roughly cone shape. The overlapping cut portions were then clamped together to hold the shape until the PEG cooled.

Part B. Preparation of animal defect model. A single acute (Yorkshire) pig was opened and the pig abdominal wall was separated. The anticoagulant level (ACT) was greater than 300 before the first placement. An 8 mm biopsy punch was used to penetrate the abdominal lateral wall to a target depth of approximately 7 mm. The obstruction created by the punch was then removed using Metzenbaum scissors. Bleeding was assessed at this point. A Spot Grade SBSS score of 3 was achieved. Bleeding at the defect site was controlled with clean, dry gauze prior to product placement.

Part C. Patch Evaluation Procedure and Results. The test patch sample was placed on the defect site with the blue surface of the cone-shaped patch facing the defect site. The mandrel handle was held and the cone-shaped portion of the mandrel with the cone patch was pressed against the defect site. Gentle but constant pressure was applied to the patch using the mandrel for 30 seconds. The pressure was then carefully released and the mandrel was carefully removed from the convex (back) surface of the applied patch. The patch was observed to adhere slightly to the mandrel and the mandrel was separated from the patch with minimal disturbance using clean surgical instruments. Hemostasis was assessed after a 30-second evaluation period. A modified procedure was used in the second application, where a wet piece of gauze was placed between the cone-shaped patch and the mandrel before pressing the patch onto the defect site with the mandrel. No adhesion of the patch to the mandrel or gauze was observed during the removal of the mandrel and gauze after the patch was applied. Hemostasis was assessed after a 30-second evaluation period.

Part D. Observation.

Both applications achieved hemostasis for 30 seconds and the patches adhered well to the defect site. In the first application, the patches were attached to the mandrel and the hemostasis was lost when the mandrel was removed, but in the second application, the hemostasis was maintained even after the mandrel was removed using a modified placement procedure. The experimental results demonstrate that the use of a shaped mandrel allows for the placement of preformed patches in sites that are difficult to manually apply (“remote sites”). The results also demonstrate that the use of a preformed patch and a mandrel shaped accordingly can be advantageously used to align, place, and apply the preformed patch to both remote and non-remote sites. The shaped mandrel allows for more consistent pressure to be applied across the entire surface of the preformed patch that contacts the defect. The consistent pressure reduces the potential for bleeding under the patch, thereby promoting rapid hemostasis. The results suggest that a conical patch and a corresponding conical mandrel, as shown in FIGS. 12a and 12b , are suitable for achieving hemostasis of cervical bleeding defects.

Example 9: Preparation of a flexible hemostatic patch having a compression substrate

This example describes a compression process for preparing a flexible hemostatic patch.

Part A. Compression Test of the Description.

In this study, two types of substrates were used as shown in Table 13. Substrates E and F were both foamed gelatin/collagen substrates purchased from different commercial suppliers. The commercial foamed gelatin substrates were heat cross-linked in an oven for several hours according to the time and temperature ranges described above. The substrate samples were approximately 10 cm wide, 20 cm long and 7 mm thick.

Description type characteristic Initial thickness E Foamed gelatin/collagen 7 mm F Foamed gelatin/collagen 7 mm

Substrates E and F were compressed using a calendar roller. For convenience, the compression was performed using a pasta roller at a setting where the distance between the near surfaces of the calendar rollers (i.e., the gap) was about 5 mm. Figures 15a and 15b are SEM images of the surface of the substrate E sample before and after compression, respectively. Figures 15c and 15d are SEM images of the surface of the substrate F sample before and after compression, respectively. Figures 15a to 15d were captured using a 25X magnification with backscattering. The difference in the pore structures of substrates E and F before compression can be visually seen in Figures 15a and 15c. Both Figures 15a and 15c show various pore sizes, but in general, the larger pores in Figure 15a are larger than the larger pores in Figure 15c. Additionally, the scaffold of material surrounding the large pores of substrate E (Fig. 15a) is much thinner than the scaffold of material surrounding the pores of substrate F (Fig. 15c). Referring to Fig. 15b, the pore structure of substrate E after compression appears to be collapsed and destroyed, generally lacking the thin scaffolding material seen in Fig. 15a. Referring to Fig. 15d, the pore structure of substrate F after compression appears similar to that of the uncompressed sample, but in a denser version (Fig. 15c). Table 14 shows the average pore area fraction and average pore diameter for the SEM images of Figs. 15a-15d as determined using ImageJ image analysis software. The measurement of the average porosity area fraction is semi-quantitative because it captures both the pores at the image surface and some pores below the image surface. The data in Table 14 indicate that the average porosity area fractions of the uncompressed and compressed samples are similar. The results indicate that there are significant differences in the foam/scaffold structure between substrates E and F.

Description E Description F measurement Uncompressed/
Fig. 15a Compressed/
Fig. 15b Uncompressed/
Fig. 15c Compressed/15d Average porosity area fraction 50.2% 50.8% 53.7% 53.8%

The Substrate E sample set was further evaluated for fluid absorption, flexural strength, shear force, compressive strength, and conformability before and after compression. Results for ten duplicate samples for each measurement are reported in Table 15. Fluid absorption was tested by weighing ten uncompressed samples both dry (initial dry weight) and after immersion in saline solution for 15 seconds (final weight). The fluid absorption for each sample was calculated as (final weight - initial dry weight)/100% initial dry weight. The average fluid absorption for the uncompressed Substrate E was reported as the average of the fluid absorption of the ten uncompressed samples. Flexural strength was measured by three-point bending testing on ten individual dry, uncompressed samples of Substrate E using a texture analyzer machine (model TA-XT Plus C) equipped with a three-point bending apparatus, in accordance with ASTM D790-17, which is incorporated herein by reference. The size of each specimen was approximately 2.5 cm in width and 6.5 cm in length. The maximum shear force was measured by placing the dry, uncompressed specimen on the cantilever and applying force. The maximum shear force was recorded as the force at failure. Each specimen was approximately 2.5 cm in width and 6.5 cm in length and was held in place by a 1 cm test grip. The column strength (or maximum compressive force) was measured by subjecting ten dry, uncompressed samples of Substrate E to uniaxial compression individually using a texture analyzer machine (model TA-XT Plus C). Each specimen was a dog bone-shaped test sample measuring 2.5 cm in width and 7.5 cm in length. The column strength was recorded as the force at failure. Compliance was tested by wrapping the dry samples on a ½ inch mandrel. A positive compliance was indicated when no cracking or failure occurred in the sample during the test, and the results were reported as the percentage of positive samples per ten samples tested. The average thickness of each sample was measured with a caliper.

