CN119212741A

CN119212741A - Water-activated hydrogel-based medical patches, flexible substrates, and methods of making and using such patches

Info

Publication number: CN119212741A
Application number: CN202380038586.8A
Authority: CN
Inventors: 迈克尔·巴西特; D·T·乐; 戴维·朱斯蒂
Original assignee: Pramand LLC
Current assignee: Pramand LLC
Priority date: 2022-05-06
Filing date: 2023-05-04
Publication date: 2024-12-27
Also published as: JP2025515177A; EP4518920A1; AU2023265069A1; WO2023215453A1; KR20250008770A

Abstract

The medical patch may include a biocompatible substrate and a dried hydrogel precursor layer on the substrate, the dried hydrogel precursor layer including an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and no more than about 2% by weight water. Both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked and blended or in direct contact with each other. The medical patch may be formed by coating a melt blend of hydrogel precursors, or a dry nonaqueous solvent-based solution, onto a porous hydrophilic substrate, such as a compressed gelatin substrate, in a dry environment. The flexible medical patch may be formed by a process that includes compression coating a substrate, such as with calendaring. The medical patch may be used for placement on bleeding wounds or the like, and may be used as a hemostatic patch.

Description

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

Cross Reference to Related Applications

This PCT application claims priority from commonly-owned U.S. patent application Ser. No. 17/738,847 entitled "Water activated hydrogel-based medical Patch and methods of making and using such Patches," filed 5/6 of Bassett et al 2022, and U.S. patent application Ser. No. 18/142,956 entitled "Water activated hydrogel-based medical Patch, flexible substrate, and methods of making and using such Patches," filed 3/5 of Bassett et al 2023, 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 to control bleeding, surgical occlusion, promote healing, and for topical drug delivery. The invention also relates to a method of making the patch, such as forming a melt blend that is cast onto a suitable substrate. The flexible substrate allows for the delivery of folded patches for placement in otherwise inaccessible locations.

Background

Hydrogels have found a range of uses in medical applications for surgical closure, drug delivery, tissue fillers, spacers, and the like. In the case of wound healing, the hydrogel material may provide a hydrophilic environment to isolate tissue and promote healing. For hemostatic and other wound healing applications, existing products have limitations that limit their effective use.

Disclosure of Invention

In a first aspect, the present invention is directed to a medical patch comprising a biocompatible substrate and a dried hydrogel precursor layer on the substrate, the dried hydrogel precursor layer comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and no more than about 2% by weight water. Typically, both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked and blended or in direct contact with each other.

In another aspect, the present invention is directed to a medical patch comprising a biocompatible substrate and a dried hydrogel precursor layer on the substrate, the dried hydrogel precursor layer comprising a PEG-electrophilic hydrogel precursor having a plurality of arms with terminal reactive electrophilic groups and a PEG-nucleophilic hydrogel precursor having a plurality of arms with terminal protonated amine groups, and no more than about 2 wt% water. Typically, both the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor are substantially uncrosslinked, and the dried hydrogel precursor layer forms a crosslinked hydrogel no more than 5 minutes after hydration with a physiological solution.

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

Applying one or more layers of liquid 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 blend of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, or a stack of sub-layers of the electrophilic hydrogel precursor and the protected nucleophilic hydrogel precursor, respectively, wherein adjacent sub-layers are in direct contact with each other. The protected nucleophilic hydrogel precursor comprises an acidified amine and the liquid comprises an electrophilic hydrogel precursor and/or a protected nucleophilic hydrogel precursor. The liquid comprises a melt or non-aqueous solution of the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor.

In other aspects, the invention relates to a method for using a medical patch, the method comprising:

placing one or more medical patches on or in an organ-related bleeding defect, wherein the medical patches comprise a biocompatible substrate and an initially dried, substantially uncrosslinked hydrogel precursor layer on the substrate, wherein the layer comprises an electrophilic hydrogel precursor and a nucleophilic precursor as a blend or in the form of a plurality of stacked sublayers in direct contact with each other.

In a further aspect, the present invention relates to a particulate composition comprising a blend of a porous hydrophilic material and a hydrogel precursor comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and no more than about 2 wt% water. Typically, both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked and are in the same particle, or in different particles, or a combination thereof. The granular composition may be placed in a bleeding defect where it undergoes gelation.

In another aspect, the present invention is directed to a medical patch comprising a biocompatible substrate and a hydrogel precursor presenting 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 crosslinked gelatin. The hydrogel precursor extends at least partially into the surface of the biocompatible substrate to form an adhesive hydrogel precursor structure. The adhesive hydrogel precursor structure includes a blended layer and/or a separate adjacent layer of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor, and the medical patch presents a fragmented surface of the adhesive hydrogel precursor.

In another aspect, the invention relates to a method for forming a medical patch, the method comprising compressing a structure comprising a biocompatible substrate and one or more hydrogel precursor layers to form a medical patch, the one or more hydrogel precursor layers being coated from a melt onto the substrate, presenting a surface along one side of the biocompatible substrate, wherein the biocompatible substrate comprises foamed gelatin having a ruptured cell structure. One or more hydrogel precursor layers extend at least partially into the ruptured cell structure of the biocompatible substrate to form an adhesive hydrogel precursor structure, wherein upon wetting with a physiological fluid or physiological buffered saline, the adhesive hydrogel precursor structure crosslinks to form an adhesive hydrogel structure.

In a further aspect, the present invention relates to a method for using a flexible medical patch comprising placing one or more flexible medical patches on or in a target bleeding site, wherein the flexible medical patch comprises a biocompatible substrate and a hydrogel precursor presenting a surface along one side of the biocompatible substrate. The hydrogel precursor includes an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor as a blend and/or in the form of a plurality of stacked regions in direct contact with each other, and the biocompatible substrate has a broken cell structure. Typically, the hydrogel precursor is initially dry and substantially uncrosslinked and extends at least partially into the ruptured cell structure of the biocompatible substrate to form an adhesive hydrogel precursor structure in which the medical patch is hemostatic adhered to the targeted bleeding site.

In a further aspect, the present invention relates to a method for forming a medical patch comprising applying a liquid hydrogel precursor to a porous hydrophilic substrate in a dry atmosphere, wherein the applying is performed by compressing the substrate at a print location using a print head 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, wherein 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 comprising a solid blend and/or a separate solid layer 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 uncrosslinked. The biocompatible substrate comprises thermally crosslinked gelatin having a ruptured cell structure wherein the hydrogel precursor extends at least partially into the ruptured cell structure of the biocompatible substrate to form an adhesive hydrogel precursor structure.

Drawings

Fig. 1A is a perspective view of a hemostatic patch structure.

Fig. 1B is a perspective view of a layered hemostatic patch structure.

Fig. 1C is a perspective view of a hemostatic patch structure having a compressed base.

Fig. 1D is a perspective view of a hemostatic patch structure having a compressed substrate and an adhesive hydrogel precursor network with a fractured surface.

Fig. 2 is a perspective view of an apparatus for spraying a blended precursor composition onto a substrate to produce a hemostatic patch.

Fig. 3A is a side view of an apparatus for slot die coating a blended precursor composition onto a substrate to make a hemostatic patch.

Fig. 3B is a side view of an apparatus for slot die coating similar to the apparatus in fig. 3A, wherein the coating head is adjusted to press into the substrate during coating.

Fig. 4A is a side view of an apparatus for continuous roll-slot die coating of blended precursor composition onto a substrate to produce a hemostatic patch.

Fig. 4B is a flow chart of a two-step compression process according to an embodiment of the present disclosure.

Fig. 4C is a side view of a process flow for manufacturing a flexible hemostatic patch product from a gelatin sheet and a hydrogel precursor composition.

Fig. 4D is a side view of the gap between the calender rolls.

Fig. 5 is a schematic view of a hemostatic patch wrapped around a tubular organ.

Fig. 6 is a schematic view of a hemostatic patch disposed over a non-tubular organ.

Fig. 7 is a schematic view of a hemostatic patch placed on the skin.

Fig. 8A is a cross-sectional view of a bleeding defect of tissue.

Fig. 8B is a cross-sectional view of the hemostatic patch after placement over the bleeding defect of fig. 8A.

Fig. 8C is a cross-sectional view of the hemostatic patch of fig. 8B adhered to a bleeding defect.

Fig. 8D is a cross-sectional view of the healed tissue after absorption of the hemostatic patch.

Fig. 9 is a schematic of Adam scale for defect bleeding scoring.

Fig. 10A is a photograph of an initial placement of a patch into a channel defect.

Fig. 10B is a photograph of fig. 10A 1 minute after placement.

Fig. 11 is a graph of force versus time for a representative patch sample evaluated using a commercial texture analyzer.

Fig. 12A is a schematic view of the placement of a tapered hemostatic patch into the cervix using a tapered mandrel.

Fig. 12B is a schematic view of a tapered hemostatic patch placed in a cervix, with the left inset showing the tapered mandrel pressing the patch into the cervix and the right inset showing the tapered mandrel removed and the tapered patch remaining in the cervix. In the left illustration, only the tapered end of the mandrel is shown, the handle of the tapered mandrel is not shown.

Fig. 13A is a perspective view of an accordion folded flexible hemostatic patch.

Fig. 13B is a schematic view of the use of forceps to introduce an accordion folded flexible hemostatic patch into a cannula.

Fig. 13C is a schematic view of an accordion-like and laterally folded flexible hemostatic patch.

Fig. 13D is a schematic view of the use of forceps to introduce an accordion-like and laterally folded flexible hemostatic patch into a cannula.

Fig. 14 is a schematic view of the use of forceps to introduce an accordion folded flexible hemostatic patch into a laparoscopic surgical site.

Fig. 15A is an SEM image of a cross-linked gelatin substrate.

Fig. 15B is an SEM image of the cross-linked gelatin substrate of fig. 15A after calendering.

Fig. 15C is an SEM image of a cross-linked gelatin substrate.

Fig. 15D is an SEM image of the cross-linked gelatin substrate of fig. 15C after calendering.

Fig. 16A is an SEM image of the surface of the precursor coated gelatin substrate.

Fig. 16B is an SEM image of the surface of the precursor coated gelatin substrate after compression with calender rolls set to a 5mm gap.

Fig. 16C is an SEM image of the surface of the precursor coated gelatin substrate after compression with calender rolls set to a 2mm gap.

Fig. 16D is an SEM image of the surface of the gelatin substrate coated with precursor after first compression with a calender roll set to a 5mm gap and second compression with a calender roll set to a 2mm gap.

Fig. 17A is an SEM image of a cross-section of a precursor coated gelatin substrate.

Fig. 17B is an SEM image of a cross-section of the precursor-coated gelatin substrate of fig. 17A after calendering.

Fig. 18A is a first photograph of a precursor coated substrate, wherein the substrate was not compressed prior to coating.

Fig. 18B is a second photograph of a precursor coated substrate, wherein the substrate was not compressed prior to coating.

Fig. 18C is a photograph of a precursor coated substrate, wherein the substrate was calendered prior to coating.

Fig. 19 is a graph of average fluid absorption over time for an uncompressed substrate and a compressed substrate.

Detailed Description

The medical patch is formed as a dried layer with a hydrogel precursor on a substrate, either as a blend or as an adjacent sub-layer in direct contact, wherein upon hydration with a biological fluid, spontaneous crosslinking results to form a hydrogel that can adhere to tissue. Generally, the hydrogel precursors need not react with blood or tissue, as any physiological fluid can activate crosslinks that involve an equal or near equal amount of reaction of nucleophilic and electrophilic functional groups. The process of forming the hydrogel precursor layer is generally selected to avoid substantial crosslinking during processing by protecting the nucleophilic groups and avoiding moisture (even if the reactive species are in contact). Processing may include forming a dehydrated melt blend of precursors, which may then be coated or cast to form the layer, or by coating a non-aqueous solution of the blend and removing the solvent. The substrate supporting the dried hydrogel may be selected to be absorbent such that the substrate further assists in the hemostatic function of the patch. Furthermore, the processing of the patch and the deposition of the hydrogel precursor can be designed to obtain a flexible patch, wherein the hydrogel precursor material has good adhesion to the substrate and the hydrogel precursor material has good adhesion (cohesion), which in the finished patch presents a surface for adhering to a wound. Placement of the patch on difficult to reach locations and/or abnormally shaped wounds may be accomplished through the use of flexible and biodegradable substrates. Contact with the tissue during the crosslinking process may promote the formation of the desired adhesive bonds, whether or not any covalent bonding occurs with the tissue, and whether or not blood is present. With the selected components, the patches may be folded without fracturing so that they may be delivered and/or folded through a trocar for insertion into a wound rather than over the wound during laparoscopic surgery. The increased flexibility of the patch may be achieved by appropriate choice of substrate, and the ideal patch may include compressed gelatin sponge, together with an appropriately integrated precursor layer that penetrates into the compressed sponge. Surprisingly good adhesion of the hydrogel precursor layer to the surface provides bonding along the edges of the patch without direct contact with blood or the wound. The results of these patches show that the material is also obviously useful as a filler for wounds and the like, which may be formed from a shredded patch (crushed patch) or equivalently formed material, wherein the components are shredded, crushed or otherwise disintegrated individually.

Gelatin substrates can provide desirable fluid absorption and biodegradation over a suitable time frame. In particular, the foamed gelatin meets these characteristics, although other porous gelatin forms may have similar characteristics, such as fused fiber gelatin. However, it has been found that a higher degree of flexibility is required than is directly obtainable with these materials. Compressing the substrate before and/or after deposition of the precursor material (such as using calendaring) may be desirable to impart a significantly higher degree of flexibility. In the case of porous gelatin substrates, the precursor material, as a blend of precursors and/or as separate precursors, is coated onto the surface of the substrate to provide a blended layer and/or separate adjacent layers of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor. It is desirable for the coated substrate to be both flexible and mechanically strong in terms of the bond strength of the blended layer and/or the individual adjacent layers and the adhesion strength to the substrate so that the precursor does not delaminate or flake from the dried patch. It has been found that injecting the hydrogel precursor (as one or more melts or one or more non-aqueous solutions) onto a substrate under slight compression results in improved adhesion of the hydrogel precursor to the porous substrate while maintaining good adhesion of the hydrogel precursor. Although the elasticity of the substrate may result in restoration of the thickness of the substrate after deposition of the hydrogel precursor, deposition of the hydrogel precursor into the substrate with good permeability provides good adhesion of the hydrogel precursor to the substrate while still presenting the surface of the hydrogel precursor on most or all of the surface to establish adhesion of the patch to the tissue surface during use. After deposition of the hydrogel precursor, the structure may be compressed (such as by calendaring) to further improve the flexibility of the patch, which may fracture the surface of the precursor. The resulting patch structure can have the desired flexibility while maintaining good adhesion and adhesiveness of the hydrogel precursor, so that delamination or peeling of the hydrogel precursor can be avoided. The hydrogel precursor has some characteristics of the surface layer, but the hydrogel precursor also at least partially penetrates into the substrate and thus has some characteristics of the integrated structure. The adhesive hydrogel precursor structure may adhere to the substrate via a diffusion boundary between the hydrogel precursor and the substrate. Since the substrate surface is microscopically not smooth, gelatin whiskers from the substrate can penetrate into the hydrogel precursor present along the substrate surface and the hydrogel precursor can penetrate into and embed into a portion of the substrate to form a diffusion boundary between the hydrogel precursor and the substrate within the cohesive hydrogel precursor structure. In various cases, the hydrogel precursor may alternatively be described as one or more layers, or coatings, or as exhibiting an adhesive hydrogel precursor structure (or an adhesive hydrogel precursor network) of the hydrogel precursor surface. Although the clear boundary may not separate the substrate and the hydrogel precursor, the hydrogel precursor still presents a surface along the substrate such that the patch is capable of adhering to wet tissue upon hydration of the hydrogel precursor.

The dried layer of hydrogel precursors (such as a blend) typically includes 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, nucleophilic amines can be protonated to form cationic ammonium groups, which protect the amine from nucleophilic reactions until it is deprotonated. Halides (such as chlorides) or other strong acid conjugated anions may be counter ions. Once the blend is hydrated and the ammonium groups are deprotonated due to dilution of the acid upon hydration, the electrophilic and nucleophilic functional groups can react to form covalent crosslinks. Thus, in the patch product, the hydrogel precursor is substantially uncrosslinked, as described further below. In some embodiments, the patch or portion thereof may be degradable. The precursors may be applied as different layers or as a pre-mixed melt. If a melt is chosen, it is advantageous to use the melting point of the blend precursor so that it remains solid at room temperature, thereby providing maximum storage stability. The precursor blend may comprise components that are liquid at room temperature, but the blend has a melting point above room temperature. In principle, the precursor blend may be a viscous liquid at room temperature, but the resulting patch may then require refrigerated storage to ensure storage stability. The patch may be used for implantable applications or for exposed tissue or skin tissue healing. The substrate may be selected accordingly. The patch may be effectively used for hemostatic applications. For hemostatic applications, absorbent substrates are highly desirable. The absorbent substrate may be formed from natural materials such as collagen, gelatin, cellulose or other similar biopolymers, or from synthetic hydrogels such as polymers including polyethylene glycol, polyvinyl alcohol or other water-soluble or water-swellable synthetic polymers, or combinations with biopolymers. Substrates that are flexible and provide good drape properties typically provide desirable patch properties, or substrates that soften rapidly when exposed to moisture and become drapeable may also provide desirable properties for many applications.

In some embodiments, the precursor layer does not have added buffer, and the results clearly demonstrate rapid and good gelation without any buffer. Some suitably selected buffer may be present without disrupting the function of the precursor layer. In this case, inorganic buffers may be desirable because they may remain in separate phases until activated by the physiological fluid. Carbon dioxide from the air or carbon dioxide present in the laparoscopic environment may dissolve into the water to form carbonic acid, which may provide a small amount of buffering capacity. The carbonic acid evaporates in the form of carbon dioxide rather than concentrating as the water is removed. An improperly selected buffer may be undesirable because it results in undesirable premature crosslinking of the precursor prior to use or results in reduced crosslinking after application to tissue. Although water is removed from the patch during processing, trace amounts of water may still cause some crosslinking if a higher pH buffer is present, and more acidic buffers may slow crosslinking upon contact with physiological solutions (typically having a slightly alkaline pH). Based on experience with these polymer systems, phosphate buffers and perhaps other neutral to weakly acidic buffers can be used, typically with moderate slowing of gelation. There is evidence that patches without buffering agents can provide desirable properties along with adequate storage stability. Patches without significant addition of buffer or with acceptable levels of buffer may be more readily described from the point of view of patch function, such as storage stability and gelation rate, as described in detail below. If buffers are included, they may be placed on the substrate, for example as a powder, with the hydrogel precursor layer over them, or if they are compatible with the non-aqueous form of the precursor layer, they are blended into the hydrogel precursor layer.