The above tests were repeated using a set of 10 compressed substrate samples for each test. The results are shown in Table 15. Comparing the average measurements of the uncompressed substrate samples to the average measurements of the compressed substrate samples, there was essentially no change in fluid absorption (360% vs. 356%), but the mechanical properties of the samples did change. The compressed samples had lower average flexural, shear, and column strengths, but all of the compressed samples (10/10) were able to be molded to a ½ inch diameter mandrel. Only 3 of the 10 uncompressed samples passed the same ½ inch mandrel test. The results show that the compression of the substrate did not change the fluid absorption but did impart flexibility/conformability to the substrate. The results also show that the compressed samples retained a greater percentage of their original compressive and tensile strength compared to their shear strength (maximum shear force), which is evidenced by the column strength and flexural strength measurements. The shear strength of the compressed samples was approximately 10% of the shear strength of the uncompressed samples. These results suggest that compressing substrate E using calendering results in significant shear-induced failure, yet the substrate is soft enough to remain relatively stiff. The results specifically demonstrate that compression via calendering can impart flexibility to cross-linked gelatin substrates through collapse of the pore structure without measurable loss of fluid absorbency or substantial loss of stiffness. The results also show that the thickness variability of the compressed substrate samples was lower than that of the uncompressed substrate samples.

Description E measurement Uncompressed Compressed fluid absorption rate
% mass change 360% 356% Bending strength 212.8 g 38.8 g Maximum shear force 60.6 g 6.3 g Column strength, lb force 318.9 115.6 compatibility 3/10 10/10 Average thickness, mm 7.12 mm, standard deviation 0.64 mm 5.11 mm, standard deviation 0.30 mm

Additional fluid absorption data was collected as a function of time for both uncompressed and compressed samples. Figure 19 shows the average fluid absorption when the substrate samples were soaked for 15 seconds, 1 minute, 5 minutes, and 10 minutes. The average fluid absorption for the uncompressed and compressed substrate samples at 20 hours (not shown in the plot) was approximately 1200%. The results show that the substrate initially absorbed the fluid rapidly and then the absorption level stabilized after approximately 10 minutes. The average fluid absorption percentages for the uncompressed and compressed substrates for a given measurement time were generally within the measurement error range.

Part B. Processing and testing of coated substrates.

The coated substrates were prepared by melt coating a dry mixture of two hydrogel precursors onto a set of pressed substrate E samples. The substrate samples were dried in an oven at ambient air temperature of 35 °C for 18 h or until the oven relative humidity was less than 5% to prepare them for coating. The thickness of each substrate sample after drying was approximately the same as before drying. For each of the coated substrate samples, the first hydrogel precursor was an eight-arm polyethylene glycol-based precursor having a molecular weight of 15,000 Da and succinimidyl glutarate (SG)-functionalized end groups (8A15k PEG SG, Jenkemusa). The second hydrogel precursor was an eight-arm polyethylene glycol-based precursor having a molecular weight of 20,000 Da and HCl-chlorinated amine-functionalized end groups (8A20k PEG amine-HCl, Jenkemusa). The first and second precursors were measured in powder form and then melt mixed in a glove box with trace amounts of FD&C Blue#1 in a heated roller system at a temperature greater than 45°C. The molten precursor mixture was delivered to a liquid distribution system (FOM Coater, FOM Technologies). A single coating layer of the molten mixture was applied to each substrate sample under inert gas conditions. The precursors were applied through a heated slot die head positioned 4.5 mm apart above the bottom surface of the substrate, which was approximately 5 mm thick. In this process, substrate coating involved injecting the molten mixture into the substrate due to compression of the substrate by the slot die head. The average thickness of the precursor impregnated region (“precursor/substrate network region”) of each substrate was approximately 0.25 mm, and typically extended at least approximately 0.05 mm above the substrate surface. The mixed precursor-coated substrates were allowed to solidify at room temperature under inert gas conditions. The thickness of each coated substrate measured approximately 5.25 mm.

One of the coated substrates (Sample 1) was kept as an “uncompressed sample”, while the remaining coated substrate samples (Samples 2 to 4) were compressed after coating using a calender roller. SEM images of representative portions of the surfaces of Samples 1 to 4 are shown in FIGS. 16a to 16d, respectively. For the uncompressed sample (Sample 1), FIG. 16a shows that the coated sample has relatively non-uniform cracks on its surface, including relatively large cracks compared to the post-compressed cracks in FIGS. 16b to 16d. (FIG. 16a is at a lower magnification than FIGS. 16b to 16d.) The large cracks seen in FIG. 16a are a result of sample handling/transportation and demonstrate the stiffness and brittleness of the solidified precursor after coating if no strain relief measures are provided. Despite the brittleness of the solidified precursor in FIG. 16a (Sample 1), the precursor was observed to adhere well to the substrate. For samples 2 to 4, post-coating compression was performed using pasta rollers at a setting corresponding to the distance between the near surfaces of the calendar rollers (i.e., gap). One coated sample (sample 2, Fig. 16b) was compressed with a setting corresponding to a gap of about 5 mm. Another coated sample (sample 3, Fig. 16c) was compressed with a setting corresponding to a gap of about 2 mm. Another coated sample (sample 4, Fig. 16d) was subjected to a two-stage compression, first with a gap of about 5 mm and then with a gap of about 2 mm. Figures 16b to 16d show that compression of the coated substrate results in surface failure, while direct compression with a gap of 2 mm (sample 3, Fig. 16c) results in significant surface failure. The SEM image of Sample 4 (Fig. 16d) shows that the two-step compression can relieve some of the strain in the first compression step and induce additional fracture in the second compression step, providing more consistent fracture. The SEM images of Samples 2-4 (Figs. 16b-16d) qualitatively show that the compressed Samples 2-4 are less brittle than the uncompressed Sample 1 (Fig. 16a) as there are no non-uniform/wide cracks as shown in Fig. 16a. All samples showed good adhesion of the precursor to the substrate even during handling and transportation.