Various suitable substrates are described below. Gelatin-based sponge patches have been found to have particularly effective patch properties. Improved flexibility can be obtained using these sponges as substrates if the sponges are compressed to disrupt the cell structure of the sponges. While the compression of the gelatin cell structure reduces the mechanical strength of the substrate, the substrate correspondingly becomes significantly more flexible while maintaining sufficient mechanical stability for application of the hydrogel precursor layer to the substrate and application of the patch. While various processing schemes can be effectively used, a two-step compression process produces particularly desirable results. The hydrogel precursor layer may be added after the first compression and before the subsequent compression. The hydrogel precursor penetrates into the broken cell structure of the sponge to stabilize the patch, and the hydrogel precursor layer breaks during further compression, which not only improves the flexibility of the coated substrate, but also promotes and accelerates the hydration of the precursor layer to accelerate the adhesion effect.

As described in more detail below and clearly exemplified, the patch has very good adhesion to wet tissues. Efficient manufacturing methods are described. Hydrogels are designed to have approximately equal amounts of electrophilic and nucleophilic functional groups so that complete crosslinking can occur, and complete crosslinking is expected to occur between hydrogel precursors, without any of the precursors having to be bonded to functional groups in the blood or tissue. Based on the teachings of the art, strong adhesion of the patch in the absence of covalent bonds to blood or tissue is a surprising result. This improved design provides excellent properties including, for example, strong adhesion and rapid gelation while maintaining good shelf life. If it is desired to accelerate the gelation time, a buffer/accelerator solution may be applied shortly after the patch is applied to the tissue (such as through the backing) to further accelerate the gelation process. Although in principle the buffer/accelerator solution may be added to the patch immediately before application to the tissue, this approach may result in gelling too fast to achieve good adhesion.

The patch is particularly suitable for sealing active leaks or bleeding. In the case of liquid precursors, such blocking is generally not possible only when delivered as a spray sealer, because the precursor is replaced by active fluid outflow. In the case of patch-based sealants as subject of the present invention, manual compression, which is applied as part of patch application, can temporarily control active fluid outflow and cause the sealant to activate and adhere to the tissue surface, thereby forming an effective seal.

For some wounds, such as those that may have cavities and bleeding is less severe, inserting a patch material may be effective in stabilizing the wound, where the material is crosslinked in place. Medical personnel may shred the patch by themselves for use, or may dispense the shredded patch material in that form. In order to make a crushed patch composition, the patch need not be fully formed to produce a similar material. A substrate, such as a gelatin substrate, may be chopped and a precursor blend may be formed and crushed/reduced to fine particles. For example, the melt blend or solution may be spray dried/cooled to directly form the particulate material, which may be further ground or sieved if desired. The individual shredded/crushed materials may then be mixed for distribution and use. While forming a precursor blend for comminution may be desirable for rapid gelation/crosslinking, separate precursor powders may be blended as an alternative. The relative amounts of the components may follow the ranges described for the patch, although slightly varying amounts may be selected for commercialization of these embodiments based on clinical experience.

The particulate composition may be prepared from a crushed patch that is a blend of a porous hydrophilic material and a hydrogel precursor, wherein the porous hydrophilic material is the substrate of the patch and the hydrogel precursor is a dried layer of the hydrogel precursor on the substrate. The blend may be homogeneous or heterogeneous. In some embodiments, the particulate composition is a blend in which the porous hydrophilic material and the hydrogel precursor have separate sources. For example, the porous hydrophilic material may be a crushed 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 may be a foam, a nonwoven tufted material, or a nonwoven felted material. Two or more porous hydrophilic materials may be used together. Examples of different hydrophilic porous materials include, for example, substrates of the same material but with different porosities, pore sizes, and/or particle sizes, or substrates of different compositions. The hydrogel precursor may be provided as a blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor in the same particles, or as different particles of the electrophilic hydrogel precursor and different particles of the nucleophilic hydrogel precursor, or as a combination thereof. In some embodiments, the weight ratio of crushed substrate/porous hydrophilic material in the crushed patch composition may be from about 5 weight percent (wt%) to about 75 wt%, in some embodiments from about 7 wt% to about 50 wt%, and in other embodiments from about 10 wt% to about 35 wt%. In other embodiments, the crushed substrate may be less than 25%, less than 10% by weight. In other embodiments, the particulate composition of the precursor may be used without any crushed substrate such that the crushed patch weight ratio is 0 wt%. Those of ordinary skill in the art will recognize that additional ranges of porous hydrophilic material compositions within the explicit ranges above are contemplated and are within the present disclosure.

The particulate composition may have particles composed of any combination of porous hydrophilic material and hydrogel precursor. The particles of different compositions may have different average particle diameters from each other. In one embodiment, the porous hydrophilic material and the hydrogel precursor form an intra-particulate composite. In another embodiment, the porous hydrophilic material and the electrophilic hydrogel precursor form a composite material within the particle, and the nucleophilic hydrogel precursor is in separate/distinct particles. In another embodiment, the porous hydrophilic material and the nucleophilic hydrogel precursor form a composite material within the particle, and the electrophilic hydrogel precursor is in separate/distinct particles. In another embodiment, the porous hydrophilic material is in particles and the composite of hydrogel precursors is in separate/distinct particles. In another embodiment, the porous hydrophilic material, the electrophilic hydrogel precursor, and the nucleophilic hydrogel precursor are in separate/distinct particles. The particle composition may be provided as particles of a porous hydrophilic material coated or at least partially coated with one or both of an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor. The coating of the one or more precursors may be accomplished by spraying a melt or solution of the one or more precursors. Multiple layers of coatings may be applied, such as layers of one precursor over layers of a different precursor.

The particulate composition may have particles ranging in form from powder to small particles to coarse pieces, such as particles obtained by chopping a substrate or patch. The small particles may have an average diameter of about 0.001mm to about 5mm or about 0.01mm to about 3.5 mm. The particles may or may not be approximately spherical and may be of any reasonable shape. The particulate composition may also contain imaging and/or therapeutic agents, as described for the patch. The granular composition may be placed on or in a bleeding defect, and pressure may optionally be applied. The bleeding defect may be partially or completely filled with the granular composition or thinly coated with the granular composition. Those of ordinary skill in the art will recognize that additional ranges of average diameters within the explicit ranges above are contemplated and are within the present disclosure. If the patch is shredded by medical personnel for use, the resulting patch fragments can generally have substantial size and shape variations as desired by medical personnel.

Due to the ability to mix the precursors thoroughly, rapid gel formation is possible even if the amine is initially protected. Once the acid protecting groups are neutralized after dilution with physiological solution, crosslinking begins. The physiological solution is typically weakly alkaline and has a physiological pH (e.g., plasma) in the range of 7.32 to 7.42pH units. For the PEG-NH ₂ group, the-NH ₃ ⁺ moiety should be deprotonated to form a nucleophilic active form, even at neutral water pH. Thus, with proper hydration, the patch can gel in less than one minute, and the examples demonstrate rapid gelation. Due to the chemistry used, the patch typically adheres to any moist tissue surface with physiological solution and does not need to be in direct contact with blood and/or the wound, although it may be present. Patches are designed for quick and predictable efficacy, which can significantly aid in performing effective medical procedures.

Each precursor composition may be selected to form a non-decomposing, thermally flowable composition, which may be blended as a liquid. The thermally flowable composition or blend of two or more thermally flowable compositions may be a neat melt or neat melt blend, respectively, where "neat" refers to a liquid phase composition without the addition of solvent. The melt blend may then be coated onto a substrate and cooled to form a patch. In particular, precursors having polyethylene glycol cores typically form flowable liquids at relatively low temperatures. Slit coating, extrusion, screen printing, or other suitable coating processes may be used to form the coated substrate. In some embodiments, the precursor may be dissolved in some organic solvent in which the precursor is suitably stable, such as an aprotic polar solvent. The solution of the mixed precursor may be coated onto a substrate (such as spray coating) and dried to remove the solvent. In alternative embodiments, the precursor may be treated with a non-aqueous solvent solution, wherein the solvent is selected to avoid deprotonation of the acidifying amine group. The precursor solution may be deposited using techniques similar to precursor melts.

Medical patches may be of great value in closing wounds in a patient (as part of surgery) or along the skin for wound healing or surgical closure or other various uses. The patch of the present invention provides significant advantages for activation by any physiological fluid such that 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 may form an effective seal, even along edges that may not be in direct contact with blood or tissue. For example, the absorbent substrate may absorb the physiological fluid and wet portions of the patch with the physiological fluid along the entire patch surface. And if there is adequate moisture, no portion of the patch needs to be in direct contact with blood or tissue for adhesion, so, for example, lymph may effectively activate the patch by direct contact or transfer from the substrate. The patch may be used for human or veterinary medical purposes. The patch can be prepared without blood component and human body component.

The patch may generally have a base layer and a hydrogel precursor layer on the base layer, wherein the precursor layer may be a blend of precursors and/or sub-layers of the same and/or different composition. The base layer may be homogenous or it may have a structure of multiple and/or structured layers. Typically, the base layer is dry when the patch is formed, and the base layer is formed of biodegradable material, although for some applications it may be desirable to use a non-degradable base. The substrate may be very absorbent, which may help manage blood and other fluids while the hydrogel seals the wound. Patches are typically of sufficient thickness to provide the required mechanical integrity, but are not too thick, and patches of an appropriate thickness can provide the required crosslinking and hydration over the required period of time, and degrade over the appropriate time and are not too bulky.

The precursor may be selected to be flowable using thermal processing to form a flowable state at an appropriate temperature. For embodiments in which the precursors are blended in a flowable state during processing, the formation of the melt blend should be thermally stable for each precursor. Processing may be performed in a low humidity environment so that the hygroscopic material does not absorb unwanted moisture from the air. In general, the flow characteristics of the heated precursor composition are strongly affected by the polymer core flanked by functional groups. In particular, polyethylene glycol-based precursors have the advantage of relatively low flow temperatures and receiving batches of implantable medical products, although other hydrophilic precursor cores may be used.

In some embodiments, the precursor may be blended in an organic solution if the precursor is soluble in a suitable organic solvent that does not cause cross-linking. Various solution coating techniques may be suitable for forming the precursor coating from the solution blend. After the coating is formed, the organic solvent may be removed by evaporation to form a dried coating. After drying, the patch may be packaged in a waterproof bag or the like similarly to the patch formed by cooling the melt.

In order to achieve the desired shelf life, proper handling and processing characteristics, and settings at the time of application, the amine precursors are provided in the form of acid salts/conjugates, and the blended precursors may be free of buffers, or only have a suitable choice of buffers, which do not unduly slow gelation or destabilize the patch in storage. The presence of an alkaline pH buffer may tend to amplify the instability by potentially removing protons from the amine to cross-linking during processing. Although water is avoided during synthesis, it is not possible to obtain extremely low water content for all hydrophilic components. On the other hand, the amine is selected to be easily deprotonated upon contact with physiological fluids, such that no buffer is required to achieve rapid gelation.

Other hemostatic hydrogel patches are known. For example, fibrin-based patches are available on the market.Is a fibrin based patch from Baxter. Similar powders and syringes based on fibrin are also available to deliver a matrix or other blood-based component. Another method of the patch involves partially crosslinking the hydrogel in the patch to leave unreacted electrophilic groups. The partial cross-linking provides a hydrogel precursor layer for solution processing to make patches, where the precursor intentionally has a ratio of functional groups that creates a large number of unreacted electrophilic groups (insufficient nucleophile). Unreacted electrophilic groups are intended to react with nucleophilic groups (such as naturally occurring amines) in blood or tissue at a wound site. The disadvantage of this approach is that the patch only adheres to the tissue or blood, thus away from the patch edge where direct wound interaction may occur, and where direct contact with the blood or tissue may not occur, possibly resulting in partial patch adhesion and/or poor patch adhesion. Hydrogels based on this approach have been described using polyoxazoline copolymers as cores for functionalized precursors. See published U.S. patent application 2019/023293 to Hoogenboom et al, entitled "crosslinked Polymers and implants derived from electrophilically activated polyoxazolines" (Cross-Linked Polymers AND IMPLANTS DERIVED From Electrophilically Activated Polyoxazoline), incorporated herein by reference. These polyoxazoline-based crosslinked polymers are described as adhesives and are not explicitly described as hydrogels. In contrast, hydrogels described herein originate from the occurrence of all or substantially all of their crosslinking after application, and do not rely on reactions with tissue or blood or other nucleophiles provided by the patent to do so, although some reactions of the precursors of the invention with blood or tissue may occur. Even though the hydrogel precursors of the present patches react only effectively with themselves, they still achieve excellent adhesion.

Hemostatic patches based on polyethylene glycol (PEG-based) are sold under the trade name Veriset ^TM (Medtronic). It is believed that Veriset ^TM relates to the technique described in published U.S. patent application 2010/0100123A (' 123 application) titled "hemostatic implant (Hemostatic Implant)" to Bennett, which is incorporated herein by reference. These patches involve separate precursor components. In contrast, the methods herein involve blended or strongly contacted hydrogel precursor components that can rapidly form a highly crosslinked homogeneous hydrogel in contact with a patient. Due to the mixing or intimate contact of the uncrosslinked precursors, the hydrogels can gel rapidly to form homogeneous hydrogels with good mechanical stability, good adhesion, and predictable properties. Another hemostatic patch is sold by Baxter International, inc (IL, USA) under the name HEMOPATCH ^TM with a PEG-based NHS hydrogel precursor. The precursor coating in HEMOPATCH is intended to crosslink with amines in tissue and blood.

Generally, applicants' patch herein includes a substrate and a hydrogel precursor layer. The cross-linking of the hydrogel precursor layer after placement on the tissue site serves to adhere the patch to the site. The substrate is typically adhered to the precursor layer and may be used to promote hydration and stabilization of the patch in use, especially in the case of hemostasis. For this reason, the substrate is typically highly absorbent and porous while maintaining mechanical integrity. In this way, the substrate may absorb fluid (such as blood) to help stabilize the site of the patch and to help hydrate the hydrogel to drive crosslinking, while not being so porous that blood passing through the substrate adheres the substrate surface, such as to gauze or a surgeon's glove. The substrate absorbency can be assessed in terms of swelling, and the substrate can form a hydrogel, but the hydrogel does not exhibit further crosslinking upon hydration. The porosity of the substrate typically allows penetration of the hydrogel precursor into some of the adjacent substrate surfaces.

In the hydrogel precursor layer of the patch of the present invention, the two precursors for crosslinking may be mixed in a dehydrated state or formed as a sub-layer within the precursor layer. The amine groups are in a protonated acidic state. The precursor layer may be effectively free of buffer to support relatively more rapid crosslinking upon hydration with physiological fluids. The precursor layer is stable under dry storage for a suitable period of time for product dispensing with commercially suitable shelf life. Of course, the precursor may contain trace amounts of anionic contaminants, but a suitably pure precursor should eliminate any quality issues. One or more amine end group precursors may be used, and one or more precursors reactive with nucleophilic end groups may also be used to form the patches described herein.

The crosslinking reaction involves reacting the nucleophilic amine with an appropriate group to effect an addition reaction. The addition reaction is typically carried out at a reasonable rate at higher pH values (typically pH 7 or higher). Without the use of an activating solution, deprotonation of the amine can occur relatively quickly after hydration with a physiological solution, then allowing the crosslinking reaction to occur in a short period of time (e.g., <3 minutes). The results in the examples demonstrate rapid gelation. Because the precursors are mixed or intimately contacted in the dry patch, the reactive crosslinking groups can be in the vicinity without extensive movement of the macromolecular precursor molecules involved in crosslinking. As described and exemplified below, the initially uncrosslinked precursor can rapidly gel to induce adhesion of the patch. In general, high pH buffers are not required to induce gelation at an appropriate rate, and such high pH buffers (such as borate buffers) may facilitate reduced storage times. Low pH buffers (such as phosphate-based buffers) typically extend the gelation time, but suitable amounts of these buffers may not slow gelation in unacceptable amounts. Low pH buffers may not adversely alter storage time. If desired, additional external higher pH buffers may be applied to the patch after placement of the patch on the patient for a particular application, but this is not required.

The substrate used to support the hydrogel precursor may be absorbent, which may provide several advantages. First, it can absorb fluids (such as blood, lymph, etc.) so that it can help healthcare professionals manage wounds when the patch is applied. In addition, absorption of physiological fluids by the absorbent substrate can assist in hydration of the hydrogel precursor. Thus, the absorbent substrate may accelerate the gel time, which may be less than one minute. The substrate is typically biodegradable, although in some embodiments, the substrate may be non-degradable over a relevant time frame, such as in some applications involving external applications of the patch. In the case of external use patches, the backing substrate may not be biodegradable and the patch may be removed after healing is complete, or the hydrogel formed from the precursors in contact with the tissue may be absorbable to release the patch substrate after a few days. In certain cases, it may be advantageous to deliver the hydrogel itself, and in such cases a non-porous backing substrate may be used so that it can release the hydrogel onto wet tissue without adhering to the hydrogel itself. In such applications, substrates made from polymeric substrates (such as polytetrafluoroethylene, polyethylene, polyurethane, etc.) that exhibit low adhesion to the hydrogel precursor may be useful. A release layer of an adhesive bandage or the like may be suitable for this purpose.

For most hemostatic applications of patches, it is desirable that the substrate be biodegradable to non-toxic breakdown products in a reasonable period of time for removal from the patient. The substrate may desirably absorb body fluids and engage the osmotic precursor layer. While various natural and man-made materials (typically polymers) can provide these properties, gelatin sponge materials have been found to perform particularly well in patch constructions. To achieve the desired level of flexibility, the gelatin sponge may be compressed to disrupt the gelatin cell structure and the precursor layer may penetrate into the disrupted cell structure to form a complete and stable structure with the desired absorption characteristics.

Gelatin is a hydrolysate of collagen, which is a major component of the extracellular matrix of animals. Collagen is typically harvested from a variety of livestock animals. Collagen is insoluble fibrin in its natural form. Hydrolysis breaks down the protein polymer chains into smaller units so that the resulting gelatin can be processed. The exact nature of gelatin may depend on the process. But in general gelatin is soluble in hot water and some other polar solvents. To restore gelatin to insoluble, gelatin may be crosslinked to control specific properties. To avoid crosslinking using toxic chemicals, sufficient crosslinking can be achieved by heating. To form the absorbent substrate, the gelatin is formed as a sponge having a cell type structure. The foamed gelatin cell structure may be formed without cross-linking.