Figures 17a and 17b show SEM images of cross-sections of representative portions of Sample 1 and Sample 2. Uncompressed Sample 1 (Figure 17a) and compressed Sample 2 (Figure 17b) have similar base substrates to the uncompressed and compressed substrates described in Part A. In particular, the base substrate of Sample 1 (Figure 17a) exhibits relatively large pores surrounded by a thin gelatin scaffold. The base substrate of Sample 2 (Figure 17b) exhibits a collapsed/fractured pore structure. The precursor/substrate network region (“network”) of Sample 1 measured about 200 to 230 microns thick. The precursor/substrate network region of Sample 2 measured about 170 to 320 microns thick. The wider network thickness range of the compressed sample appears to be related to more of the precursor being fractured and incorporated into the substrate due to compression, resulting in an overall wider cross-sectional area range of the network. Figures 17a and 17b also show that the precursor penetrates relatively evenly across the entire substrate surface. The precursor does not completely penetrate the substrate.

In addition to the above tests, the coating effect on the compressed substrate and the coating effect on the uncompressed substrate were also studied. Figures 18a and 18b show coated substrates prepared as described above, except that the coating was applied to the uncompressed substrate E. The white areas in Figures 18a and 18b are areas where the precursor coating is not well covered. In contrast, Figure 18c shows a coated substrate where the coating was applied to the compressed substrate E. There are no white areas and the blue coating is evenly distributed along the edges to the excluded border. (The images in Figures 18a to 18c were taken through the glass of the glove box and as a result there is some reflection in the images.)

This part of the study shows that compressed coating patches exhibit more disruption in the PEG-based network than uncompressed patches. The compressed coating patches exhibited greater penetration of the precursor into the substrate layer, suggesting that delamination may be reduced (i.e., improved adhesion between the precursor and substrate). Furthermore, the results of this study suggest that pre-coating compression may be used to remove dents and other inconsistencies in the substrate prior to coating, thereby visually improving the coating consistency.

Part C. Patch Testing.

Four coating substrate samples were prepared using the method described in Part B. Two of the samples (Patch Samples 1 and 2) were not pressed. Two samples, Patch Samples 3 and 4, were pressed using a calender roller spaced at 5 mm. In all patch samples, the precursor adhered well to the substrate. There was no evidence of precursor peeling off from the substrate during handling.

Based on these initial observations, each patch sample was cut into 8 mm disk test specimens using an 8 mm biopsy punch and the burst pressure was tested. Table 16 shows the burst pressure results. Patch samples 1 and 2 (uncompressed) and patch samples 3 and 4 (compressed) had similar mean burst pressure results, but the compressed samples had a lower standard deviation of the burst pressure results. These results suggest that compression can improve the consistency of patch performance. The improved consistency may be a result of more collapsed pore structure of the substrate, reduced substrate thickness variability, improved consistency of the precursor/substrate network, increased flexibility/compatibility of the hemostatic patch, and/or improved adhesion of the precursor to the substrate.

Sample Type Patch Sample Psalter Burst pressure, mm Hg Mean burst pressure, mm Hg Standard deviation of burst pressure, mm Hg Uncompressed 1 1 439 518 165 2 407 3 707 2 1 528 451 155 2 272 3 551 Compressed 3 1 568 507 53 2 477 3 477 4 1 580 418 135 2 364 3 611

The results of this study revealed that compressing the cross-linked gelatin substrate while coating with the precursor melt mixture resulted in a consistent, cohesive precursor/substrate network on the upper surface of the substrate. The precursor was adherent to the substrate and did not peel off from the substrate during handling/transportation. The results of this study also showed that compression improved the flexibility/compatibility and performance consistency of the hemostatic patch, with no measurable change in fluid uptake or burst pressure. The results suggest that the compressed hemostatic patch alleviates some of the variability associated with applying the patch to the target surface by manual compression, thereby enhancing adhesion to the target surface and increasing burst strength. The results also suggest that the shear forces generated during compression via calendaring may contribute to the flexibility and performance improvements. The results also suggest that a two-step or multi-step compression process would be advantageous. In particular, the results suggest that an initial compression of the bare substrate is performed to initiate pore destruction/collapse, followed by a secondary compression after coating to further destroy/collapse the pores in the substrate and also destroy the coating.

The above embodiments are illustrative and not limiting. Additional embodiments are included in the claims. Furthermore, while the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that changes in form and detail may be made without departing from the spirit and scope of the invention. The inclusion of such references is intended to limit the incorporation of subject matter that is contrary to the disclosure herein. When specific structures, compositions, and/or processes are described in this specification together with components, elements, ingredients, or other sections, it is to be understood that the disclosure herein includes not only specific embodiments, embodiments that include the specific components, elements, ingredients, other sections, or combinations thereof, but also embodiments that consist essentially of such specific components, elements, ingredients, or other sections, or combinations thereof, which may include additional features that do not change the essential nature of the subject matter as suggested in the discussion, unless specifically indicated otherwise. The term "about" herein means an expected uncertainty of the associated value that a person skilled in the art would understand in a particular context. In relation to a set of ranges for a parameter presented in this specification, this should be interpreted as also explicitly mentioning a related range where the lower limit of one range is combined with the upper limit of another specific range.

Claims (182)

A medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, wherein the dry hydrogel precursor layer comprises an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and a water content of about 2 wt % or less, wherein the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are both substantially non-crosslinked and are mixed with or in direct contact with each other. A medical patch in claim 1, wherein the dry hydrogel precursor layer comprises a mixture of an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor. A medical patch according to claim 1 or 2, wherein the composition lasts for less than 30 days in a physiological solution in a test tube maintained at 37°C. A medical patch according to claim 1 or 2, wherein the composition lasts for less than 2 weeks in a physiological solution in a test tube maintained at 37°C. A medical patch according to any one of claims 1 to 4, wherein the substrate can absorb 300 wt% to 3000 wt% of water. A medical patch according to any one of claims 1 to 5, wherein the substrate comprises gelatin. A medical patch in claim 6, wherein the substrate is partially thermally cross-linked, and the substrate is a foam, a nonwoven tufting material, or a nonwoven felting material. A medical patch according to any one of claims 1 to 7, wherein the dry hydrogel precursor layer comprises multiple layers of a mixture of an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor. A medical patch in claim 8, wherein the dry hydrogel precursor layer is formed from a pure molten mixture of a mixture of an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor. A medical patch according to any one of claims 1 to 7, wherein the dry hydrogel precursor layer comprises a stack of one or more sublayers of an electrophilic hydrogel precursor and one or more sublayers of a nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with each other. A medical patch according to any one of claims 1 to 7, wherein the substrate consists essentially of gelatin, and the dry hydrogel precursor layer consists essentially of a single solid layer comprising an electrophilic hydrogel precursor, a nucleophilic hydrogel precursor, and an optional visualizing agent, wherein the visualizing agent is biocompatible. A medical patch according to any one of claims 1 to 11, wherein the electrophilic hydrogel precursor has a first hydrophilic core comprising a polymer having a molecular weight of about 5000 Da or greater, and the nucleophilic hydrogel precursor has a second hydrophilic core comprising a polymer having a molecular weight of about 2500 Da or greater. A medical patch in claim 12, wherein the first hydrophilic core and the second hydrophilic core independently have a molecular weight of about 10K Da to about 25K Da and 4 to 8 arms. A medical patch in claim 12, wherein the first hydrophilic core and/or the second hydrophilic core comprises polyethylene glycol, polyvinyl alcohol, polyoxazoline, a copolymer thereof or a mixture thereof or another water-soluble medically acceptable polymer having a modifiable functional group, wherein the first hydrophilic core and the second hydrophilic core comprise the same polymer. A medical patch according to any one of claims 1 to 14, wherein the number of arms of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor is independently 3 to 8, and the first hydrophilic core and the second hydrophilic core comprise polyethylene glycol. A medical patch according to any one of claims 1 to 15, wherein the electrophilic hydrogel precursor has an electrophilic functional group comprising an ester. A medical patch in claim 16, wherein the ester is a succinimidyl ester. A medical patch according to any one of claims 1 to 17, wherein the ratio of electrophilic functional groups to protonated amine groups is about 1 or less. A medical patch according to any one of claims 1 to 18, wherein the ratio of the electrophilic functional group to the protonated amine group is approximately 1. A medical patch according to any one of claims 1 to 18, wherein the ratio of electrophilic functional groups to protonated amine groups is from about 0.95 to about 1.05. A medical patch according to any one of claims 1 to 20, wherein the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are each water-soluble. A medical patch according to any one of claims 1 to 21, wherein the medical patch further comprises a therapeutic agent. A medical patch in claim 22, wherein the therapeutic agent comprises an analgesic, an anesthetic, a steroid, an antibiotic, a steroid, an anti-infective, an anti-inflammatory, a non-steroidal anti-inflammatory, an anti-proliferative agent or a combination thereof. A medical patch according to any one of claims 1 to 23, wherein the dry hydrogel precursor layer further comprises a visualizing agent. A medical patch in claim 24, wherein the visualizing agent is biocompatible and comprises a colorant, a fluorescent molecule, a contrast agent or a combination thereof. A medical patch according to claim 24 or 25, wherein the medical patch has a first side comprising a substrate and a second side comprising a dry hydrogel precursor layer and a visualizing agent, wherein the first side is essentially free of the visualizing agent. A medical patch according to any one of claims 1 to 26, wherein the medical patch is flexible and conformable when dried. A medical patch, wherein the patch is rollable for laparoscopic delivery through a trocar, in claim 27. A medical patch according to any one of claims 1 to 28, wherein the medical patch has a thickness of about 0.5 mm to about 5 mm and a width and length independently of about 1 cm to about 15 cm. A medical patch according to any one of claims 1 to 29, wherein the medical patch is free of blood components and human components. A medical patch according to any one of claims 1 to 30, wherein the dry hydrogel precursor layer forms a hydrogel upon contact with a physiological fluid. A medical patch according to any one of claims 1 to 31, wherein the substrate does not adhere to a surgical glove or gauze soaked with a non-buffered solution when dry or wet. A medical patch according to any one of claims 1 to 32, wherein the medical patch has storage stability against severe gelation for at least about one year under refrigerated conditions. A medical patch according to any one of claims 1 to 33, wherein the medical patch is completely absorbed within about 28 days upon contact with a physiological fluid. A medical patch according to any one of claims 1 to 33, wherein the medical patch is completely absorbed within about 9 days upon contact with a physiological fluid. A medical patch according to any one of claims 1 to 35, wherein the medical patch has a three-dimensional contour shape. A medical patch in claim 36, wherein the three-dimensional shape is a standard cone or a truncated cone. A wound filling composition comprising a quantity of shredded material from any one of the patches of claims 1 to 37. A medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, wherein the dry hydrogel precursor layer comprises a PEG-electrophilic hydrogel precursor having a plurality of arms having terminal reactive electrophilic groups and a PEG-nucleophilic hydrogel precursor having a plurality of arms having terminal protonated amine groups, and wherein the water content is about 2 wt % or less, wherein both the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor are substantially uncrosslinked, and wherein the dry hydrogel precursor layer forms a crosslinked hydrogel within 5 minutes upon hydration with