The formation of gelatin sponges is known and is then generally stabilised by chemical cross-linking. See, for example, published U.S. patent application 2007/007774 (the' 274 application) entitled "method for producing shaped bodies based on crosslinked gelatin (Method for Producing Shaped Bodies Based on Crosslinked Gelatin)", of Ahlers, which is incorporated herein by reference. The' 274 patent relates to previous crosslinked gelatin products that are not sufficiently continuous for certain applications. Crosslinked gelatin is formed using a pore former, such as air, to provide a sponge structure with pores. The product of the' 274 patent is still biodegradable. Gelatin sponges are commercially available for use as hemostatic materials. For example, gelatin sponges are available from Gelita AG (Germany, applicant of the' 274 patent) and Ethicon (U.S.). Uncrosslinked gelatin sponge can be obtained. Gelita and Ethicon sell gelatin sponges as hemostatic patches, i.e(Ethicon) and(Gelita)。

While chemical crosslinking may be desirable for longer durations, chemical crosslinking may involve the use of toxic chemicals or other moieties that may be undesirable in terms of biodegradation of the material and may result in the material being too durable. Chemical crosslinking may also alter the mechanical properties of the substrate, making it more brittle. On the other hand, completely uncrosslinked gelatin may decompose too quickly before hemostasis is achieved and thus result in loss of absorbency of body fluids. Thermal crosslinking can achieve the desired balance of properties without the need to introduce chemicals that can complicate biocompatibility. As described in the' 274 patent, thermal crosslinking of gelatin may result in dehydration, which may form crosslinks. Thermal crosslinking is described further below.

Previous work has shown that compressing gelatin sponges can increase flexibility. The' 274 application discusses "mechanical action," including passing through rollers to increase the flexibility of the crosslinked gelatin sponge. They suggest an increase in density by a factor of 2 to 10, but do not describe the mechanical properties of the material after mechanical action, except that the reference suggests that dissolution over time is not affected and no data is provided. DeAnglis et al, entitled "Flexible gelatin sealant dressing with reactive Components" (Flexible GELATIN SEALANT DRESSING WITH REACTIVE Components) ", describe the use of compressed gelatin substrates with hydrogel precursors (the' 157 application). The' 157 application mentions that gelatin is preferably compressed after crosslinking. Accordingly, the '157 application mentions that the compressed gelatin sponge is stronger due to the higher crosslink density (caused by the closer physical proximity of the amine groups of the protein), although 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 a previously published U.S. patent application that teaches the association of hydrogel precursors with an absorbent substrate, see U.S. patent application 2011/0045047 to Bennett et al entitled "hemostatic implant (Hemostatic Implant)", which is incorporated herein by reference, which appears to be a subsequent work to the above-referenced' 123 application. The' 157 application points out an undesirable aspect of the earlier work and is directed to an alternative to using dry precursor powders deposited on porous substrates.

The' 157 application exemplifies the use of commercial substrate materials, particularlyProduct codes 1974 and 1975 (which are said to be compressed), andAnd (5) a gelatin film. The' 157 application does not describe the detailed nature of these substrates and does not undergo any particular further processing prior to application of the hydrogel precursor. As described above, the precursor was added as a fine dry powder, which was a blend 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 applied in the form of a suspension using an organic solvent, which is then evaporated. The powder precursor lacks the advantages of the solid precursor layer described herein.

It is believed that commercial gelatin sponges for hemostatic purposes are typically chemically crosslinked, for example with aldehydes (such as formaldehyde or glutaraldehyde), to stabilize the structure for reasonable duration in contact with biological fluids. As described above, the' 157 application uses commercial substrates from Ethicon, inc. With no detailed information regarding substrate production or specific characteristics other than size. As described herein, processing involves a coating process to form a continuous precursor layer that is designed to be stable and uncrosslinked until activated by body fluid or water. The precursor layer then exhibits a synergistic relationship with the substrate, wherein the precursor layer can stabilize the substrate and penetration of the hydrogel precursor into the substrate can stabilize the hydrogel precursor from delamination or exfoliation.

In applicants' process, compression of the patch structure is performed after application of the hydrogel precursor layer. This compression step typically breaks or breaks the formed precursor layer, thereby forming microcracks and/or cracks, etc. across the surface. Microcracks and/or crazes are consistent with the increased flexibility of the resulting patch. The hydrated patch becomes adhered to tissue whether or not 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 the improvement of the mechanical properties of the patch is considered to be greater if the patch material is less elastic, such that compression results in a greater reduction in thickness along with less rebound after compression. The cell structure of the gelatin sponge then breaks, which may further promote hydration and improve flexibility. In addition to compression after placement of the precursor layer, the gelatin patch may also be compressed prior to application of the precursor layer. The initial compression may facilitate penetration of the precursor layer into the gelatin while maintaining the surface of the precursor layer.

In order to improve the adhesion of the hydrogel precursor to the porous gelatin substrate, it has been found that the hydrogel precursor can be deposited onto the substrate in a slightly compressed state. The print head may be adjusted to provide a desired deposition configuration. The porous gelatin substrate may have some elasticity, so moderate compression during the hydrogel precursor layer may not result in a continuous change in substrate thickness. However, deposition onto the substrate under compressive force appears to result in a greater degree of penetration of the hydrogel precursor into the substrate. The resulting patch structure exhibits a desired degree of hydrogel precursor adhesion and cohesiveness, thereby reducing or eliminating any flaking or delamination of the hydrogel precursor from the dried patch. The resulting hydrogel precursor structure presents a surface for application to a wound, wherein the surface is completely or at least significantly covered, even if broken, by the hydrogel precursor. The hydrogel precursor structure may be referred to as one or more layers, or expressed in terms reflecting its penetration into a substrate to form an adhesive hydrogel precursor or coating having a more complex structure, such as an adhesive hydrogel precursor structure, an adhesive hydrogel precursor network, or an adhesive network, which are used interchangeably herein.

In principle, the compression of the gelatin sponge can be performed in various ways, such as placing a patch between two plates and fastening it to the structure. One convenient way to apply compression is to pass the patch through calender rolls. The spacing of the calender rolls may be set to achieve the desired compression. The use of rollers for compression is also convenient from the point of view of the process flow method and the application of shear forces to break the precursor layer. The roller may be repeatedly applied to gradually achieve the desired compression. The first compression without the precursor layer may be performed at a larger roll spacing than later through the roll with the precursor layer.

For hydrogel precursor layers, the protected nucleophilic precursor typically has an acidifying amine group. For example, the amine may be reacted with a strong acid (such as hydrochloric acid) and the chloride ion or other corresponding conjugate base may remain associated with the precursor. Acidification of the amine stabilizes the precursor layer by inhibiting the crosslinking reaction until the amine can be deprotonated. By this precursor selection, the resulting patch can be stable for a considerable period of time in dry storage. Nucleophilic precursors typically have multiple functional groups, and three or more groups may allow for more highly crosslinked structures. The nucleophilic precursor may have a hydrophilic core, which may be highly branched and have pendant amine groups. The low pH buffer may not destabilize the acidifying amine group.

Electrophilic precursors have electrophilic groups that can undergo addition reactions with amines to form covalent crosslinks. Electrophilic groups typically react only with amine groups and do not react with protonated amine groups, ammonium acid conjugates. The electrophilic precursor has a plurality of functional groups, and can form a highly crosslinked hydrogel with three or more functional groups. Electrophilic groups are typically pendant from a hydrophilic core (such as polyethylene glycol), which may be appropriately branched to form the desired degree of crosslinking.

The electrophilic precursor and the protected nucleophilic precursor may be designed to have a flow temperature below the decomposition temperature of either precursor. Thus, a melt blend can be formed with both compounds. The melt blend may be formed into a good mixture. The melt blend may then be processed to form a patch. If the precursor layer comprises sub-layers, these sub-layers may be applied sequentially on top of each other. The sub-layer may comprise a blend of precursors or one of the precursors. In general, processing can be performed under low humidity conditions to reduce any moisture absorption from the surrounding atmosphere. The melt blend may be formed directly into a coating for a patch, although the melt blend may in principle be solidified for subsequent processing. For example, the melt blend may be slot coated onto the substrate, although other processing techniques such as extrusion, screen printing, spraying, and the like may be used. Slit coating or other coating techniques may be performed on the substrate sheet for efficient processing. After the coating has cured, the coated sheet can be cut to the desired patch size. Alternatively, a coating may be formed on the precut patch substrate. The patch may be dispensed using a suitable package to maintain the dehydrated state.

In some embodiments, the precursor may be soluble in an inert organic solvent. Suitable solvents may be aromatic liquids such as toluene, xylene, dimethyl carbonate, and the like, or aprotic solvents. In general, the solution can be highly concentrated to reduce solvent use, so long as the fluid properties allow for proper processing. The coating method used for solvent-based deposition may generally be the same as that used for melt blending, and the concentration may be appropriately adjusted according to the particular deposition method.

The components of the patch tend to be hydrophilic and/or hygroscopic. Thus, the synthesized or purchased components may be dried/dehydrated prior to processing to form a patch. Some substrates may be lyophilized. In some embodiments, it may be desirable to achieve a hydration level of no more than 5% by weight or significantly lower. The processing may be performed in a controlled atmosphere of dry air, nitrogen, etc., with the application of heat and vacuum. Processing may include purging techniques that employ a limited flow of inert drying gas in conjunction with heat under partial vacuum to enhance drying. Conditions for reducing moisture can be provided. After the patch is formed, it can be packaged in moisture-proof packaging under dry air. The patch may be sterilized, for example, using ethylene oxide gas during packaging or using radiation after packaging. Sterilization may be performed without causing substantial cross-linking.

The hydrogel patches described herein are particularly suitable for use as implantable hemostatic patches that may be absorbed over a reasonable period of time ranging from days to a month or more. Hydrogel patches may be used to control bleeding or to close wounds for open or laparoscopic surgery. Hydrogel patches may generally be used for any wound healing event, including superficial placement, rather than implanted placement. The characteristics of rapid closure, good adhesion and adjustable absorption time provide desirable characteristics for a range of applications.

Patch structures and hydrogel precursors

The hydrogel precursor patches described herein generally include a substrate and a hydrogel precursor layer (as a blend or sub-layer) on the surface of the substrate, although typically with some penetration into the substrate. The substrate may be selected to be suitable for the desired patch application. Typically, the substrate is absorbent and the substrate can be absorbed in situ within a reasonable period of time of contact with the patient. The patch may be adapted for implantation in a patient, and for these embodiments, the substrate is generally absorbable. The precursor is typically substantially uncrosslinked and blended within the layer. The layer may be uniform over the substrate or may be variable. The precursors are selected to crosslink relatively rapidly upon exposure to physiological solutions or tissues. The patch may be suitable for use as a hemostatic patch that helps control and limit bleeding.

In the patch before use, the hydrogel precursors in the layer on the substrate are substantially uncrosslinked. Accurate quantization may be impractical, but the explicit meaning of the concept and satisfaction of these conditions is very clear. First, the chemical design is such that crosslinking is not expected, as the amine groups are protected by acid modification to block nucleophilic reactions. Significant crosslinking results in the attachment of various precursor molecules into a network structure. At some degree of crosslinking, the material no longer has independent precursor molecules and essentially becomes a cohesive body of material joined together by covalent bonds. This process is evaluated in the case of gelation, and the bond may be referred to as the resulting gel, which in this case is a hydrogel. As the degree of cross-linking of the hydrogel precursor increases over time beyond gelation and toward complete cross-linking, the gel becomes stronger and firmer. For example, as described below, the gelation time (or gelation time) may be measured. In contrast, at an intermediate time before gelation, as some crosslinking occurs, the properties change, which changes the behavior of the composition. If the precursor is substantially uncrosslinked, the properties of the fully hydrated precursor do not change significantly and the flow properties and rheology of the precursor composition do not change measurably relative to the uncrosslinked composition formed, although these properties can change rapidly once crosslinking is allowed to begin.

Fig. 1A shows 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 may be a gelatin substrate or other suitable substrate as described below. For example, the substrate 102 may be a gelatin substrate to which no blood components (such as fibrinogen or thrombin or platelets) are added. In some embodiments, the substrate 102 is porous and absorbent. In additional or alternative embodiments, the substrate 102 is biodegradable. Typically, the substrate is relatively thin, such as having an average thickness of no more than one centimeter, and the area of the patch may be appropriately selected depending on the particular application.

The precursor layer 104 may be a blend of an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor. Alternatively or additionally, the precursor layer 104 may be configured as a sub-layer of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor, which may or may not include a blend, but generally has an interface of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor along the sub-layer. In some embodiments, the sub-layer applied to the substrate in liquid form forms a single homogenous layer on the substrate after cooling and/or drying. In other embodiments, the sublayers form a continuous layer with a composition gradient. Fig. 1B shows an alternative structure of a hemostatic patch. Hemostatic patch 150 has a substrate 152 and a precursor layer 154. Precursor layer 154 is configured as a stack of sublayers 160 and 164. Sublayers 160 and 164 are in direct contact with each other. In some embodiments, sublayer 160 is a sublayer of the electrophilic hydrogel precursor and sublayer 164 is a sublayer of the nucleophilic hydrogel precursor. In other embodiments, the composition of the sublayers is reversed and sublayer 160 is a sublayer of the nucleophilic hydrogel precursor and sublayer 164 is a sublayer of the electrophilic hydrogel precursor. In some embodiments, precursor layer 154 is configured as three or more alternating sublayers, such as sublayer 160/sublayer 164/sublayer 160, wherein adjacent sublayers are in direct contact with each other. As used throughout this document, direct contact between hydrogel precursors means that it involves not only accidental or unintentional contact of substantial surface areas of the respective components along the layer expansion dimension, and typically this will involve layer-by-layer interactions. The multiple sublayers may have the same thickness or different thicknesses. In some embodiments, the precursor layer 104/154 has an imaging agent such 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 coloration due to the presence of the dye.

Fig. 1C shows another configuration of a hemostatic patch. The hemostatic patch 170 has a compressed base 172 and a precursor layer 174. Typically, the compression substrate 172 is porous and absorbent. In some embodiments, the precursor layer 174 penetrates into the porous structure of the compression substrate 172. Precursor layer 174 can be prepared from the same compositions as described above for precursor layer 104 and/or precursor layer 154 or have the same sublayer structure as it. In some embodiments, the precursor layer 174 has cracks, such as microcracks and/or crazes. Fig. 1D shows another configuration of a hemostatic patch. The hemostatic patch 180 has a compression substrate 182 and an adhesive hydrogel precursor structure 184 having a fracture surface 186. Typically, the adhesive hydrogel precursor structure 184 has a precursor material embedded in a substrate material while presenting a surface on one side of the compression substrate 182. In some embodiments, the surface area of the compression substrate 182 associated with the cementitious hydrogel precursor network 184 is fully coated with the hydrogel precursor blend. Typically, the compression substrate 182 is porous and absorbent. Generally, the hydrogel precursors have good adhesion within the cohesive hydrogel precursor structure 184, thereby resisting fragmentation and loss of precursor material even if the surface breaks up. Generally, the hydrogel precursors within the cohesive hydrogel precursor structures 184 have good adhesion to the compression substrate 182. In some embodiments, good adhesion and/or good cohesion may be characterized by the cohesive hydrogel precursor structure 184 being resistant to flaking during handling and/or further processing. The treatment and/or further processing may include calendaring, such as to cause disruption of the surface 186 of the adhesive hydrogel precursor structure 184, and the treatment after the patch is formed involves, for example, bending, folding, packaging, and/or shipping. Typically, the compressed base region 183 opposite the adhesive hydrogel precursor structure 184 is free of hydrogel precursor. The adhesive hydrogel precursor structure 184 may be prepared by applying a blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor to a porous hydrophilic substrate, such as a crosslinked gelatin substrate, or applying the individual precursors as adjacent layers that may be blended to some extent during application, but still be adjacent along the patch area. In some embodiments, the porous hydrophilic substrate has a broken cell structure.

In some embodiments, the application of the precursor material is performed with the porous hydrophilic substrate under compression, such as using a printhead, to inject the hydrogel precursor into the substrate. In some embodiments, the adhesive hydrogel precursor structure 184 has a surface that conforms to one surface of the substrate 182. In other embodiments, the adhesive 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 an adhesive hydrogel precursor structure 184. In some embodiments, the porous substrate is prepared by calendaring prior to printing. In some embodiments, the cementitious hydrogel precursor structure 184 has cracks, such as microcracks and/or crazes. Compression substrate 172/182 may be a cross-linked gelatin substrate. In some embodiments, the compression substrate 172/182 is a porous sponge substrate. In some embodiments, compression substrate 172/182 is a compressed gelatin substrate, such as formed by compressing a rigid and/or cross-linked gelatin substrate. In additional or alternative embodiments, the compression substrate 172/182 is biodegradable. Typically, the hemostatic patch 170/180 is relatively thin, such as having an average thickness of no more than one centimeter, and is relatively flexible. The thickness, width and length of the patch may be appropriately selected according to the specific application. 1A, 1B, 1C, and 1D are presented as separate illustrations and do not imply that the features of the different illustrations are not properly combined or interchanged under the general discussion herein.

The size of the hydrogel precursor patch may be selected to suit the appropriate application. In addition, the total thickness is divided into a base thickness and a hydrogel precursor thickness. In this and the next paragraphs, the dimensions refer to the dimensions of the dry patch, and swelling from hydration is discussed further below. The area of the patch is generally not particularly limited, and may be selected according to a desired location of the patch. For commercial applications, different sizes may be allocated for user selection. Practical limitations will generally suggest patch areas for human patients of no more than 20 centimeters (cm) x 20cm, although larger patches may be used, and of these values any smaller range may be selected, such as 5cm x 5cm, 10cm x 5cm, 2cm x 4cm, etc. A convention may suggest a particular size for a particular application. Different sizes may be sold for a healthcare professional to select a desired size. In general, patches may also be cut to a size suitable for the particular situation encountered using instrumentation available in the operating room environment.

The thickness of the patch may depend on balancing the ability to bend the patch to conform to the application site and the ability to absorb the required amount of fluid and the absorption time. Thicker patches may be less flexible and may require longer time to hydrate and degrade, while thicker patches may absorb more blood and other fluids. Similarly, thinner patches generally absorb less, may be more flexible, and may degrade faster, thereby shortening the duration. The crosslinked hydrogel precursor layer typically provides all or most of the adhesiveness of the patch during its initial application. The substrate may be selected to provide a substantial amount of fluid absorption. In some embodiments, the patch may have a dry average thickness of about 0.25mm to about 10mm, in other embodiments about 0.3mm to about 9mm, in further embodiments about 0.35mm to about 8mm, and in other embodiments about 0.4mm to about 6 mm. The substrate 102/152/172/182 may have an average dry thickness of no more than about 10mm, in some embodiments may have an average dry thickness of about 0.2mm to about 8mm, in further embodiments may have an average dry thickness of about 0.25mm to about 7mm, and in still other embodiments may have an average dry thickness of about 0.3mm to about 5.5 mm. Precursor layers 104/154/174 can have an average thickness of about 25 microns to about 2mm, in further embodiments about 30 microns to about 1.75mm, and in other embodiments about 40 microns to about 1.5 mm. The precursor layer may partially penetrate into the substrate. In some embodiments, a significant portion of the precursor layer will remain on top of the substrate to present a dried precursor layer for patch applications. To evaluate the average precursor layer thickness, the average thickness can be calculated by dividing the precursor load per unit surface area (g/cm ²) by the precursor density (g/cm ³), or accurately estimated by applying the precursor layer on a non-porous substrate and measuring the dry average thickness (since the relatively dense character of the precursor layer should not be substantially altered by the substrate). While a patch may generally have these ratios of substrate and hydrogel precursor coating thicknesses, in some embodiments it is desirable that the dried substrate be at least as thick as the dried hydrogel precursor layer, in further embodiments at least about 60%, in some embodiments from 65% to 95%, and in other embodiments from about 70% to about 90% of the dried patch thickness is the substrate thickness. For ease of measurement, the substrate thickness includes any hydrogel precursor that penetrates into the substrate. Those of ordinary skill in the art will recognize that additional ranges of dimensions and thicknesses within the explicit ranges above are contemplated and are within the present disclosure. Typically, the hydrogel precursor layer may be added without significantly compromising the porous, absorbent properties of the substrate material.

More typically, in addition to gelatin-based substrates, in principle, suitable substrates for patches may be formed of natural materials, synthetic materials, or a combination thereof. Synthetic materials for the absorbent substrate include, for example, polyesters, polyurethanes, high molecular weight polyethylene oxide (PEO), or other reasonable synthetic polymers. Absorbable polyesters include, for example, polylactic acid, polyglycolic acid, or copolymers thereof. The high molecular weight PEO can slowly dissolve in water. Natural materials are often suitably processed for inclusion in medical products, and therefore they are often modified to varying degrees from their natural form. Nevertheless, natural materials can provide desirable properties suitable for substrates, including high absorption of aqueous solutions and degradation in vivo applications over a reasonable period of time. Suitable natural materials include, for example, polysaccharides and materials derived from extracellular matrix proteins. For example, polysaccharides that are derivatives of cellulose, pectin, hyaluronic acid, or chitosan may be used to make absorbent sheets. Commonly used materials are cellulose forms including, for example, ester and ether derivatives (such as cellulose acetate or ethylcellulose). Oxidized cellulose is a material that aids in hemostasis, but such materials are generally considered poorly absorbable and may cause postoperative complications, while hydroxycellulose, nitrocellulose or other forms may be appropriate.

Collagen is an extracellular matrix protein, which in its native form can be found in triple-chain fibrils. Purified collagen can take various forms, and gelatin is a partially hydrolyzed form of collagen. If desired, the collagen may be derivatized in other ways. Highly absorbable and absorbable collagen sponges have been developed, and these can be used alone as hemostatic elements. For example, commercial forms are sold by Becton, dickinson and Company under the trade names Avitene ^TM MCH and Avitene ^TM Ultrasponge. GELITA MEDICAL GMBH sells gelatin (collagen-based) hemostatic materials that can provide a basis for patch substrates. Custom substrates may be formed using commercially available medical grade collagen or gelatin (e.g., from GELITA MEDICAL or other suppliers) that is formed into a sheet, optionally with cross-linking (such as glutaraldehyde cross-linking), and dried (such as freeze-dried). Although crosslinking can stabilize collagen, strong chemical crosslinking can significantly increase duration.

Gelatin may be thermally and/or chemically crosslinked, such as with formaldehyde or glutaraldehyde, to mechanically stabilize materials suitable for use in substrates. Gelatin is a hydrolyzed form of collagen. The length of the thermal cross-linking again affects the duration. While not wanting to be limited by theory, it is believed that thermal crosslinking can affect crosslinking of adjacent suitable groups in the structure. In contrast, chemical crosslinking can form more complex crosslinked structures, which can provide significant entropy stability. Chemical crosslinking that is sufficiently prolonged can result in a substantially permanent/non-degradable material. Chemically cross-linked collagen has been used for several decades in prosthetic tissues, heart valves and other prostheses. Prior to thermal crosslinking, the gelatin is placed in the desired shape and then heated, for example in an oven or the like. Typically, thermal crosslinking may be performed at a temperature of about 100 ℃ to about 200 ℃ and in further embodiments at a temperature of about 120 ℃ to about 180 ℃ for a time of about 15 minutes to about 4 hours, and in further embodiments about 25 minutes to about 3 hours. One of ordinary skill in the art can adjust the time and temperature to achieve desired characteristics, such as porosity and mechanical stability, and duration after implantation in vivo, as discussed further below. With thermally crosslinked gelatin materials, the substrate may be foam, nonwoven tufted material, or nonwoven felted material. Those of ordinary skill in the art will recognize that additional ranges of temperatures and times within the explicit ranges above are contemplated and are within the present disclosure.

Commercial gelatin sponges are available in which the gelatin is foamed and may or may not be chemically crosslinked. The gelatin sponge illustrated in the examples is a foamed and uncrosslinked commercial material. The use of uncrosslinked gelatin avoids the concern for releasing potentially toxic chemicals for crosslinking. The resulting foamed gelatin material has a porous structure with a spongy cell structure. The density and pore size can be adjusted by processing parameters. Commercial materials may be designed to have suitable absorbency to absorb fluids at the wound site. While compression of the gelatin substrate was found to significantly improve flexibility, absorption was found not to change significantly. Absorbency can be assessed by placing the sponge into a volume of saline and evaluating the weight after the sponge is immersed and reaches a plateau of liquid absorption. For denser substrates, the plateau of swelling may take longer to reach, whereas for highly porous gelatin sponges, plateau may be reached faster, typically after about 10 minutes, most of the swelling is reached. While it is possible to wait longer for the measurement to take place after reaching the equilibrium state of swelling, it is possible to take the measurement after 24 hours to easily capture the swelling if desired, but the swelling measurement should be taken before the hydrogel breaks down significantly. For highly foamed gelatin sponges, a significant portion of the swelling can occur in less than one minute, while denser substrates may not reach plateau for significantly longer periods of time. The substrate typically absorbs at least about 100% of its dry weight of liquid, 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%, and typically the biocompatible substrate is capable of absorbing in the range of 100% to 2500% by weight of water relative to the weight of the dry patch. Typically, the initial uncompressed volume provides a rough upper limit on the solvent swelling weight and allows some swelling. In some embodiments, the compressed substrate (without the hydrogel precursor layer) may absorb at least about 80% of the liquid compared to the uncompressed substrate, in further embodiments may absorb at least about 90% of the liquid compared to the uncompressed initial substrate, and in some embodiments at least about 92.5% of the liquid, indicating that the compressed substrate may swell close to its uncompressed value. In an embodiment, the compressed substrate absorbs more than 98% of the liquid relative to the uncompressed substrate material. Those of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.

With regard to improved flexibility after compression, an evaluation can be made with respect to the respective base material which is not compressed. While thinner uncompressed materials may be more flexible than thicker versions, their absorbency is generally reduced by thickness variations and corresponding mass loss. Therefore, it is appropriate to compare versions having substantially the same absorbency. Since flexibility also depends on the initial thickness of the substrate and the materials used to form the substrate, there may be no particular significance in attempting to quantify improved flexibility. The flexibility of the substrate can be qualitatively compared by wrapping the substrate around a mandrel, in which case a more flexible substrate can typically be wrapped around a narrower mandrel without breaking. Thus, in some embodiments, the compression substrate may bend around a mandrel having parallel fold sides and a diameter of 5mm. However, the compressed substrate may lose mechanical strength. For a force to bend a material, the force (bending strength) is reduced, so the material can bend or fold more easily. Column strength (columnar strength) decreases, thus crushing the material with less force by squeezing the two opposite sides, which occurs reasonably because the cells have broken. The hydrogel precursor layer provides mechanical stability to the compressed substrate without significantly reducing flexibility along an axis parallel to the calender roll due to cracks in the hydrogel precursor layer.

The compression of the substrate may be performed in one or more compression stages. In particularly interesting embodiments, at least the last compression is performed after the precursor layer is added on top of the substrate and at least one compression step is performed before the precursor layer is deposited to provide a greater permeability of the precursor layer while leaving the top surface of the precursor layer. The subsequent compression step may be performed in such a way that the compressed thickness gradually decreases, although due to some responsiveness of the material, the subsequent compression may be performed at the same or possibly slightly wider compressed thickness. The initial gelatin sponge thickness provides the basic parameters for the final assembled structure, as modified by processing, which together determine the properties. The final compressed spacing is typically no more than about 85%, in some embodiments no more than about 65%, in some embodiments no more than about 55%, and in further embodiments from about 20% to about 50% of the initial average substrate thickness. In some embodiments, the lower limit of the compression range may be 5%, 10%, 15%, 20%, 25%, or 30% and the upper limit may be 85%, 75%, 65%, 60%, 55%, 50%, or 45%, and the range may include a combination of any of these lower limits with any of these upper limits. While the base material may have some rebound from compression, it may be desirable that at least about 40% of the compression step be maintained (rebound no more than about 60%), so compression from 2mm to 1.5mm will involve rebound to a final average thickness no more than about 1.8mm, making the gelatin less elastic, although in some embodiments the rebound may be 100% without net compression. In general, the rebound rate may be from about 0% to about 100%, in some embodiments from about 10% to about 90%, and in other embodiments from about 15% to about 80%, and in other embodiments from about 20% to about 70%. Those of ordinary skill in the art will recognize that additional ranges of relative compression and rebound ratios within the explicit ranges above are contemplated and are within the present disclosure.

Although in principle various methods are suitable for applying compression, the use of calender rolls or the like provides shear in addition to compression, as opposed to, for example, the use of flat plates. The shear across the roller along the edge applies additional force to break the cell structure of the sponge. In particular, when the hydrogel precursor layer is on a substrate, shear tends to fracture the hydrogel precursor layer, which further contributes to flexibility and faster hydration upon contact with body fluids. The nature of the crack typically depends on the amount of compression and the material properties, but the crack or fissure may or may not extend through the entire thickness of the hydrogel precursor layer. Although accurate characterization of the fracture is not particularly appropriate because the fracture location is random, in some embodiments there is typically a visible fracture per square centimeter of finished structure. Calender rolls are also particularly desirable for continuous production process flows.

Calender rolls and related conveying systems are well known in various industrial environments. Calender rolls have found wide application in polymer processing and food processing, and some equipment may be shared between different industries. For convenience, a pasta roller is used in the examples. Typically, commercial calender rolls have an adjustable thickness. Multiple calender rolls may be placed in series to perform sequential calendering steps, such as with reduced thickness, although other production configurations may use the same calender rolls sequentially, with appropriate adjustments between runs. As described above, the hydrogel precursor layer may be formed prior to a calendering step (such as the final calendering step). The formation of the hydrogel precursor layer is described in detail below. Although in principle a roll-to-roll process is possible, the foamed gelatin is typically formed into a block or other fixed shape that can be cut to the desired dimensions (including thickness). Thus, the process system can be designed to handle gelatin sponge sheets. In some embodiments, the sheet may be relatively large for subsequent cutting into individual patches for packaging. This allows the edge portions of the larger sheet to be discarded if the sheet is cut into individual sheets, which may have less uniformity depending on process considerations.

Because the components of the patch tend to be hydrophilic and/or hygroscopic, the components may be dried/dehydrated prior to processing to form the patch. Suitable drying techniques may include, for example, vacuum drying, thermal drying, desiccant drying, lyophilization, and the like, or combinations thereof. It may be desirable to have a hydration level of no more than 5% by weight water, in further embodiments no more than about 3% by weight water, in further embodiments no more than about 2% by weight water, or in some embodiments significantly lower. The water content may be determined by coulometric titration (KARL FISCHER) or loss on drying. Those of ordinary skill in the art will recognize that additional ranges within the explicit ranges of water content are contemplated and are within the present disclosure.

The hydrogel precursors may be selected to provide the desired absorption and crosslinking upon contact with physiological solutions while remaining stable as a coating during storage under dry (typically refrigerated) conditions to have a suitable shelf life, such as at least two months and in some embodiments at least about six months. The nucleophilic group may be a protonated amine, wherein the protonated form of the acidic amine is protected from the crosslinking reaction. Suitable electrophilic groups crosslink when the unprotonated amine is contacted in the same phase, whether in a mixture or dissolved in a solvent, which typically has a pH of at least about 7.1, which deprotonates the initially protonated amine.

With respect to buffering agents, no matter whether the hydrogel precursor changes pH and may in principle provide some buffering function, it is not considered a buffering agent. The amine precursor is provided in an acidified form, wherein the acidic protons act as protecting groups that block cross-linking. Upon contact with body fluids at physiological pH, the acidified amine may be deprotonated so that it can crosslink with the electrophilic precursor. The layer of uncrosslinked precursor may not include any significant added buffer and desirable patch performance was found without the addition of buffer. The buffer may be considered any bronsted base, which will generally be the anion (B ^-) corresponding to the weak acid (HB). Anions corresponding to strong acids (such as halide anions) do not act as aqueous buffers, and the amine precursor is typically provided as an HCl salt or similar strong acid analogue.

Typically, pH is used to control the crosslinking reaction, and the amine is provided in an acidified form, which inhibits crosslinking. Thus, avoiding a high pH buffer in the precursor layer avoids any premature crosslinking reaction by activation via the buffer. When the physiological fluid permeates into the patch at the time of use, the pH change caused by the physiological fluid rapidly deprotonates the amine and induces crosslinking. Because the precursors are mixed or in direct contact in the dry patch, the precursors can crosslink rapidly and have a relatively high initial crosslink density to provide good adhesion without waiting longer for more complete crosslinking to occur. The gel times are further described below.

In hydrogel systems, functional groups suitable for crosslinking monomers to form adhesive patches in situ may be advantageously used, including monomers, typically macromers as indicated below, containing electrophilic groups that are reactive with amine functional groups. Thus, the multicomponent hydrogel system may spontaneously crosslink upon activation of the components by contact with a physiological fluid, but two or more components are suitably stable for a reasonable process time before being activated by the physiological fluid. Such systems include, for example, difunctional or polyfunctional amine monomers (typically, but not necessarily, macromers) in one component, and difunctional or polyfunctional electrophilic group-containing macromers in another component, such as an N-hydroxysuccinimide ester-containing moiety. The N-hydroxysuccinimide ester functional group promotes amide bond formation in reaction with amines and has been used in other medical hydrogels, although other suitable electrophilic precursors are described below. N-hydroxysuccinimide ester is typically pendant from the hydrophilic core.

The hydrogel precursors may have cross-links that are activated by the physiological fluid with which the precursors are in contact after delivery. The hydrogel precursors described herein may be designed to hydrate relatively rapidly. Hydrogel and precursor solution characteristics are further described below. Parameters affecting the properties include functional group chemistry, crosslink density/molecular weight of the monomer, monomer composition, substrate composition, and patch structure.

The crosslink density of the resulting biocompatible crosslinked polymer is controlled by the total molecular weight of the macromer and the number of functional groups available per molecule. The lower molecular weight between crosslinks (such as 600 Da) gives a higher crosslink density than the higher molecular weight (such as 10,000 Da). Higher molecular weight macromers with significant branching provide desirable gelation times, and in some embodiments, in excess of 2500Da, to obtain an elastic gel. In certain embodiments, the molecular weight of the nucleophilic conjugate polymer (with the amine) is not significantly less than the electrophilic polymer. In some embodiments, they have the same dimensions (size) or larger.

The crosslink density may also be controlled by mixing the ratio of nucleophilic groups and electrophilic groups in the precursor material. For a dry solid precursor layer, the gel time is significantly dependent on the hydration time, since the crosslinking reaction can occur in water, and since the amine is deprotonated to be available for nucleophilic substitution. Rapidly hydrating the substrate can help hydrate the dried hydrogel precursor, and the size of the hydrophilic core in the precursor molecule can affect the hydration time. While not wanting to be limited by theory, it is believed that longer gel times may be associated with slower diffusion of physiological fluids into and/or slower diffusion of acid conjugate species out of the in situ placed patch. Another method of controlling the crosslink density is by adjusting the stoichiometry of the nucleophilic and electrophilic functional groups. The 1:1 ratio of electrophilic groups to amine groups should provide the highest crosslink density, although electrophilic groups in the precursor can in principle react with amines in physiological solutions as well as in proteins in tissues. In the examples, the desired properties were obtained using a functional group ratio of 1:1.

Monomer(s)

Monomers that can be crosslinked to form biocompatible structures (e.g., implants) can be used. As noted above, the monomer may be a macromer, which may or may not be a polymer. The term "polymer" as used herein means a molecule formed from at least three repeating groups, which may then have reactive functional groups pendant from the polymer. In general, the term "reactive precursor species" means polymers, functional polymers, macromolecules or small molecules that can participate in a reaction to form a network of crosslinked molecules (e.g., hydrogels). As noted above, for the formation of a rapidly crosslinked hydrogel precursor system, the monomer is typically (but not necessarily) a macromer, as indicated below, because the macromer typically allows for more rapid hydration and more rapid deprotonation of the amine.

The monomers may include, for example, biodegradable water-soluble macromers described in U.S. Pat. No. 7,332,566 (hereinafter the' 566 patent) entitled "biocompatible crosslinked Polymer with imaging agent (Biocompatible Crosslinked Polymers With Visualization Agents)", to Pathak et al, which is incorporated herein by reference. These monomers are characterized by having at least two polymerizable groups and may or may not be separated by at least one degradable region. After crosslinking, the product polymer forms a cohesive hydrogel which continues indefinitely or until eliminated by degradation, which may involve, for example, enzymatic reactions or hydrolysis. Typically, the macromer is formed with a core of a water-soluble and biocompatible polymer, such as a polyalkylene oxide, e.g., polyethylene glycol, which may be flanked by hydroxycarboxylic acids (such as lactic acid) to form a degradable ester or a non-degradable amide. In addition to being biocompatible and non-toxic, suitable monomers may also have at least some elasticity after crosslinking or curing. For electrophilic compounds or compounds having amine groups, the core of the compound may have multiple arms or branches, each arm or branch having a functional group suitable for crosslinking. PEG-based polymers having three or more arms are typically star polymers having a branched core and extended PEG polymer arms. As described above, polyethylene glycol (PEG) -based monomers are established medical hydrogel precursors, and precursor compounds having various arm numbers, molecular weights, and functional groups are commercially available.

The nucleophilic functional group is typically an amine group. Amine groups may be protonated in the form of protecting groups or gates (gates) to control crosslinking. The nucleophilic amine groups of the precursors can be designed to be significantly deprotonated at physiological pH values (such as about 7.1 to about 7.6pH units), although blood and tissue are typically in a narrower pH range in healthy individuals. While macromers are exemplary and provide the desired properties, trilysine has been used as a polyamine monomer in medical hydrogels, and similar compounds can be used. Electrophilic functional groups may be selected to undergo an addition reaction with amines to form crosslinks. N-hydroxysuccinimide ester is a desirable electrophilic group, although other suitable groups are described below. One or both of the functional groups may be pendant from the hydrophilic core, which may help provide the desired liquid swelling upon hydration. In some embodiments, the polymer may have moieties or linkages (linkages) that are biodegradable by hydrolysis, such as esters, carbonates, or other suitable linkages, although enzymatically degradable linkages may additionally or alternatively be present. Several such linkages are well known in the art and are derived from alpha-hydroxy acids, cyclic dimers (anhydrides) thereof or other chemicals 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 provide a degradable bond.