a physiological solution. A medical patch in accordance with claim 39, wherein the substrate is biodegradable, comprises gelatin, and is partially thermally cross-linked, wherein the substrate is a foam, a nonwoven tufting material, or a nonwoven felting material, and wherein the medical patch persists for less than 2 weeks in a physiological solution in a test tube maintained at 37°C. A medical patch according to claim 39 or 40, wherein the dry hydrogel precursor layer comprises a plurality of layers of a mixture of a PEG-electrophilic hydrogel precursor and a PEG-nucleophilic hydrogel precursor or a stack of one or more sub-layers of a PEG-electrophilic hydrogel precursor and one or more sub-layers of a PEG-nucleophilic hydrogel precursor, wherein adjacent sub-layers are in direct contact with one another, wherein the medical patch has a width and a length independently of about 1 cm to about 15 cm and a thickness of about 0.5 mm to about 5 mm. A medical patch according to any one of claims 39 to 41, wherein the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor independently have a molecular weight of about 10K Da to about 25K Da and 4 to 8 arms, and wherein the reactive electrophilic groups comprise an ester. A wound filling composition comprising a predetermined amount of finely chopped material from a patch according to any one of claims 39 to 42. A method for forming a medical patch, comprising:
A method comprising the step of applying one or more liquid layers to a porous hydrophilic substrate in a dry atmosphere to form a hydrogel precursor layer on the porous hydrophilic substrate, wherein the hydrogel precursor layer comprises a mixture of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, or a stack of sublayers of each of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with one another, and wherein the protected nucleophilic hydrogel precursor comprises an acidified amine, and wherein the liquid comprises the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor, and wherein the liquid comprises a melt or a non-aqueous solution of the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor. A method according to claim 44, wherein the temperature of the liquid is about 95°C or lower. A method according to claim 44 or 45, further comprising a step of drying the porous hydrophilic substrate prior to application. A method in claim 46, wherein drying is performed until the moisture content of the porous hydrophilic substrate becomes about 2 wt% or less. A method according to any one of claims 44 to 47, wherein the application comprises slot die coating, doctor blading, jetting or spraying. A medical patch according to any one of claims 44 to 48, wherein the thickness of the medical patch is about 5 mm or less. A method according to any one of claims 44 to 49, further comprising the step of sterilizing the medical patch with radiation. A method according to any one of claims 44 to 50, further comprising the step of forming the medical patch into a three-dimensional contour shape after applying one or more liquid layers. As a method of using a medical patch,
A method comprising the steps of disposing one or more medical patches on or within a bleeding defect associated with an organ, wherein the medical patch comprises a biocompatible substrate and an initially dried substantially non-crosslinked hydrogel precursor layer on the substrate, wherein the layer comprises an electrophilic hydrogel precursor and a nucleophilic precursor as a mixture or as multiple stacked sublayers in direct contact with one another. A method according to claim 52, wherein one or more medical patches are provided in a disposable pharmaceutical packaging having high moisture barrier properties and/or a desiccant. A method according to claim 52 or 53, further comprising the step of forming an outline of one or more medical patches so as to have a three-dimensional shape corresponding to the interior of the bleeding defect. A method according to any one of claims 52 to 54, wherein the organ is an interface with a bone, a gland, a digestive organ, a pulmonary organ, a urinary organ, a reproductive organ, a blood vessel, a natural or synthetic graft, or a combination thereof. A method according to any one of claims 52 to 55, wherein the bleeding defect is a suture line, a puncture wound, a gunshot wound, a hole, a depression, a biopsy punch hole, a graft interface, or a combination thereof. A method according to any one of claims 52 to 56, wherein the dispensing is performed without pre-wetting one or more of the medical patches. A method according to any one of claims 52 to 57, further comprising the step of wetting one or more of the medical patches with unbuffered water or unbuffered saline solution prior to and/or after the disposition. A method according to any one of claims 52 to 58, wherein the disposition comprises disposing one or more medical patches on a bleeding defect having an uneven topography. A method according to any one of claims 52 to 59, wherein the disposition comprises wrapping one or more medical patches around the organ. A method according to claim 60, wherein the organ is an artery or a vein, and the organ is natural, transplanted, or a combination thereof. A method according to any one of claims 52 to 59, wherein the disposition comprises directing a medical patch onto or into a bleeding defect using a tubular applicator, wherein the medical patch has a three-dimensional contoured shape. In claim 62, the tubular applicator has a shape that is coupled with the three-dimensional shape of the medical patch. A method in claim 62, wherein the tubular applicator has a conical distal end and the three-dimensional shape of the medical patch is a cone, wherein the placement comprises directing the medical patch through the vagina toward the cervix using the tubular applicator. A method according to any one of claims 52 to 64, wherein the disposition comprises disposing one or more first medical patches on the bleeding defect and then disposing one or more second medical patches so as to overlap at least a portion of the one or more first medical patches. A method according to any one of claims 52 to 65, wherein the dispensing further comprises manually applying pressure to the one or more medical patches for up to about 2 minutes. A method according to any one of claims 52 to 66, wherein the placement results in hemostasis within about 5 minutes. In claim 67, the method wherein the bleeding defect has an Adam's score of 1 to 4. A method according to any one of claims 52 to 68, wherein the layer forms a hydrogel within about 2 minutes upon contact with a physiological fluid associated with the organ, and the hydrogel adheres to the organ. A method according to any one of claims 52 to 69, wherein the at least one medical patch has a width and a length independently of about 1 cm to about 15 cm, and wherein an edge of the at least one medical patch is attached to the organ within about 5 minutes after placement. A method according to any one of claims 52 to 70, wherein the bleeding defect comprises blood treated with an anticoagulant. A method according to any one of claims 52 to 71, wherein the one or more medical patches are completely absorbed within about 28 days. A method according to any one of claims 52 to 72, wherein the one or more medical patches remain at least partially attached to the organ until the one or more medical patches are essentially completely absorbed. A method according to any one of claims 52 to 73, wherein the at least one medical patch