Typically, the monomers providing electrophilic functional groups and the monomers providing amine groups are macromers to provide more rapid hydration of the dried precursor layer. Macromers typically have a biologically inert and water soluble core with pendant reactive functional groups for crosslinking. When the core is a region of water-soluble polymer, the polymer that may be used may be a natural polymer or a synthetic polymer. Suitable polymers for the core may include polyethers, for example, polyalkylene oxides such as polyethylene glycol ("PEG"), polyethylene oxide ("PEO"), polyethylene oxide-co-polypropylene oxide ("PPO"), co-polyethylene oxide block or random copolymers, poloxamers such asF-127, and polyoxazoline, polyvinyl alcohol ("PVA")), poly (vinylpyrrolidone) ("PVP")), and polysaccharides such as hyaluronic acid, chitosan, dextran, or digestive cellulose, and derivatives thereof. Based on extensive experience with existing medical products, star branched polyethers and more particularly polyethylene glycols (also known as poly (alkylene oxides) or poly (ethylene oxides)) are particularly suitable. The acidifying amine or electrophilic group may be located at the end of the arm of each branch or a portion thereof. For PEG precursors, in the medical hydrogel field, one common notation involves the number and molecular weight of the arms and the functionality on the arms, such as 4a15k NH ₂ -HCl for 4-arm PEG with a molecular weight of 15,000 daltons and acidified amines with chloride ions, or 8a20k NHs ester for eight-arm PEG with a molecular weight of 20,000 daltons with N-hydroxysuccinimide ester functionality.

PEG-based hydrogels have been widely used in medical products. Therefore, they are widely accepted and PEG monomers with various functionalities are commercially available in medical grade form. Polyoxazolines are of interest as potential ideal alternatives to PEG-based products. Poly (2-oxazoline) has the structure- (CH ₂CH₂ N (COR)) -, wherein the R group may be H, an alkyl group, or other functional group. Amine-terminated poly (2-ethyl-2-oxazoline) is available from Sigma-Aldrich. The terminal functional monomer does not allow crosslinking, but a multifunctional electrophilic monomer having three or more functional groups can achieve crosslinking. Synthesis of poly (2-R-2-oxazoline) having N-hydroxysuccinimide (NHS) -ethyl group in 25% of the side chains is described in published U.S. patent application 2019/0125922 to Bender et al entitled "Tissue-adhesive porous hemostatic product (Tissue-Adhesive Porous Hemostatic Product)", which is incorporated herein by reference.

It has been determined that hydrogels formed from macromers with longer distances between crosslinking points are generally softer, more compliant, and more elastic. Thus, in the polymer of the' 566 patent, increasing the length of the water-soluble segment (such as polyethylene glycol) tends to increase the elasticity. As used herein, the molecular weight of a hydrophilic macromer (such as a macromer having a polyethylene glycol macromer core) is typically at least about 2,000Da, in some embodiments from about 2500Da to about 500,000Da, in other embodiments from about 5,000Da to about 250,000Da, in further embodiments from about 7500Da to about 100,000Da, in further embodiments from about 10,000Da to about 50,000Da, and in other embodiments in the range of from about 15,000Da to about 40,000 Da. The PEG precursors located in the lower part of these molecular weight ranges may be liquid. As used herein, molecular weight (mass) is in conventional units, which may equivalently be daltons or molar mass-grams/mole (assuming the presence of the natural isotope in either case), and for polymers, molecular weight is typically reported as an average if any molecular weight distribution is present. Those of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.

The hydrogel precursor in the hydrogel precursor solution has a certain ratio of electrophilic functional groups and amine functional groups. The ratio of functional groups can change the crosslink density and properties of the resulting hydrogels. In general, if the ratio of electrophilic functional groups to amine is one to one, the hydrogel can be fully crosslinked for a sufficient time and without limitation. In some embodiments, the ratio of nucleophilic functional groups to electrophilic functional groups is not less than 1. Generally, the ratio of electrophilic functional groups to nucleophilic functional groups may be from about 0.8 to 1.2, and in further embodiments from about 0.9 to about 1.1, and in further embodiments from about 0.95 to about 1.05, and in other embodiments from about 0.98 to about 1.02, and in further embodiments from about 0.99 to about 1.01, and in some embodiments, from about 0.995 to about 1.005, although the ratio may be about 1:1. Those of ordinary skill in the art will recognize that additional ranges of ratios within the explicit ranges above are contemplated and are within the present disclosure.

The functional groups may be distributed in various ways in order to achieve the desired ratio of functional groups. The pendant functional groups extending from the core may be referred to as being associated with the arms of the precursor. The precursor typically has 2, 3,4, 5, 6, 7, 8, 9, 10 or more arms. At least one precursor typically has at least 3 arms to achieve crosslinking, and 4-arm, 6-arm or 8-arm precursors may be conveniently used to achieve the desired hydrogel properties. To obtain a one-to-one ratio of functional groups, equimolar amounts of precursors may be used if they have the same number of arms, or the molar ratio may be adjusted accordingly if different numbers of arms are present on each precursor. Thus, a double molar amount of 4-arm precursor can be combined with an 8-arm precursor to obtain a 1:1 ratio of functional groups. For the weight ratio, the molar ratio can be adjusted accordingly based on the relative weight, which for the 8 arm 10K MW (10,000 molecular weight) precursor will be combined with twice the mass of the 8 arm 20K MW precursor to obtain a 1:1 functional group ratio. Those of ordinary skill in the art can adjust these calculations to achieve different quantitative ratios of functional groups.

Functional groups and crosslinking reactions

The crosslinking reaction is typically designed to occur upon hydration with an aqueous fluid, which is essentially an in vivo physiological fluid surrounded by physiological conditions, although medical procedures may involve some local dilution or modification of the physiological fluid, such as the use of disinfectants or other procedure emergency means, which begin in its purely natural state without altering the basic processing of the hydrogel precursor. To aid in hydration, the substrate may be wetted prior to application of the patch to tissue, as further explained below. Unless explicitly stated otherwise, references herein to physiological fluids may refer to minor changes to natural fluids due to medical procedures. Thus, the crosslinking reactions occur "in situ", meaning that they occur at a localized location, such as an organ or tissue in a living animal or human. Due to the in situ nature of the reaction, the crosslinking reaction can be designed not to release an undesirable amount of heat of polymerization. The gelation time of the desired procedure is described above, and complete communication is typically accomplished after 2 minutes to 10 hours, although other times outside of this range may be acceptable. Longer complete crosslinking times may begin to compete with degradation times.

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, by using activating groups such as N-hydroxysuccinimide or derivatives thereof, these functional groups can be made more reactive. In general, several methods for activating these functional groups are known in the art. Suitable activating groups include, for example, carbonyl diimidazole, sulfonyl chloride, chlorocarbonate, aryl halides, sulfosuccinimidyl esters, N-hydroxysuccinimidyl esters (NHS), succinimidyl esters, succinimidyl amides, epoxides, aldehydes, maleimides, imidyl esters, and the like. N-hydroxysuccinimide ester or N-hydroxysulfosuccinimide groups are ideal groups for cross-linked amine-functionalized polymers such as amino-terminated polyethylene glycols ("APEG") because they have been approved in medical implants for long term use in the approved product. Further broad discussion of general medical hydrogels is disclosed in U.S. patent 7,332,566 to Pathak et al entitled "biocompatible crosslinked Polymer with imaging agent (Biocompatible Crosslinked Polymer With Visualization Agents)", which is incorporated herein by reference.

Suitable nucleophilic functional groups are polymers having primary amines conjugated to acids. Thus, another functional group for crosslinking is typically an amine. The amine is a weak base. In some embodiments, the acid conjugate is HCl and an amine (such as PEG amine) HCl salt is formed. The acid conjugate may be selected to match the approximate molar concentration of the amine. The advantage of the NHS-amine reaction is that the reaction kinetics result in rapid gelation, typically within about 10 minutes, more typically within about 1 minute, and most typically less than 30 seconds. The gelation time may be limited by the hydration time of the dried hydrogel precursor. Protonated amines are generally unsuitable for nucleophilic substitution. Thus, the precursor blend may be prepared at a suitable pH to maintain the substantially protonated amine prior to delivery for contact with the physiological solution.

The crosslink density of the resulting biocompatible crosslinked hydrogel is controlled by the total molecular weight of the monomers and the number of functional groups available per molecule. A lower molecular weight between crosslinks (such as 2000 Da) will give a higher crosslink density than a higher molecular weight (such as 100,000 Da). Higher molecular weight monomers may be used to obtain hydrogels that are more elastic, while correspondingly lower molecular weight monomers may be used to obtain hydrogels that are less elastic. Different applications may mean that the hydrogel has different properties.

Another method of controlling the crosslink density is by adjusting the stoichiometry of the nucleophilic and electrophilic functional groups. The one-to-one ratio may result in the highest crosslink density. Typically, over time, the hydrogel completes curing, allowing the available crosslinking sites to form crosslinks. If the electrophilic and nucleophilic groups are provided in equivalent amounts, it is expected that almost all functional groups will form crosslinks after complete curing. Equal amounts (or reaction equivalents) of both types of reagents generally provide the highest crosslink density. If different ratios of functional groups are used, the properties of the cured hydrogels may correspondingly vary. The crosslink density may depend on the number of functional groups on the precursor molecule and the ratio of precursor molecules. If desired, the cross-linking density can be varied using a non-stoichiometric ratio of electrophilic and nucleophilic groups. The ratio of functional groups is further described above.

Degradable or non-degradable bonds

In general, it is desirable that the patch be degradable, and in some embodiments relatively rapidly degradable. Thus, if patches are implanted, they do not last indefinitely. To degrade the patch, both the substrate and the in situ formed hydrogel degrade. Depending on the application, it may or may not be desirable for the hydrogels to be degradable, such as by hydrolysis or biodegradation due to enzymatic activity, although for hemostatic patches, patches are typically designed to degrade rapidly so they do not last long after stable clotting. If it is desired that the biocompatible crosslinked hydrogel polymer be degradable or absorbable, one or more precursors having degradable linkages between functional groups may be used. As used in the art, absorbable polymers may be referred to as biodegradable if they are absorbed under physiological conditions, whether or not they degrade by biological action (such as enzymatic cleavage). The degradable linkages may also optionally be used as part of the water-soluble core of one or more precursors. Alternatively or additionally, the functional groups of the precursors may be selected such that the reaction product between them produces a degradable bond. For each method, the degradable linkages may be selected such that the resulting degradable biocompatible crosslinked hydrogel polymer degrades or is absorbed over a desired period of time. In other embodiments, the functional groups and bonds (linkages) with functional groups may be selected to resist degradation under physiological conditions, thereby significantly reducing or eliminating absorption of the patch.

Typically, the degradable linkage is selected so as to degrade the hydrogel under physiological conditions into non-toxic products for removal from the patient by a natural route. Exemplary enzymatically hydrolyzable biodegradable bonds include peptide bonds cleavable by metalloproteinases or collagenases. Further exemplary biodegradable linkages may be functional groups on the core polymer and copolymer such as hydroxycarboxylic acids, orthocarbonates, anhydrides, lactones, amino acids, carbonates, phosphonates, or combinations thereof. In an exemplary embodiment, the degradable linkage is an ester formed from a hydroxycarboxylic acid moiety adjacent to the electrophilic group for crosslinking. Esters can be gradually degraded by hydrolysis under physiological conditions, with the duration depending on the specific structure. To obtain a non-degradable hydrogel, the ester formed of the hydroxycarboxylic acid moiety may be substituted with an amide group that is generally not hydrolyzed under physiological conditions. Monomers with PEG cores are commercially available with N-hydroxysuccinimide electrophilic groups attached with amide or alternatively ester linkages, e.g. from Jenkem Technology, TX, u.s.a. PEG-amines are also available from Jenkem, which have various arm numbers and molecular weights. Desirable degradable electrophilic groups include, for example, N-hydroxysuccinimidyl succinate (SS), N-hydroxysuccinimidyl succinate, N-hydroxysuccinimidyl glutarate, succinimidyl Glutarate (SG), succinimidyl Adipate (SAP), succinimidyl Azelate (SAZ), or mixtures thereof. Examples of rapidly degrading patches with SS linking groups are described below. Mixtures of degradable and non-degradable linkages (such as the amides described above) can be used to adjust the duration, for example, to form oligomeric species for clearance by the body.

Hydrogel and patch properties

The evaluation of patch properties can be performed in vitro under specific conditions such that the properties are independent of biological conditions. Such evaluation helps to characterize the patch, which is very important for practical in vivo use. Herein we describe measurements of gel time, swelling, substrate porosity, burst strength and duration, and in the examples the corresponding measurements were made. However, for patch performance evaluation in actual procedures, a regimen may be used to provide appropriate limitations of patch behavior under test conditions that simulate bleeding tissue, thereby providing a repeatable background for patch evaluation. The following examples demonstrate the results of in vitro tests, in which a comparison was made with the actual use of animal models. For dry patches, the density of the patches (substrate and precursor layers) may be from about 0.075g/cm ³ to about 0.5g/cm ³. For the individual precursor layers, the density may be from about 0.050g/cm ³ to about 0.450g/cm ³. Those of ordinary skill in the art will recognize that additional ranges of densities within the explicit ranges above are contemplated and are within the present disclosure.

The gel time of the sample patch can be evaluated in a laboratory setting, which provides a suitable estimate of in vivo performance. Examples measurements were made on specific samples. Gel time was evaluated using a commercial texture analyzer. Texture gauges are available from Texture Technologies corp./Stable Microsystems, ltd. (such as model TA-XT Plus) and Brookfield Technologies (such as model CTX texture gauges). These systems are designed to analyze food and soft medical materials. The instrument is first calibrated using a standard test block following the standard procedure of the instrument. A TA-005 probe (Texture Technologies) having a 1/4 inch diameter and a flat surface (alternatively hemispherical) can be used with a 5kg load cell. The sample holder was heated to 37 ℃ to track standard body temperature. The sample holder was a non-porous polymer foam block with a 1.5mm hole cut in the middle. An 8mm diameter punched sample from the patch was placed on top with the sample holder well as a center, with the precursor layer facing down. To begin the test run, the tester was started and 67 microliters (μl) of 37 ℃ buffer solution (pH 8.0) was added to the 8mm stamped sample to the center of the test sample. The texture analyzer may be programmed accordingly to meet these parameters. The force required to deform the patch by 0.4mm was determined as a function of time.

The graph as a function of time yields a characteristic curve. The patch is initially in a dehydrated state and is stiff, so the initial force is relatively high. In the course of a few seconds, the patch will hydrate and the force is minimized. It is expected that crosslinking starts during hydration and proceeds to early treatments. As the crosslinking continues, the force begins to increase, indicating that the crosslinking has reached a point where the material is solid. The time at which the force starts to increase is considered as the gel time, which marks the point of gelation at which the gel starts to become firm. In these systems, the use of patches involves hydration during which the solid precursor hydrates and begins to crosslink. Thus, dissolution of the precursor is counteracted by crosslinking. As hydration begins, the solids soften until crosslinking proceeds sufficiently to begin to make the hydrogel firm. The gelation process has different characteristics from a solution-based hydrogel system starting from a dissolved precursor. After gelation begins, the force continues to increase as crosslinking continues. Three equivalent punches from the same patch were measured three times and the results averaged. For the patches described herein, the gel time is typically no more 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. Those of ordinary skill in the art will recognize that additional ranges of gel times within the explicit ranges above are contemplated and are within the present disclosure.

The burst pressure of the patch samples can also be tested and these values are ideal to ensure that the samples have the desired properties in actual use. Burst pressure measurements are intended to provide standard test conditions related to the adhesion of the patch to bleeding tissue. As described above, some patches may be formed with a compressed gelatin substrate that desirably provides a more flexible structure and/or a more uniform substrate surface while maintaining sufficient rigidity to resist warping/deformation of the substrate during coating. The results presented in the examples below demonstrate that patches with compressed gelatin substrates exhibit approximately the same burst pressure. Experience to date has shown that patches with compressed gelatin substrates exhibit more uniform performance. The same samples can then be used to evaluate swelling as described later in the burst test description. Burst tests can be evaluated on equipment designed to simulate bleeding tissue, which is suitable for measurement according to ASTM F2392-04 (2015). The ASTM protocol provides information related to the surface of the test fixture, which is then adapted for use with the multiwell plate of the test fixture. It is believed that there is no commercial version of such a test instrument, but for a patch test to be used clinically, the corresponding test would be highly desirable. Thus, in view of and in compliance with the ASTM protocols described above, similar test apparatus with regulatory effects are constructed in the design, as further described in the examples below.

For testing, a calibrated syringe pump was used, with a 60ml syringe tube filled with saline and the pump set at 2ml/min. A burst fixture is used with a cavity connected to the syringe pump, wherein the cavity top has a circular opening. A pressure sensor (such as a digital manometer) is also connected to the cavity to measure the pressure in the cavity. To begin the test, the cavity was filled using a syringe pump until the cavity was nearly full. The test block with the patch sample in the gelation test was placed on the well on top of the fixture with the patch punch sample facing upwards. Similarly, hydrated patches pressed against the test block may be similarly used, but using a patch after the gelation test provides a uniformly prepared patch for burst testing. In this configuration, the hole in the sample holder is located in the center of the burst fixture cavity. The upper half of the fixture is then secured to the test block to secure the sample holder with the aperture connected to the cavity extending through the upper half of the fixture exposing the sample from the top. Once the top fixture secures the test block, an increase in pressure measured on the manometer is expected.

After the securing device is secured in place with the top, the pump is activated to pump water into the cavity to continuously increase the pressure in the cavity. The pump was run until 1) the surface of the patch sample had developed a liquid, 2) a pop sound was heard, or 3) the maximum pressure recorded on the manometer had not changed within 30 seconds. Once the conditions have been reached, the pump is stopped and the maximum pressure value obtained is recorded as burst pressure, in millimeters of mercury (mmHg). For the patch samples described herein, the burst pressure may be at least about 10mmHg, in further embodiments at least about 15mmHg, in further embodiments at least about 50 mmHg, and in other embodiments from about 20mmHg to about 1500mmHg. Those of ordinary skill in the art will recognize that additional ranges of burst pressures within the explicit ranges above are contemplated and are within the present disclosure.

After hydration, both the substrate and the precursor layer swell. Although swelling can in principle be assessed in several reasonable ways, swelling is assessed herein by the weight due to water retention. For embodiments based on compressed substrates, the weight-based swelling may not change significantly, and thus the overall swelling evaluation may be substantially unchanged relative to a similar patch assembled on an uncompressed substrate. The dry weight of the patch before testing can be used as an initial reference point. Finally, swelling can be assessed based on incubation with aqueous fluids, but over a longer period of time, the patch material may degrade. Essentially, the swelling described herein is evaluated over a period of time long enough to allow the swelling to reach a steady state after incubation in 37 ℃ phosphate buffered saline, which may be after about 24 hours for a denser substrate, or about ten minutes for a highly foamed gelatin sponge. The sample used for evaluation may be the same sample used for other property measurements, and this uses the hydrated, non-submerged weight as a reference point to provide a consistent swelling estimate. If swelling is assessed directly from a dry sample, air can be forced out of the sample at an early stage of swelling to achieve proper measurement without significant delay. In some embodiments, the sample at the end of the burst test may be used to further evaluate swelling. After the burst test is completed, the sample may be carefully removed from the sample holder. The sample is then weighed to obtain an initial weight. The weighed sample was then placed into a 50ml tube containing approximately 45ml Phosphate Buffered Saline (PBS) and sealed. PBS is a standard buffer for medical and other biological applications and typically contains sodium chloride, some potassium chloride, and phosphate. PBS is available from standard suppliers (FISHER SCIENTIFIC, sigma-Aldrich, etc.) and is classified in PubChem (https:// pubchem. Ncbi. Nlm. Nih. Gov/compound/Phosphate-Buffered-Saline). The sealed tube was placed in a 37 ℃ water bath. After 24.+ -. 2 hours, the tube was removed from the water bath. Then, the incubated sample was removed, patted dry and weighed. The value of the percent swelling is determined by the following formula:

% swelling = 100× (output weight-input weight)/input weight.

The value of the "input weight" may be the dry weight or a weight corresponding to an alternative reference point, such as the weight after a burst test. For the patches described herein, swelling (from post burst test to incubation in PBS for 22-26 hours) may be at least about 100%, in further embodiments from about 135% to about 350%, and in other embodiments from about 150% to about 300%. Those of ordinary skill in the art will recognize that additional ranges of swelling within the specific ranges described above are also contemplated and are within the scope of the present disclosure.

Although the substrate has a high swelling weight, it is initially porous and thus the volume swelling may be weak. If the substrate is initially compressed relative to its original formed size due to cell breakage, swelling may restore some or most of the original size of the structure. The hydrogel precursors are initially dense, so that upon crosslinking and swelling, the volume change of the crosslinked hydrogel is generally more pronounced. Thus, after hydration and swelling, the volume increase of the hydrogel layer may be more pronounced than the substrate volume change.

Another important characterization is the persistence (persistence) of the patch. In vitro measurements may be made to obtain consistent measurements to simulate in vivo behavior. The substrate and associated crosslinked hydrogel layer may vary in duration from one another. The sustainability behavior of the substrate can be evaluated by continuing the swelling test. In particular, the sample loaded into the tube containing PBS may be kept in a 37 ℃ hot bath until the substrate of the patch sample is no longer visible. The time at which the sample substrate disappeared is considered to be the end of the substrate duration. Typically, the substrate disappears in no more than 96 hours, in further embodiments in no more than about 84 hours, and in further embodiments in about 15 minutes to about 72 hours. In some embodiments, it is desirable that the substrate disappear in no more than about 48 hours. Those of ordinary skill in the art will recognize that additional ranges of degradation times within the explicit ranges are contemplated and are within the present disclosure. Typically, hydrogels formed in situ last longer than the substrate.

Imaging agent

In a convenient case, the biocompatible crosslinked hydrogel polymer may contain an imaging agent to improve its visibility during a medical procedure and provide rapid confirmation of the patch orientation relative to the surface for placement against a wound. In principle, the substrate may have an imaging agent in addition to (the same or different from) the hydrogel precursor layer, or as an alternative to the hydrogel precursor layer. The patch in the example has a blue developer only in the hydrogel precursor layer. As used herein, imaging agent may refer to optical visualization (colored), or visualization using imaging means (such as x-ray or ultrasound). Imaging agents are particularly useful when used in Minimally Invasive Surgical (MIS) procedures, such as laparoscopy, one of which is their improved visibility on color monitors. It is sometimes useful to provide color by adding a colored imaging agent to the precursor melt prior to casting the hydrogel layer onto the substrate.

The imaging agent (optical) may be selected from any of a variety of non-toxic colored substances suitable for use in medical implantable medical devices, such as FD & C blue dyes 1,2, 3 and 6, indocyanine green, or colored dyes commonly found in synthetic surgical sutures. In some embodiments, green or blue colors are desirable because they have better visibility in the presence of blood or on pink or white tissue backgrounds. The dye may be added in trace amounts to the melt blend as a dewatering compound to form a dry hydrogel layer.

The selected colored substance may or may not be chemically bound to the hydrogel. Other imaging agents may be used, such as fluorescent (e.g., green or yellow fluorescent under visible light) compounds (e.g., fluorescein or eosin), X-ray contrast agents for visualization under an X-ray imaging device (e.g., iodinated compounds), ultrasound contrast agents (e.g., microbubbles), or MRI contrast agents (e.g., gadolinium-containing compounds). The biocompatible imaging agents FD & C BLUE #1 and fluorescein-NHS may be particularly desirable in some applications. The imaging agent may also be a bioactive agent suspended or dissolved in the hydrogel matrix, or a material for encapsulating the bioactive agent, if present.

As noted above, visually observable imaging agents may be advantageously used in some embodiments. Light having a wavelength of about 400 to 750nm can be observed by humans as a color (R.K.Hobbie, intermediate Physics for MEDICINE AND Biology, 2 nd edition, pages 371-373). Blue is perceived when the eye receives light having a dominant wavelength of about 450 to 500nm, and green is perceived when the eye receives light having a dominant wavelength of about 500 to 570 nm. Further, since the eye detects red or green or blue, a combination of these colors can be used to simulate any other color by simply having the eye receive the ratio of red, green, and blue that the human eye perceives as the desired color. Blue as used herein means a color perceived by a normal human eye at a wavelength stimulus of about 450 to 500nm, while green as used herein means a color perceived by a normal human eye at a wavelength stimulus of about 500 to 570 nm.

One or more imaging agents may be present in the final electrophilic-nucleophilic precursor layer at a concentration suitable for visualization, such as from about 0.0001 mg/square centimeter (g/cm ²) to about 0.5g/cm ², although higher concentrations up to the solubility limit of the imaging agent may be used. In some applications, these concentration ranges were 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 imaging agent is generally not covalently linked to the hydrogel. Those of ordinary skill in the art will recognize that additional ranges of imaging agent concentrations within the explicit ranges above are contemplated and are within the present disclosure.

The imaging agent may be used to help visualize the interface of the patch with the underlying tissue. In some embodiments, the dye is conjugated to electrophilic or nucleophilic end groups for incorporation into a patch for visualization as well as direct correlation to persistence. In some cases, the dye is fluorescent such that visualization is achieved only under special light conditions and the monomer-based gel is rendered invisible under normal visual conditions.

The user may use the imaging agent to view the hydrogel with the human eye or by means of an imaging device (e.g., a camera) that detects the visually observable imaging agent. A visually observable imaging agent is an agent having a color that is detectable by the human eye. The characteristics that provide imaging for an X-ray or MRI machine are not sufficient to establish the function of a visually observable imaging agent. An alternative embodiment is an imaging agent that is not normally visible to the human eye, but is detectable at a different wavelength (e.g., infrared or ultraviolet) when used in combination with a suitable imaging device (e.g., a camera). Similarly, an acoustically transparent agent (such as a bubble) can provide improved imaging by ultrasound. Hydrogels with imaging agents for X-ray and/or ultrasound visualization are further described in U.S. patent 8,383,161 to Campbell et al entitled "radiopaque covalently crosslinked hydrogel particle implants (Radiopaque Covalently Crosslinked Hydrogel PARTICLE IMPLANTS)", which is incorporated herein by reference.

The radiopaque moiety may be introduced through a radiopaque precursor molecule or covalently attached to a hydrogel functional group. For example, the triiodobenzoate may be bound to one arm of the precursor at the ester group. The total number of arms may be selected to achieve the desired cross-linking and radiopacity. CT numbers (also known as Hounsfield units or Hounsfield numbers) are a measure of visibility under indirect imaging techniques. A CT number of at least about 50 may be used, and in some embodiments, the CT number may be about 70 to about 2000.

Method for forming patches and storage

The method for preparing the patch includes the steps of taking the substrate, applying the precursor layer and packaging in a water-resistant package, and optionally drying one or more times throughout the process. The method may further comprise preparing the substrate if the substrate is not a commercial product. If the substrate is of commercial origin, processing may include cutting a substrate of the appropriate size from a larger piece or pieces of material. Some suppliers may offer gelatin substrate sheets having the desired initial thickness. For commercial production, the process may produce a patch of patch material with a hydrogel precursor layer, which may then be cut to size. The dimensions may generally comprise a set of commercial dimensions for selection by a healthcare professional as appropriate, and it should be noted that the patch may be cut to size as desired at the time of use, as described above. Application of the precursor layer may include delivering a melt blend or solution coating with a non-aqueous precursor solution, and layer deposition may optionally include forming a sub-layer. The water content can be reduced below the target amount of packaging and, because materials are generally hygroscopic, processing is typically performed in an enclosed environment with low levels of water vapor. The packaged patch is labeled with a use label and date to reflect proper shelf life and proper dispensing.

The substrate may be purchased in a form to be used or may be processed from a suitable starting material. For gelatin substrates, these may be obtained as foamed sheets, which are subsequently calendered, coated and otherwise further processed. The purchased materials may be purchased according to product specifications and the desired patch characteristics as described above, the substrate is selected accordingly to meet these characteristics. Whether purchased or further processed to prepare the material for patch formation, the substrate may be further dried prior to the addition of the precursor layer. Drying may be performed by various methods, such as placing in a drying oven, contacting with a drying gas, isolating with a desiccant, combinations thereof, and the like. A suitable drying oven may be selected based on the size of the base material, and heating may be continued until the relative humidity falls below a target value. The heat treatment can be carried out under suitably mild conditions so that the properties of the material do not change in an undesired manner. Suitable desiccants are commercially available, such as zeolites, calcium chloride, calcium sulfate, and the like.

In some embodiments based on gelatin sponge material as a substrate, the starting material may be purchased or produced. In either case, the material may be cut to a specified thickness for further processing, if appropriate. Typically, a particular patch size may not be cut to size prior to application of the hydrogel precursor layer and compression, although some final processing may be performed after cutting to size. Commercial suppliers of gelatin sponge materials include, for example, ethicon (USA), gelita (Germany), pfizer

In some embodiments, the precursor layer may be formed using a solvent coating process. The solution of the precursor should be non-aqueous to avoid introducing water that would need to be removed and to avoid deprotonation of the amine. However, the precursor should be soluble in the solvent. Suitable solvents may include, for example, aromatic liquids such as toluene, xylene, chlorobenzene, ethylbenzene, and the like, alkanes such as hexane, or aprotic solvents such as tetrahydrofuran, ethyl acetate, acetone, acetonitrile, dimethylsulfoxide, blends of any two or more of these liquids, and the like. In general, the concentration should be selected to be as high as possible compatible with the process conditions (such as viscosity) so that a uniform coating can be applied with a smaller amount of solvent. One of ordinary skill in the art can select the concentration based on the coating technique selected and the solvent selected. The solution may contain imaging agents and possibly other additives such as biological/therapeutic agents. Suitable coating techniques include, for example, spray coating, jet printing, slot coating, screen printing, extrusion, and the like. Extrusion, as is well known in the art, typically means a different range of viscosities and solids concentrations than spraying.

The advantage of using a solvent-free process is that the use of solvents and associated waste disposal is avoided. The flow temperature of polyethylene glycol (PEG) based precursors is quite low, typically below 100 ℃, and relatively weakly dependent on molecular size. Some low molecular weight PEG-based precursors may be liquid at room temperature, which may be blended with precursors that are solid at room temperature to form a solid blend. Polyoxazolines generally have moderately high flow temperatures, which may be from about 150 ℃ to 250 ℃ depending on the side chain and molecular weight. Thus, a blend of PEG-based precursors can be formed at relatively low temperatures and suitably coated onto a substrate using any reasonable technique. The precursor layer may contain imaging agents and possibly other additives such as biological/therapeutic agents. While other coating techniques may be used for melt deposition, slot die coating may be a convenient technique because suitable commercial equipment can maintain the material at the proper temperature while setting an adjustable coating thickness. The apparatus may be selected to match the desired substrate size and the substrate may be conveniently supplied in sheet or web 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).

Fig. 2-4 illustrate various means for forming a patch 100 of a closure that can be used as a hemostatic patch. Referring to fig. 2, a spray coating device 200 has a precursor blend 202, which may be a melt blend or an organic solvent blend, in a vessel 204. The precursor blend 202 can be a net mixture of molten precursors. Alternatively, the precursor blend 202 may be a melt blend with one or more additional components to reduce viscosity. Additional components may include, for example, solvents such as anhydrous organic solvents. The container 204 can mix and/or heat the precursor blend 202 prior to delivery through the nozzle 205. The precursor blend spray 206 is deposited onto a substrate 208 to form a sealant patch composition having a coating of mixed unreacted precursors on the substrate 208. In some embodiments, the formed closure patch composition is dried to remove solvent and/or residual water. In some embodiments, the formed closure patch composition is cut into individual patches and stored in a humidity controlled package or container.

Referring to fig. 3A, a slot-die coating apparatus 300 has a melt blend 302 in a vessel 304. Melt blend 302 may be a neat mixture of precursors. Alternatively, melt blend 302 may have one or more additional components to change viscosity, such as an organic solvent. The container 304 can mix and/or heat the melt blend 302 prior to delivering the melt blend 302 through the slot die 306 to form a film 308 on the substrate 310. Apparatus 300 may use additional equipment such as filters, pumps, pulsation dampers, degassing units, and/or flow regulators between vessel 304 and slot die 306. Typically, the film 308 is a continuous liquid film. Suitable slot coaters are commercially available and in the examples the use of a commercial slot coater is described. Slot die 306 may have various head sizes, viscosity grades, and fringe pattern options. The width of the film 308 may be selected according to the selection of the slot die 306. The width of the film and slot die may be selected to match the width of the desired product, or it may be wider than the width and cut to size after coating, such as a number of times the width of the product and cut to form multiple products of coated substrates per length. Slot die 306 may be used to control the deposition rate of melt blend 302 on substrate 310, which is related to the precursor thickness on the substrate. For coating deposition using a slot die, the die and substrate are moved relative to each other, which may include substrate movement, slot coater and die movement, or both. The apparatus 300 may be similarly used to apply a solvent blend.

As described above, it may be desirable to deposit a liquid hydrogel precursor material (melt or non-aqueous solution) on and/or within a porous substrate under compression. As shown in fig. 3B with respect to slot-die coating apparatus 350, slot-die 356 may be used to control the deposition rate of melt blend 302 and to inject melt blend 302 into substrate 310. To perform injection of melt blend 302, slot die 356 and substrate 310 are moved relative to each other, wherein slot die 356 compresses substrate 310 at the injection location. The force applied to the substrate 310 by the slot die 356, the depth to which the slot die 356 compresses into the substrate 310, and/or the deposition rate may be adjusted to tailor the adhesive hydrogel precursor structure formed. In some embodiments, the depth of compression is from about 0.02mm to 2mm, in further embodiments from about 0.05mm to about 1mm, and in further embodiments from about 0.2mm to about 0.8mm. In other embodiments, the depth of compression is from about 5% to about 30% or from about 5% to about 15% of the thickness of the substrate prior to coating. Those of ordinary skill in the art will recognize that additional ranges of compression for coating within the explicit ranges above are contemplated and are within the present disclosure. The porous substrate 310 may have a certain elasticity. Thus, under relatively gentle compression during coating, the substrate may rebound to approximately the original substrate thickness, as shown in fig. 3B. While properly modified slot die printheads can effectively apply moderate compression, secondary structures can be used to effect moderate compression near the printhead, and calender rolls or the like can be used to achieve such an objective.

In some embodiments, referring to fig. 3A, during deposition of melt blend 302, substrate 310 is moved as indicated by directional arrow 312 and slot die 306 may remain in place. The rate at which the substrate translates along directional arrow 312 and the parameters of slot die 306 may be adjusted to vary the thickness of film 308. If multiple layers are desired, the substrate may be translated back in the opposite direction to form a second layer, or translated back without coating and translated forward along directional arrow 312 to further apply a subsequent coating. Similar multiple coating can be performed based on the embodiment in fig. 3B. The substrate may be supplied as a separate unit which is coated and subsequently cooled and/or dried for packaging. In other embodiments, the substrate may be provided as a larger sheet that is cut to size after coating, and the larger sheet may or may not be provided in roll form. The dry gelatin substrate is typically provided as a relatively rigid sheet.

In other embodiments, substrate 310 does not move during deposition of melt blend 302, but rather slot die 306 (fig. 3A) or slot die 356 (fig. 3B) moves along directional arrow 314. In further embodiments, the substrate 310 is not moved and the slot die 306 or 356 is moved in the direction indicated by directional arrow 314 for a period of time or until a selected travel distance is reached, and then moved in the opposite direction indicated by directional arrow 316 for a period of time or until a selected travel distance is reached. Film 308 may be formed from a single deposited layer of melt blend 302 or from multiple deposited layers of melt blend 302. In some embodiments, film 308 is formed by alternately depositing melt blend 302 while moving slot die 306 or 356 along directional arrow 314 to form a first deposited layer, and then depositing melt blend 302 while moving slot die 306 or 356 along directional arrow 316 to form an additional deposited layer on the first deposited layer. Alternate depositions may be repeated a selected number of times to achieve a desired thickness of film 308.

In some embodiments, the film 308 cools to form a coating 309 as a solid on the substrate. For many applications, the coating 309 may be a continuous solid phase hydrogel precursor network that is bonded to the substrate 310 and at least partially integrated into the substrate 310. In some embodiments, the film 308 and/or coating 309 is dried to remove solvent and/or residual water. The apparatus 300 may be used to form a hydrogel precursor patch composition comprising a coating 309 on a substrate 310. In some embodiments, the formed structure having the hydrogel precursor patch composition on a substrate is cut into individual patches and stored in a humidity-controlling package.