has a gelation time of less than or equal to about 5 minutes at 37° C., wherein the gelation time is measured in vitro using a texture analyzer to generate a force versus time plot immediately after activating the patch with a buffer solution of pH 8, wherein the gelation time is the time corresponding to the lowest force in the plot. A method according to any one of claims 52 to 74, wherein at least one patch has a burst pressure of at least about 50 mm Hg. A granular composition comprising a mixture of a porous hydrophilic material and a hydrogel precursor, wherein the hydrogel precursor comprises an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and wherein the water content is about 2 wt % or less, wherein both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially non-crosslinked and are present in the same granule or separate granules, or a combination thereof. A granular composition in claim 76, wherein the porous hydrophilic material and the hydrogel precursor form a complex within the granules. A granular composition in claim 76, wherein the porous hydrophilic material and the electrophilic hydrogel precursor or the nucleophilic hydrogel precursor form a complex within the granule. A granular composition in claim 76, wherein the complex of the porous hydrophilic material and the hydrogel precursor exists as separate granules. A granular composition in claim 76, wherein the porous hydrophilic material, the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are present as separate granules. In claim 76, a granular composition wherein the porous hydrophilic material, the electrophilic hydrogel precursor, the nucleophilic hydrogel precursor, or the mixture of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor at least partially coats the porous hydrophilic material. A granular composition according to any one of claims 76 to 81, comprising 10 to 75 wt% of a porous hydrophilic material, wherein the ratio of electrophilic functional groups to protonated amine groups is approximately 1. A granular composition according to any one of claims 76 to 82, wherein the porous hydrophilic material comprises two or more materials. A granular composition according to any one of claims 76 to 83, comprising granules having an average diameter of about 0.001 mm to about 2 mm. A granular composition comprising a powder according to any one of claims 76 to 84. A granular composition according to any one of claims 76 to 85, further comprising a visualizing agent and/or a therapeutic agent. A method using the granular composition of any one of claims 76 to 86,
A method comprising the step of placing a granular composition on or within a bleeding defect. A medical patch comprising a biocompatible substrate and a hydrogel precursor exhibiting a surface along one side of the biocompatible substrate, wherein the hydrogel precursor comprises an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of nucleophilic functional groups, wherein the biocompatible substrate comprises thermally cross-linked gelatin, wherein the hydrogel precursor extends at least partially into the surface of the biocompatible substrate to form a cohesive hydrogel precursor structure, wherein the cohesive hydrogel precursor structure comprises a mixture layer of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor and/or separate adjacent layers, wherein the medical patch exhibits a shattered surface of the cohesive hydrogel precursor structure adhered to the biocompatible substrate. A medical patch in claim 88, wherein the biocompatible substrate comprises a foamed gelatin material. A medical patch in claim 89, wherein the foamed gelatin material comprises gelatin felt. A medical patch in claim 88, wherein the biocompatible substrate consists essentially of foamed gelatin having a disrupted cell structure. A medical patch according to any one of claims 88 to 91, wherein the biocompatible substrate is capable of absorbing 100% to 2500% by weight of water based on the dry patch weight. A medical patch according to any one of claims 88 to 92, wherein the biocompatible substrate does not adhere to a surgical glove or gauze soaked with a non-buffered solution when dry or wet. A medical patch according to any one of claims 88 to 93, wherein both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially non-crosslinked. A medical patch according to any one of claims 88 to 94, wherein the cohesive hydrogel precursor structure comprises a stack of multiple layers of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor in direct contact with each other. A medical patch according to any one of claims 88 to 94, wherein the cohesive hydrogel precursor structure comprises a mixture layer. A medical patch according to any one of claims 88 to 96, wherein the cohesive hydrogel precursor structure does not contain a buffer or a non-aqueous solvent. A medical patch according to any one of claims 88 to 97, wherein the medical patch has a thickness of about 0.25 mm to about 10 mm when dry and a width and length independently of about 1 cm to about 15 cm. A medical patch according to any one of claims 88 to 98, wherein the cohesive hydrogel precursor structure has a surface that essentially matches a surface of the biocompatible substrate. A medical patch according to any one of claims 88 to 99, wherein the medical patch is sufficiently flexible to be wound around a ½ inch mandrel without breaking when dry. A medical patch according to any one of claims 88 to 100, wherein the medical patch has an accordion-folded shape. A medical patch according to any one of claims 88 to 101, wherein the patch is capable of being rolled or folded without breaking for laparoscopic delivery through a trocar. A medical patch according to any one of claims 88 to 102, wherein the cohesive hydrogel precursor structure crosslinks to form a cohesive hydrogel structure within about 30 seconds upon exposure to a physiological fluid or a physiological buffered saline solution. A medical patch according to any one of claims 88 to 103, wherein the cohesive hydrogel precursor structure spontaneously crosslinks upon exposure to a physiological fluid or a physiological buffered saline solution to form a cohesive hydrogel structure. A medical patch according to any one of claims 88 to 104, wherein the broken surface comprises a plurality of microfractures and/or cracks created by the compression manufacturing step. A medical patch according to any one of claims 88 to 105, wherein the nucleophilic hydrogel precursor comprises a plurality of protonated amine groups. A medical patch according to any one of claims 88 to 106, wherein the electrophilic hydrogel precursor has a first hydrophilic core comprising a polymer having a molecular weight of about 5000 Da or greater, the nucleophilic hydrogel precursor has a second hydrophilic core comprising a polymer having a molecular weight of about 2500 Da or greater, and wherein each of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor is water-soluble. A medical patch in claim 107, wherein the first hydrophilic core and the second hydrophilic core independently have a molecular weight of about 5K Da to about 35K Da and 4 to 8 arms, and wherein the first hydrophilic core and the second hydrophilic core comprise polyethylene glycol, polyoxazoline or a copolymer thereof. A medical patch according to any one of claims 88 to 108, wherein the electrophilic hydrogel precursor has an electrophilic functional group comprising a succinimidyl ester. A medical patch according to any one of claims 88 to 109, wherein