Fig. 4A is an embodiment of a roll slot die coating apparatus 400 having a substrate roll 402 with a substrate 404 moving from the substrate roll 402 to below a slot die 405 by a belt 401 moving at a selected rate. The belt 401 may be any convenient conveyor system and may be replaced by a series of rollers or the like. The vessel 406 contains a precursor blend 408, which may be a melt blend or an inert organic solvent solution. Precursor blend 408 can be a net mixture of precursors. Alternatively, the precursor blend 408 may have one or more additional components to alter the viscosity, such as a solvent. The container 406 can mix and/or heat the precursor blend 408 prior to delivering the precursor blend 408 through the slot die 405 to form a film 410 on the substrate 404. The coating apparatus 400 may use additional equipment such as filters, pumps, pulsation dampers, degassing units, and flow regulators between the container 406 and the slot die 405. In some embodiments, film 410 may be a deposited continuous liquid film. The slot die 405 may have various head sizes and viscosity grades and stripe pattern options. The width of the film 410 may be varied according to the selection of the slot die 405. In some embodiments, film 410 has a width of 1cm to 10 cm. Slot die 405 can be used to control the deposition rate of precursor blend 408 on substrate 404, which affects the thickness of film 410. In some embodiments, a slot die 405 may be used to control the deposition rate of the precursor blend 408 and to inject the precursor blend 408 into the substrate 404. To perform the injection of the precursor blend 408, the substrate 404 is moved under a slot die 405, where the slot die 405 compresses the substrate 404 at the injection location, as shown in fig. 3B. The force applied to the substrate 404 by the slot die 405, the depth to which the slot die 405 compresses into the substrate 404, and/or the deposition rate may be adjusted to tailor the adhesive hydrogel precursor network formed. In some embodiments, the depth of compression is from about 0.02mm to 2mm, in further embodiments from about 0.05mm to about 1mm, in some embodiments from about 0.1mm to about 0.8mm, and in further embodiments from about 0.2mm to about 0.75mm. In other embodiments, the depth of compression is from about 5% to about 30% or from about 5% to about 15% of the thickness of the substrate prior to coating. Those of ordinary skill in the art will recognize that additional ranges of substrate compression within the explicit ranges above are contemplated and are within the present disclosure. The rate of translation of belt 401 may also be adjusted to affect the thickness of film 410. The film 410 may be formed from a single deposited layer of the precursor blend 408 or multiple deposited layers of the precursor blend 408.

In some embodiments, film 410 cools to form coating 412. Typically, coating 412 is a cohesive solid coating, although portions of the substrate may remain uncoated and the coating may have cracks, if desired. Film 410 and/or coating 412 may be dried to remove solvent and/or residual water. The coating apparatus 400 forms a hydrogel precursor patch sheet including a coating 412 on a substrate 404. In some embodiments, the cutting unit 414 is used to cut the hemostatic patch sheet into patches 416. The patch 416 may then be placed into a waterproof package 418.

Fig. 4B is an overview of a process 430 for improving the characteristics of a medical patch using a two-step compression process. In process 430, calendaring substrate 434 is the first compression step. After the step of applying the precursor as melt 438 to the substrate, a second compression step is performed to calender coat the substrate 442. Of course, other process steps may be assembled around the explicit step of fig. 4B, such as additional calendaring steps, cutting steps, drying, sterilization, packaging, and other suitable process steps.

The methods and structures described herein improve the characteristics of medical patches by facilitating the preparation of a substrate for receiving a precursor composition. Step calendaring substrate 434 can help to more consistently apply the precursor in the form of melt 438 to the substrate, and is also typically used for non-aqueous coating, while maintaining a relatively rigid substrate for coating. In general, the step calendaring of substrate 434 can reduce thickness variation of the substrate and can also introduce slight cracking of the cell structure of the substrate. Slight cracking may improve penetration of the precursor into the substrate while maintaining proper stiffness of the substrate, e.g., to avoid bending or warping of the substrate during and/or after the step of applying the precursor to the substrate in the form of melt 438. In some embodiments, the step of calendaring substrate 434 may reduce the thickness of the substrate by up to 65%. In other embodiments, calendared substrate 434 may reduce the thickness of the substrate by 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40%. In some embodiments, the substrate compression caused by calendering substrate 434 is at least partially reversible. In some embodiments, after calendering substrate 434, the thickness of the substrate is partially restored from the fully compressed thickness. In some embodiments, substrate thickness recovery may ultimately result in a final thickness reduction that is 75%, 60%, 50%, 40%, or 25% of the initial thickness reduction. After the step of calendaring substrate 434, the precursor is applied to the substrate in the form of a melt 438, wherein fig. 4A illustrates one embodiment of the step. As described above, the compression during deposition of the hydrogel precursor may be relatively gentle and may result in little or no reduction in the thickness of the substrate after formation of the hydrogel precursor coating. The second compression step (forming the calendered coated substrate 442) is performed after the precursor coating is applied to the substrate and cured. The curing of the precursor layer may occur relatively rapidly by exposure to the environment or optionally by a cooling step. Calendering the coated substrate 442 can impart improved flexibility and hemostatic properties to the coated substrate, for example, by introducing appropriately induced cracks into the precursor coating and by introducing additional cracks into the substrate. In general, the calender coated substrate 442 may also introduce relatively slight to relatively pronounced cracking of the precursor coating. In some embodiments, the fracture comprises a microscale fracture on the surface having a range of widths, lengths, and densities, which may be referred to as fracture to reflect changes in the entire surface. Some of the cracks may be surface cracks and other cracks may have a depth similar to the depth of penetration of the precursor into the substrate. Calendering the coated substrate 442 can reduce the thickness of the coated substrate by up to 65%. In other embodiments, calendaring the coated substrate 442 may reduce the thickness of the coated substrate by 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40%. Those of ordinary skill in the art will recognize that additional ranges of dimensional changes within the explicit ranges above are contemplated and are within the present disclosure.

Steps calendering substrate 434 and/or calendering coated substrate 442 can change the size, shape, and structure of cells/pores within the substrate. In general, process 430 collapses the hole and ruptures the scaffold around the hole. While not wanting to be limited by theory, it is believed that the change in porosity of the substrate upon compression is related to the improved performance of the flexible medical patch. In some embodiments, the process 430 imparts substantial flexibility and other performance improvements to the coated substrate.

Fig. 4C is an illustration of a process flow 450 for manufacturing a patch 487 from a gelatin sheet 451 by a process apparatus. The process device may or may not be configured for continuous processing, with the substrate sheet introduced at one end and the patch withdrawn at the other end. To provide cooling steps, curing steps, etc., the components of the process device may be configured accordingly to allow for these steps, which may take more time than the active processing steps. For convenience, some process components may be configured to continuously perform a subset of the process steps. Of course, steady state process rates may be achieved overall, allowing for efficient use of process instrumentation.

In some embodiments, the gelatin sheet 451 has a thickness of about 0.5mm to about 1.5 cm. In process flow 450, the gelatin sheet 451 is subjected to thermal crosslinking 452 in an oven 453 or other suitable heating device, and the thermal processing unit may also optionally include a control assembly. The oven 453 can be any convenient oven or similar device that houses one or more bright films 451. In general, the gelatin sheet 451 may have any convenient width and length. The thermal crosslinking 452 may be performed at a constant temperature for a selected period of time or may be performed using a selected heating profile. The oven 453 can optionally be integrated with a heater transport system (not shown) that can move the gelatin film 451 at a selected rate to achieve a target heating time or other target heating profile, and the heater transport system may or may not directly interface with other process equipment.

Referring to fig. 4C, after 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 compression 455 of the substrate. In some embodiments, crosslinked substrate 454 has a thickness of about 0.5mm to about 1.5 cm. The substrate compression 455 is performed using calender rolls 456 and 457. Calender rolls 456 and 457 are at a selected distance from each other to form a gap 458. Typically, the gap 458 is less than the thickness of the crosslinked base 454. In some embodiments, gap 458 is no more than 65% of the thickness of cross-linked substrate 454. In other embodiments, gap 458 is 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40% of the thickness of cross-linked substrate 454. The calender rolls 456 and/or 457 may or may not be heated. In contrast to the crosslinked substrate 454, the compressed substrate 459 has a broken cell structure instead of a complete cell structure. In general, compression base 459 is thinner and has a more uniform thickness than cross-linked base 454. In some embodiments, the compression base 459 has a thickness of about 0.25mm to about 1cm, about 0.5mm to about 7mm, about 3mm 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 any convenient conveyor system and the belt 461 may be replaced with a series of rollers or the like. In some embodiments, the calendaring rollers 457 may be part of the conveyor system 460. Those of ordinary skill in the art will recognize that additional ranges of thicknesses and percentages within the explicit ranges above are contemplated and are within the present disclosure.

Next, referring to fig. 4C, the compressed base 459 is coated 462 using the coating apparatus 491. The coating apparatus 491 is similar to the roll slot die coating apparatus 400 of FIG. 4A, except that it is not configured for a roll-based substrate. Container 463 contains a precursor blend 464, which may be a melt blend or an inert organic solvent solution. The precursor blend 464 can be a net mixture of molten precursors. Alternatively, the precursor blend 464 can have one or more additional components to alter the viscosity, such as a non-aqueous solvent. Receptacle 463 can mix and/or heat precursor blend 464 prior to delivering precursor blend 464 through slot die 465 to form film 466 on compressed substrate 467. Coating 462 may use additional equipment such as filters, pumps, pulsation dampers, degassing units, and flow regulators between receptacle 463 and slot die 465. In some embodiments, the film 466 may be a deposited continuous liquid film. Slot die 465 can have various head sizes and viscosity grades and stripe pattern options. Suitable slot die coaters are commercially available. The width of film 466 may be varied by selecting slot die 465 and in general the width may be any reasonable value. In some embodiments, the film 466 has a width of 1cm to 100cm, or in some embodiments, a width of about 2cm to about 20 cm. Slot die 465 may be used to control the deposition rate of precursor blend 464 on compressed substrate 467, which affects the thickness of film 466. The rate of translation of belt 461 may also be adjusted to affect the thickness of film 466. The thin film 466 may be formed from a single deposited layer of the precursor blend 464 or multiple deposited layers of the precursor blend 464. In some embodiments, the film 466 is formed as an adhesive hydrogel precursor network. In some embodiments, the thin film 466 is formed by injecting the precursor blend 464 into the compression substrate 467 while the compression substrate 467 is further compressed at the injection location. In some embodiments, the film 466 cools to form the coating 468. Typically, the coating 468 is a continuous solid coating, although portions of the substrate may remain uncoated if desired. The film 466 and/or coating 468 may be dried to remove solvent and/or residual water. In some embodiments, the coating 468 has a thickness within the ranges described above, which can penetrate into the compressed substrate. In some embodiments, the coating 468 is part of an adhesive hydrogel precursor structure that at least partially penetrates into the compression substrate 467. In some embodiments, the coating 468 is part of an adhesive hydrogel precursor structure having a surface that conforms to one surface of the compression substrate 467. In some embodiments, a cutting unit 469 is used to remove the anterior segment 470. Removing the anterior segment 470 may provide a more uniform coating on the patch 487.

Next, a coated substrate 471 having a coating 472 and a compressed substrate 473 is subjected to a coated substrate compression 476 to form a compressed coated substrate 477. The coated substrate compression 476 may be performed using calender rolls 478 and 480. Calender rolls 478 and 480 are at a selected distance from each other to form gap 481, as shown in fig. 4D. Typically, gap 481 is less than the thickness of coated substrate 471. In some embodiments, gap 481 may not exceed 75% of the thickness of coated substrate 471. In other embodiments, gap 481 is 15% to 70%, 20% to 65%, 22% to 62%, or 30% to 60% of the thickness of coated substrate 471. In some embodiments, the compression coated substrate 477 has a thickness of about 0.3mm to about 1cm and in other embodiments about 0.5mm to about 5 mm. Calender rolls 478 and/or 480 may or may not be heated. The compression coated substrate 477 has a break coating 482 and a compression substrate 483. In general, the compression coated substrate 477 is thinner and more flexible than the coated substrate 471. In some embodiments, the burst coating 482 has microcracks of various widths, lengths, and depths substantially across the surface to present a burst surface. In some embodiments, the break coat 482 has a relatively uniform break surface area to total surface area ratio over a majority of the surface area. In some embodiments, the edges of the breakaway coating 482 are different from other areas of the breakaway coating 482. In some embodiments, the break coat 482 has a thickness of from about 0.1mm to about 8mm, from about 0.15mm to about 7mm, from about 0.2mm to about 5.5mm, from about 0.25 to about 5mm, from about 0.35mm to about 4.5mm, and in some embodiments, from about 0.5mm to about 4 mm. In some embodiments, compression substrate 483 has a thickness of about 0.1mm to about 9mm, about 0.15 to about 8mm, about 0.25mm to about 6mm, about 0.5mm to about 5.5mm, about 0.75mm to about 5mm, and about 1mm to about 4 mm. In some embodiments, the coated substrate compression 476 is integrated with a conveyor system 460 having a belt 461, the conveyor system 460 also conveying the substrate through the substrate compression 455. In some embodiments, calender roll 480 may be part of conveyor system 460.

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

The processing may be performed in a controlled atmosphere, such as under dry nitrogen, other inert gases, and the like. After the patch is formed, it may be packaged under dry inert gas in moisture-proof packaging, such as a polymer and/or foil pouch, and the like. The patch may be heated, such as from 40 ℃ to 90 ℃, for further drying. A package of desiccant may be included in the package to help maintain dryness. The patch may be sterilized, for example, by the use of radiation after packaging. Sterilization may be performed without causing substantial cross-linking. The package is appropriately marked according to regulatory guidelines for medical use and the expiration date is indicated.

The storage of the patches is typically done in moisture-proof packaging. In some embodiments, the patch is heat sealed into a foil pouch. To increase the storage time, it may be desirable to store the patch under refrigerated conditions. Typically, the patch may be stored at a temperature of no more than about 5 ℃, or at standard refrigerator temperatures, which may be in the range of 1 ℃ to 7 ℃, although lower temperatures may be used as desired. For short term storage, the patch may be stored at room temperature. The patch may be stored for at least 2 months, in further embodiments for at least one year, in further embodiments for three months to 3 years, and in some embodiments for 6 months to 2.5 years at refrigeration temperatures. Those of ordinary skill in the art will recognize that additional ranges of storage temperatures and times within the explicit ranges above are contemplated and are within the present disclosure. Patches exceeding their shelf life can be identified by insufficient adhesion due to premature crosslinking or removal of electrophilic groups for crosslinking due to premature hydrolysis.

Biological agent and medicine

In addition to the optional imaging agent, the patch may also contain a biologic. The optional biological agent or drug may be, for example, an agent that promotes blood clotting and/or healing. Although good hemostatic function has been achieved without complicating the addition of blood products to the patch composition, thrombin may be added to the patch. Because the patch material absorbs rapidly, the patch may degrade before any significant problems associated with adhesion formation or microbial contamination occur. However, if desired, an antimicrobial agent may be added. In further embodiments, the therapeutic agent may include an analgesic, anesthetic, steroid, antibiotic, steroid, anti-infective agent, anti-inflammatory agent, non-steroidal anti-inflammatory agent, antiproliferative agent, or a combination thereof. These approaches can be effectively used for topical drug delivery because the patch provides local adhesion as well as a reservoir of added drug or bioactive agent.

Use of patches and medical indications

The medical patches described herein are particularly useful as hemostatic patches. Hemostatic patches are applied with compressive force to the site of little, mild or moderate bleeding, with the goal of stopping bleeding. The patch may or may not include a therapeutic agent, such as a compound that promotes clotting, and the examples demonstrate effective hemostasis without any bioactive agent. Patches may be more generally used in contact with exposed tissue without having to attempt to control significant bleeding, such as for surgical closure applications. The cross-linking activation of the patch is induced upon contact with any biological fluid. With the appropriate substrate and thickness, the patch may be relatively flexible and conformable even when dry, and this property may be useful in certain applications.

In general, patches may be delivered directly onto a wound site, such as in open surgery. In alternative embodiments, the patch may be used for laparoscopic surgery because the patch is flexible enough to be delivered through a trocar. While it may be convenient to apply the patch to the wound with the hydrogel precursor layer facing the wound, alternatively the patch may be folded, for example with the hydrogel precursor layer facing outwards, and inserted into the wound so that the patch fills the wound.

To provide further patch delivery options, fig. 13A shows patch 750 that has been folded into a loose accordion-like shape. Fig. 13B shows a procedure 800 wherein an accordion folded patch 801 is introduced into a cannula 803 by forceps 805. The process 800 may be used to guide an accordion folded patch 801 to a treatment site. Fig. 13C shows an embodiment in which patch 806 has been accordion folded and then folded laterally. Fig. 13D shows a procedure 810 in which an accordion folded and laterally folded patch 812 is introduced into a cannula 814 by forceps 816. The process 810 may be used to guide an accordion folded and laterally folded patch 812 to a treatment site. In some embodiments, the process 800/810 may be used to preload the cannula 803/814 for future use. In some embodiments, the process 800/810 may be used to preload the cannula 803/814 for packaging as a "preloaded" patch. In some embodiments, the procedure 800/810 may be used with a tubular applicator in place of the cannula 803/814. Patch 750 and patch 806 each provide a more compact shape than a flat patch, which may be convenient for certain applications such as laparoscopic surgical applications.

Fig. 14 is a schematic view of patch delivery for laparoscopic surgery 820, wherein an accordion-folded patch 824 has been introduced into laparoscopic site 831 through cannula 826 using forceps 828. Forceps 830 have been introduced through cannula 834 into laparoscopic site 831. Forceps 830 may help guide accordion folded patch 824 to treatment site 838. In some embodiments, the treatment site 838 may be a wound site or a surgical site ready to be closed. In some embodiments, the accordion folded patch 824 may be used in laparoscopic surgery 820 to provide hemostasis. In some embodiments, the coating of the accordion folded patch 824 may break at the fold line. In some embodiments, cracks in the coating of the accordion folded patch 824 may extend to the substrate surface. Generally, the accordion folded patch 824 may self-repair the crack due to swelling when hydrated by fluid at the treatment site.

Hemostatic patches may also be ground or chopped as needed to serve as a filler, alone or in combination with another patch or portion of a patch. The chopped patch preparations or similar particulate compositions described above may be dispensed through a cannula attached to a bellows-type device. Such formulations may be used to seal or control bleeding from large areas of exuded surfaces of tissue.

In some embodiments, the patch may be wetted with a sterile aqueous solution (such as saline or water for injection) to initiate hydration shortly before application of the patch to tissue. Typically, the patch is applied to tissue with a sterile gauze pad or the like placed on the patch surface to facilitate the application process, and as used herein, gauze pad refers to a pad of any non-adhesive absorbent material. A gauze pad may be used to apply a substantially uniform pressure to the patch over a period of time to allow for adhesion. The time selected 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 of ordinary skill in the art will recognize that additional ranges of times within the explicit ranges above are contemplated and are within the present disclosure. Placement of the patch may include using a single patch or placing multiple medical patches over a bleeding defect. The additional medical patch may overlap at least a portion of the first medical patch.