the medical patch further comprises a therapeutic agent. A medical patch according to any one of claims 88 to 109, wherein the therapeutic agent comprises an analgesic, an anesthetic, a steroid, an antibiotic, a steroid, an anti-infective, an anti-inflammatory, a non-steroidal anti-inflammatory agent, an antiproliferative agent or a combination thereof. A medical patch according to any one of claims 88 to 111, wherein the cohesive hydrogel precursor structure further comprises a visualizing agent. A medical patch in claim 112, wherein the visualizing agent is biocompatible and comprises a colorant, a contrast agent, or a combination thereof. A medical patch according to any one of claims 88 to 113, wherein the medical patch has a storage stability against severe gelation of at least about 2 months when stored dry. A medical patch according to any one of claims 88 to 114, wherein the medical patch has a storage stability against severe gelation for at least about one year under refrigerated conditions. A medical patch according to any one of claims 88 to 115, wherein the medical patch is provided in a moisture-proof packaging material. A medical patch according to any one of claims 88 to 116, wherein the medical patch is completely absorbed within about 9 days upon contact with a physiological fluid. A medical patch according to any one of claims 88 to 117, having a burst pressure of at least about 150 mm Hg. A method of using a flexible medical patch,
A method comprising the steps of: disposing one or more flexible medical patches on or within a target bleeding site, wherein the flexible medical patch comprises a biocompatible substrate and a hydrogel precursor defining a surface along one side of the biocompatible substrate, wherein the hydrogel precursor comprises an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor as a mixture or in multiple stacked regions in direct contact with each other, wherein the biocompatible substrate has a disrupted cell structure, wherein the hydrogel precursor is initially dried and substantially non-crosslinked and at least partially expands into the disrupted cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure, wherein the medical patch is hemostatically adhered to the target bleeding site. A medical patch in claim 119, wherein the biocompatible substrate comprises thermally cross-linked gelatin. A method according to claim 119 or claim 120, wherein the dispensing is performed without pre-wetting one or more flexible medical patches. A method according to any one of claims 119 to 121, wherein the placement comprises placing one or more flexible medical patches on a target bleeding site having an uneven terrain. A method according to any one of claims 119 to 122, wherein the disposition comprises wrapping one or more flexible medical patches around a bodily structure, wherein the bodily structure comprises a target bleeding site. A method according to any one of claims 119 to 123, wherein the target bleeding site is associated with an artery and/or a vein, wherein the artery and/or vein are natural, grafted, or a combination thereof. A method according to any one of claims 119 to 124, wherein the method further comprises the step of bending or folding the one or more flexible medical patches into a three-dimensional shape prior to deployment. A medical patch in claim 125, wherein the three-dimensional shape comprises an accordion fold. A method according to claim 125, wherein the bending or folding is performed without pre-wetting one or more flexible medical patches. A method according to any one of claims 119 to 127, wherein the disposition comprises directing one or more flexible medical patches onto or into the bleeding defect site via a tubular applicator. A medical patch, wherein the tubular applicator comprises a cannula, in claim 128. A method according to claim 128 or claim 129, wherein the target bleeding site is associated with a laparoscopic surgical site. A method according to any one of claims 119 to 130, wherein the dispensing further comprises manually applying pressure to the one or more flexible medical patches for up to about 30 seconds. A method according to any one of claims 119 to 131, wherein the placement results in hemostasis within about 3 minutes. A method according to any one of claims 119 to 132, wherein the target bleeding site has an Adam's score of 1 to 4 and/or a SPOT GRADE® score of 1 to 5. A method according to any one of claims 119 to 133, wherein the cohesive hydrogel precursor structure forms a cohesive hydrogel structure within about 30 seconds upon contact with a physiological fluid associated with the target bleeding site, and the cohesive hydrogel structure adheres to the target bleeding site. A method according to any one of claims 119 to 134, wherein the target bleeding defect is blood that has been treated with an anticoagulant. A method according to any one of claims 119 to 135, wherein the one or more flexible medical patches are completely absorbed within about 28 days. A method according to any one of claims 119 to 136, wherein the one or more flexible medical patches are completely absorbed within about 7 days. A method according to any one of claims 119 to 137, wherein the one or more flexible medical patches remain at least partially adhered to the target bleeding site until the one or more flexible medical patches are essentially completely absorbed. A medical patch comprising a biocompatible substrate and a hydrogel precursor, wherein the hydrogel precursor comprises a solid mixture and/or separate solid layers of an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of nucleophilic functional groups, wherein both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially non-crosslinked, the biocompatible substrate comprises thermally crosslinked gelatin having a disrupted cell structure, and wherein the hydrogel precursor at least partially extends into the disrupted cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure. A medical patch in claim 139, wherein the biocompatible substrate comprises a foamed gelatin material, a nonwoven tufted gelatin material, or a nonwoven felted gelatin material. A medical patch according to claim 139 or 140, wherein the biocompatible substrate comprises a gelatin sponge or gelatin felt capable of absorbing 100% to 2500% by weight of water based on the dry patch weight. A medical patch in claim 139, wherein the biocompatible substrate consists essentially of expanded gelatin and a hydrogel precursor. A medical patch according to any one of claims 139 to 142, wherein the thickness of the biocompatible substrate is from about 0.2 mm to about 8 mm when the medical patch is dried. A medical patch according to any one of claims 139 to 143, wherein the medical patch further comprises a therapeutic agent. A medical patch in claim 144, wherein the therapeutic agent comprises an analgesic, an anesthetic, a steroid, an antibiotic, a steroid, an anti-infective, an anti-inflammatory, a non-steroidal anti-inflammatory, an anti-proliferative agent or a combination thereof. A medical patch according to any one of claims 139 to 145, wherein the medical patch further comprises a visualizing agent. A medical patch according to any one of claims 139 to 146, wherein the cohesive hydrogel precursor structure has a surface that essentially conforms to a surface of the biocompatible substrate. A medical patch according to any one of claims 139 to 147, wherein the hydrogel precursor exhibits a surface on one side of the biocompatible substrate and has no surface on the opposite side of the biocompatible substrate. A medical patch according to any one of claims 139 to 148, wherein the medical patch is sufficiently flexible to be wound around a ½ inch mandrel without breaking when dry. A medical patch according to any one of claims 139 to 149, wherein the medical patch has a three-dimensionally folded shape. A medical patch according to any one of claims 139 to 150, wherein the medical patch has an accordion-folded shape. A medical patch according to any one of claims 139 to 151, wherein the patch is capable of being rolled or folded without breaking for laparoscopic delivery through a trocar. A medical patch according to any one of claims 139 to 152, wherein the cohesive hydrogel precursor structure crosslinks within about 30 seconds upon exposure to a physiological fluid or a physiological buffered saline solution. A medical patch according to any one of claims 139 to 153, wherein the cohesive hydrogel precursor structure spontaneously crosslinks upon exposure to a physiological fluid or a physiologically buffered saline solution. A medical patch according to any one of claims 139 to 154, wherein the medical patch exhibits a broken surface of a cohesive hydrogel precursor structure that adheres to a biocompatible substrate when dried, wherein the broken surface comprises a plurality of microfractures and/or cracks. A medical patch according to any one of claims 139 to 155, wherein the nucleophilic hydrogel precursor comprises a plurality of protonated amine groups. A medical patch according to any one of claims 139 to 156, wherein the electrophilic hydrogel precursor comprises polyethylene glycol, polyoxazoline or a copolymer thereof having a molecular weight of about 10K Da to about 35K Da and 3 to 8 arms terminated with succinimidyl ester functional groups, and the nucleophilic hydrogel precursor comprises polyethylene glycol, polyoxazoline or a copolymer thereof having a molecular weight of about 10K Da to about 35K Da and 3 to 8 arms terminated with protonated amine functional groups. A medical patch in claim 157, wherein the succinimidyl ester functional group comprises N-hydroxy succinimidyl succinate (SS), N-hydroxy sulfosuccinimidyl succinate, N-hydroxy sulfosuccinimidyl glutarate, succinimidyl glutarate (SG), succinimidyl adipate (SAP), succinimidyl azelate (SAZ) or a mixture thereof. A method for forming a medical patch, comprising:
A method comprising the steps of forming a medical patch by compressing a structure comprising a biocompatible substrate and a hydrogel precursor layer or layers coated on the substrate from a melt, the structure exhibiting a surface along one side of the biocompatible substrate, wherein the biocompatible substrate comprises expanded gelatin having a disrupted cell structure, and the hydrogel precursor layer or layers at least partially extend into the disrupted cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure, wherein when wetted with a physiological fluid or a physiological buffered saline solution, the cohesive hydrogel precursor structure is crosslinked to form a cohesive hydrogel structure. A method in claim 159, wherein the compression comprises calendering the structure. A method in claim 160, wherein calendaring is performed using a calendar roller having a gap of about 5% to about 70% of the structure thickness. A method according to any one of claims 159 to 161, wherein the hydrogel precursor layer or layers are at room temperature during compression. A method according to any one of claims 159 to 162, wherein the compression fractures the surface of the cohesive hydrogel precursor structure to form a fractured surface that adheres to the biocompatible substrate. A method according to any one of claims 159 to 163, wherein the medical patch is more flexible and hydrates more quickly than its pre-compressed structure. A method according to any one of claims 159 to 164, wherein the medical patch is sufficiently flexible to be wound around a ½ inch mandrel without breaking when dry. A method according to any one of claims 159 to 165, further comprising, prior to compressing the biocompatible substrate to form a layer or layers of hydrogel precursors coated on the substrate, a step of coating the biocompatible substrate with a layer or layers of hydrogel precursors, wherein the coating comprises melt coating a dry mixture of an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of nucleophilic functional groups. In claim 166, the biocompatible substrate is sufficiently flexible to be wound around a ½ inch mandrel without breaking prior to coating. A method according to claim 166, further comprising the step of initially compressing the biocompatible substrate prior to coating. A method in claim 168, wherein the initial compression comprises calendering the biocompatible substrate. In claim 169, the method is performed using a calendar roller having a gap of about 5% to about 65% of the thickness of the biocompatible substrate. A method in claim 168, wherein compressing the biocompatible substrate causes destruction of the cell structure of the expanded gelatin. A method according to any one of claims 159 to 171, wherein the foamed gelatin is heat cross-linked. A method according to any one of claims 168 to 171, further comprising the step of heat crosslinking the biocompatible substrate prior to the initial compression. A method for forming a medical patch, comprising:
A method comprising: applying a liquid hydrogel precursor to a porous hydrophilic substrate in a dry atmosphere; wherein the applying is performed by a print head compressing the substrate at a printing location to inject the liquid hydrogel precursor into the compressed substrate;
A method wherein the liquid hydrogel precursor comprises an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, the protected nucleophilic hydrogel precursor comprises an acidified amine, and the liquid hydrogel precursor comprises a melt or non-aqueous solution of the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor. A method according to claim 174, wherein the porous hydrophilic substrate comprises thermally cross-linked gelatin. A method according to claim 174 or 175, wherein the application is performed by compressing the substrate to a selected depth with a print head. A method in claim 176, wherein the selected depth is from about 5% to about 30% of the thickness of the porous hydrophilic substrate prior to application. A method according to any one of claims 174 to 177, wherein the liquid hydrogel precursor comprises a mixture of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor. A method according to any one of claims 174 to 178, wherein the liquid hydrogel precursor comprises a first melt of an electrophilic hydrogel precursor and a second melt of a nucleophilic hydrogel precursor, and wherein applying comprises applying the first melt followed by applying the second melt or applying the second melt followed by applying the first melt. A method according to any one of claims 174 to 179, further comprising the step of calendering the porous hydrophilic substrate prior to applying. A method according to any one of claims 174 to 180, further comprising the step of calendaring the medical patch after application. In claim 181, the calendering comprises a first calendering and a second calendering, wherein the first calendering is performed with a calender roller having a first gap and the second calendering is performed with a calender roller having a second gap, the second gap being smaller than the first gap.