For wounds, bleeding can be stopped by using patches in a process called hemostasis. Hemostasis involves coagulation such that bleeding ceases and can be considered the first stage of wound healing. After hemostasis, the wound no longer bleeds. With the patches described herein, hemostasis can generally be achieved in about 5 minutes, and in some embodiments, in no more than 3 minutes. Those of ordinary skill in the art will recognize that additional ranges of hemostatic times within the explicit ranges above are contemplated and are within the present disclosure.

Specific uses of interest include application of the patch to a wound on or in an organ or to a wound on a blood vessel. In a broad sense, hemostasis may involve any wound repair, although the extent of bleeding may vary significantly. The patches described herein may be used in cases of any degree of bleeding, but as shown in the examples they may be effective in cases of massive bleeding. In the case of surgery, the patch may be used for placement in surgery involving blood vessels, liver, intestinal tract, uterus, pancreas, other organs, orthopedic applications (such as bones and connective tissue) or generally any surgical wound and wounds resulting from injury. In some embodiments, the patch may be placed along the skin to close a wound on the patient surface or to end a surgical intervention.

While generally any tissue wound may be effectively covered with the patch described herein, the patch is particularly effective for covering wounds in organs that are prone to massive hemorrhage. 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 be generally natural, transplanted, or a combination thereof. In particular, the patch may be applied to a bleeding defect. The bleeding defect may be, for example, a suture, a puncture, a gunshot wound, a cavity, an abrasion, a biopsy puncture, a graft interface, or a combination thereof. Placement of one or more patches may include placing one or more medical patches in a non-planar geometry over the bleeding defect, which is generally determined by the shape of the organ. Placement of the patches may include wrapping one or more medical patches around the organ. The extent of organ bleeding may be assessed according to a spot grade bleeding score or other validated bleeding scale.

In some embodiments, the patch itself may be wrapped in a pre-folded form, as shown in fig. 13A and 13C, or in a "pre-loaded" form, allowing deployment from a tubular applicator using a mandrel or plunger-like mechanism to squeeze the patch into proximity to the treatment site. Preloading of patches is used for laparoscopic applications, where insertion through a narrow tubular portal is involved, and the patch may be moved further to the hemostatic site after introduction through a laparoscopic manipulator, which may also apply pressure to rest the patch against the wound. In other embodiments, pre-loaded configured deposit wrap patches or cylindrical patches may be delivered to defects (such as bullet wounds or puncture wounds) where hemostasis by flat substrate geometries is less desirable. In further embodiments, the preformed patch-mandrel relationship may provide a geometry for delivering a less than ideal hemostatic using a flat patch, wherein the mandrel surface has a desired shape for conforming the patch to a wound.

One application envisaged is to fit a conical preformed patch with a conical mandrel for hemostasis after cervical tissue ring electrotomy (LEEP). In this case, the shape of the mandrel and preformed patch acts to fill the irregular tapered depression left by LEEP surgery, and the patch adheres and reaches hemostasis after which the mandrel can be removed. Fig. 12A and 12B show one embodiment of the above application. Fig. 12A shows a conical hemostatic patch 700 placed into a cervix 704 using a conical mandrel 702. Fig. 12B shows hemostatic patch 710 disposed within cervix 704. The left inset shows that tapered mandrel 702 provides pressure for a tapered hemostatic patch within cervix 704. The right hand inset shows the irregularly tapered depression with the tapered mandrel 702 removed and the disposed hemostatic patch 710 adhered to cervical tissue. For this and similar shaped embodiments, the patch may be heated to soften the precursor layer for shaping into a mandrel or simply otherwise molding into the desired shape. If cooled on the mandrel, the shape may be substantially maintained for deployment.

In further embodiments, the patch becomes soft and conformable by processing or pre-wetting, and may be applied to additional gynecological applications. Certain embodiments use a conformable patch to stop bleeding from hysterectomy after delivery by caesarean section. In another application, the softening patch may be applied transcervically to stop post-partum bleeding. Postpartum hemorrhage can be a very alarming condition that causes rapid loss of blood to the mother, resulting in blood pressure drop and shock, possibly leading to death. In some cases, after therapeutic treatment and manual hemostasis by compression failure, the softening patch can be delivered vaginally/transcervically and conform to irregular intrauterine surfaces, eliminating more extreme consequences of surgical intervention, hysterectomy, or death. Desirably, the patch will rapidly stop bleeding within 1-2 minutes and will then rapidly absorb to reduce interference with any additional future medical diagnosis. Multiple patches may be used until hemostasis is achieved.

Although in some embodiments the patch is wetted shortly before delivery to the application site, the one or more patches may be placed without prewetting the one or more medical patches. In some embodiments, placing the one or more patches includes wetting the one or more medical patches with non-buffered water or non-buffered saline before and/or after placement. Whether or not the patch is pre-moistened, the patch hydrates relatively quickly. As the precursor crosslinks to form the hydrogel, the precursor layer becomes adhered to the application site. Typically, the precursor layer hydrates and adheres to the organ or other tissue in no more than about 2 minutes.

The ocular application may involve a patch having a substrate for preventing the reactive precursors from adhering to the applicator or user during application to the moist ocular surface. In certain embodiments, the substrate dissolves rapidly, or is removable, such that it is present only for a time sufficient to prevent adhesion during application. In other embodiments, the substrate is non-resorbable, continues to provide structural support to the blended melt precursor, and is removed after application of the precursor. It is contemplated that the ophthalmic application will contain a premixed precursor melt of a therapeutic agent for treating an ocular surface condition, such as controlling postoperative pain, and/or treating the anterior chamber of the eye. In such embodiments, the molten precursor plus therapeutic agent may be applied to the ocular vault using a releasable backing and then removed after crosslinking begins. In some cases, the melt blend of precursors may be less compatible with the substrate to reduce adhesion to the substrate during application. In other cases, the melt precursor is preformed, cut into an insertion shape, and the substrate backing is added after or just prior to application. Where the substrate is added after the unreacted blend is produced, an adhesive (such as a low Mw PEG liquid) may be used to enhance the adhesion of the melt blended precursor to the substrate during storage or shortly before application. One embodiment may include a melt precursor wafer attached to a disposable applicator substrate that may be applied to the ocular vault by the patient and then discarded (substrate).

From this embodiment, where the patient is self-administered, the various therapeutic agents may be delivered in sufficiently large amounts over a potentially shorter period of time. The greater therapeutic loading enables the use of a greater class of less potent drug substances. High potency candidates are one limitation of ocular implants, which are limited to small volume applications such as punctal plugs, anterior, posterior, and suprachoroidal injections. One example is topical vault delivery using NSAIDs or bupivacaine, rather than using highly potent corticosteroids, which can present off-target problems such as elevated intraocular pressure resulting from prolonged use. In these embodiments, only highly potent therapeutic agents are no longer needed, opening the way for ocular applications in the anterior part of the eye, such as the treatment of painful inflammation, dry eye, infections, and the like.

In the case of surgery, patches typically provide the required burst strength, but sutures may also be applied, for example dissolving sutures, if desired. For degradable patches, the applied patch can be sealed inside the patient and safely degraded at the appropriate time to achieve hemostatic stabilization. Typically, no further intervention of the patch is required, but in rare cases, additional care may be applied to the wound. For in vivo use, the patch is typically taken in vivo for removal by desorption, typically by the kidney, is completed within 28 days, in further embodiments within 21 days, and in further embodiments from 7 days to 14 days. Those of ordinary skill in the art will recognize that additional ranges of times within the explicit ranges above are contemplated and are within the present disclosure. In alternative embodiments, the patch may be designed such that the hydrogel is substantially non-absorbable so that it may last for an extended period of time.

Fig. 5 is a schematic view of a hemostatic patch 501 wrapped around a tubular organ 504. In some embodiments, tubular organ 504 is an artery or vein. The wrapped hemostatic patch 501 may have a tail 506 formed by connecting two ends of the hemostatic patch 501. The hemostatic patch 501 may be dry, or pre-moistened, prior to wrapping. Examples 5 and 6 illustrate wrapping sutures on the femoral artery with hemostatic patch 501. Example 6 illustrates a hemostatic patch 501 wrap using a double layer of wet gauze and hemostatic patch 501. As exemplified in example 5, the hemostatic patch may be placed over the tubular organ and/or over the tubular graft without wrapping. Example 6 illustrates a non-wraparound procedure for establishing hemostasis in a luminal bone defect using a disc-shaped hemostatic patch.

Fig. 6 is a schematic view of a hemostatic patch 512 placed over a non-tubular organ 514. Examples 3 and 4 illustrate placement of hemostatic patch 512 on a liver defect including concave and convex defect surfaces. Fig. 7 is a schematic view of a hemostatic patch 518 placed on skin 520.

Fig. 8A-8D illustrate the method of action of the hemostatic patch. Fig. 8A shows a bleeding defect 600 of tissue 604 from which blood 606 flows. Fig. 8B shows hemostatic patch 607 placed over tissue 604. Hemostatic patch 607 is placed with base 608 facing away from bleeding defect 600 and melt blend layer 610 facing bleeding defect 600. Blood 612 from the bleeding defect 600 is drawn into the hemostatic patch 607, thereby dissolving and interacting the precursors in the melt blend layer 610 to form a crosslinked hydrogel layer 616 (fig. 8C). In some embodiments, after placement of the hemostatic patch 607 over the bleeding defect 600, the melt blend layer 610 reacts to form a crosslinked hydrogel layer 616 within 30 seconds. Fig. 8C also shows that the substrate 618 is conformable to allow the hemostatic patch 620 to adhere to tissue 622 and to occlude the bleeding defect 600 to result in a hemostatic defect 624. Fig. 8D shows the healed tissue 626 in which the hemostatic patch 620 has been absorbed.

Examples

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

Example 1 preparation of hemostatic Patch samples

This example describes the preparation of hemostatic patch samples.

Hemostatic patch samples were prepared by melt coating a dried blend of two hydrogel precursors onto a porcine gelatin substrate. Various gelatin/collagen substrates as shown in table 1 were prepared. Each substrate is crosslinked, wherein light crosslinking means less than about 20% crosslinking and high crosslinking means greater than about 20% crosslinking. Substrates A, B and D are characterized as having small pores (micron-sized or smaller) and a porosity of greater than 80%, as measured by mercury intrusion porosimetry. Each substrate was prepared for coating by drying in an oven at a temperature of 35 ℃ under ambient air for 18 hours or until the relative humidity of the oven was less than 5%. The thickness of the gelatin substrate after drying was approximately the same as the thickness before drying. For each patch sample, the first hydrogel precursor was an eight-arm polyethylene glycol-based precursor having a molecular weight of 15,000da and Succinimidyl Glutarate (SG) functional end groups (8A15k PEG SG,Jenkemusa). The second hydrogel precursor is an eight-arm polyethylene glycol-based precursor having a molecular weight of 20,000da and an HCl salt amine functional end group (8 a20k PEG amine-HCl, jenkemusa). The first and second precursors were measured as powders and then melt blended with traces of FD & C Blue #1 in a heated roller system at a temperature above 45 ℃ in a glove box. The molten precursor blend was delivered to a liquid distribution system (Vulcan ^TM Jet Dispenser, nordson). A monolayer of the coating of the melt blend was applied to a dry gelatin substrate under inert gas conditions with a width of 0.5mm per pass and a line speed of 50 mm/sec until the total width of the coating was about 20cm. The thickness of the coating was about 0.25mm. The mixed precursor coated substrate is cured at room temperature under inert gas conditions. The thickness of the resulting coated substrate was measured to be about 1.25mm. The coated substrate was cut into individual hemostatic patches of about 2 x 4cm in size and packaged in foil containers or disposable bags, both designed to maintain an initial relative humidity of the inert gas in the container below about 20ppm. Suitable commercial medical packages include Amcor PerfecFlex 35772-E or Paxxus Symphony-1010. Packaging, and sterilizing the patch. The mixed precursor coated side ("active side") of each patch is identified by its blue coloration, while the base backing on the other side of each patch is free of blue coloration.

TABLE 1

Example 2 in vitro testing of hemostatic Patch samples and substrates

This example evaluates the gel time, burst pressure, swelling and persistence of a set of hemostatic patches prepared according to example 1. This example also evaluates the swelling and persistence of the substrate.

Part a. Test samples and test procedures. A hemostatic test patch prepared according to example 1 using substrate type a ("test patch a") was used in this study. Separately, the (uncoated) samples of substrate a and substrate D, having low and high cross-links, respectively, were also tested. Individual samples for testing were cut from either the monolithic test patch a or the monolithic substrate a or substrate D. The test methods used in this example are described in the "hydrogel and patch properties" section above.

And B, testing the substrate.

The swelling of the samples of substrate a was evaluated. The sample of substrate a was weighed and then immersed in Phosphate Buffered Saline (PBS) solution maintained at 37 ℃ for a selected period of time. Tables 2-4 show sample swelling at 30 seconds, 1 minute and2 minutes, respectively. The swelling of the samples at 30 seconds, 1 minute and2 minutes were average 814 wt%, 973 wt% and 1053 wt%, respectively. The results indicate that biocompatible substrates can be prepared with high swelling rates and high swelling levels at 30 seconds.

TABLE 2

TABLE 3 Table 3

Sample of	Mass g	Swelling at 1 min
			1	0.0071	887%
2	0.007	1017%
			3	0.0073	892%
4	0.0073	1049%
			5	0.0066	1018%
Average value of	0.07568	973%

TABLE 4 Table 4

Sample of	Mass g	Swelling at 2 minutes
			1	0.0068	1103%
2	0.0069	1077%
			3	0.0068	1000%
4	0.0072	993%
			5	0.0074	1092%
Average value of	0.08094	1053%

Samples of substrates a and D were evaluated for persistence in PBS solution. The samples were immersed in a PBS solution maintained at 37 ℃. 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 substrate a sample (samples 1-10) was observed to partially persist after 67 hours. Samples 1-10 were not visible at 96 hours, indicating a persistence window for substrate a of about 2.8 to about 4 days. Each substrate B sample (samples 11-15) was observed to last after 114 hours.

The results show that substrate sustainability in an in vivo environment can be well controlled by substrate processing. The results also show that biocompatible absorbable substrates with high water absorption and total water absorption have been prepared and that these highly absorbent substrates can be designed to last within a controlled time window.

TABLE 5

And C, testing the patch.

Patch samples were cut from a single 2x 4cm test patch a into 8mm discs using an 8mm biopsy punch.

Gel times of patch samples were evaluated using a commercial texture analyzer as described in the "hydrogel and patch properties" section above. Fig. 11 shows a typical force versus time curve for patch samples evaluated immediately after activation with pH 8 buffer solution. The arrow in fig. 11 indicates the time corresponding to the lowest force on the curve. The gel time of this sample was measured to be 25 seconds.

After gel time testing, patch samples were tested for burst pressure. The burst pressure results are shown in table 6. The burst pressure of sample 1 was recorded as 0, indicating that the sample did not adhere to the test block after the gelation test. Samples 2-5 have burst pressures of 10 to 65mm Hg. Samples 6-10 have burst pressures greater than 140mm Hg, with sample 9 having a burst pressure of 188.2mm Hg. Table 6 also shows the mass of the patch samples before and after burst testing. Swelling of the patch samples during burst testing ranged from about 340% to about 510%.

TABLE 6

Following the burst test, the patch samples were evaluated for persistence and swelling from a hydrated state following the burst test. The results are summarized in table 7. Samples 1-5 were immersed in a PBS solution maintained at 37 ℃. These samples had an average swelling of 203 wt% over 24 hours. Since this expansion after hydration was achieved at the end of the burst test, the cumulative swelling of patch samples 1-5 from the dry state after about 24 hours was determined to be 1412% to 1903%. Samples 1-5 were not visible after 114 hours (4.8 days). Samples 6-10 were immersed in a PBS solution maintained at 50 ℃. In this accelerated aging study, each sample had almost disappeared at 24 hours.

TABLE 7

"X" indicates that the sample has almost disappeared

The results show that biocompatible absorbable patches have been prepared with gel times less than 30 seconds and burst pressures exceeding 140mm Hg. These patches have also been shown to have a relatively high rate of swelling and overall degree of swelling, but a relatively short duration (less than about 5 days). The results show that the test patch has similar persistence compared to the detached substrate (substrate a). The results indicate that the precursor layer and the substrate can be tailored such that the persistence of both the resulting hydrogel layer and the substrate is similar. Alternatively, the precursor layer and/or substrate may be tailored such that the resulting hydrogel layer or substrate has a shorter duration.

EXAMPLE 3 liver defect study 1 (with comparative example)

This example evaluates the hemostatic effect of the hemostatic patch prepared according to example 1 in a porcine liver defect model. Comparison was made with commercially available fibrin sealant patches.

Part a. Test and control patches. The study used three hemostatic test patches prepared according to example 1 using substrate type a ("test patch a"), substrate type B ("test patch B") and substrate C ("test patch C"), respectively. Comparative fibrin sealant patch ("control patch a") from Baxter was purchased @Fibrin sealant patch, 0.5cm x 4.8cm, product code 1144922). Each patch was trimmed to approximately 2 x 2cm size for application. The active face of the test patch was blue and the active face of the control patch was yellow.

And B, preparing an animal defect model. An acute (yokexia) pig was cut along the anterior (ventral) midline and the liver was isolated. The animals had the following characteristics of body weight (48.2 kg), sex (M), anticoagulation (ACT: 242). ACT is recorded prior to first placement. Both left and right inner lobes of the liver produce defects. The liver was penetrated to a depth of about 4mm using an 8mm biopsy punch. Mei Zengbao (Metzenbaum) scissors were then used to remove the emboli generated by the penetrator. At this point, bleeding was assessed using the Adam scale, described in Adams et al, journal of Thrombosis and Thrombolysis (2009) 28:1-5 (DOI 10.1007/s 11239-008-2049-3), incorporated herein by reference. According to Adam scale, a target bleeding score >3 is ideal. (see FIG. 9). If the target score is not reached, the liver is penetrated again using the biopsy punch until the target score is reached. The defective bleeding score generated for each trial was recorded as the initial score as shown in tables 8 and 9. Test patch A bleeding defects were severe (runs 2-1 and 2-2), moderate (runs 2-3) and mild (runs 2-4). Control patch A showed severe (runs 2-1C and 2-2C), moderate (runs 2-3C) and mild/moderate (runs 2-4C) bleeding defects. Prior to placement of the patch, the defect site bleeding was treated with clean dry gauze.

TABLE 8

Test patch A test	Initial scoring	Scoring at 1 minute	Scoring at 3 minutes
				2-1	4	0	0
2-2	4	0	0
				2-3	3	0	0
2-4	2	0	0
				Average value:	3.25	0	0

TABLE 9

Control patch A test	Initial scoring	Scoring at 1 minute	Scoring 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 value:	3.2	1.8	2.3

* There is swelling under the patch.

Part C. Patch evaluation procedure and results. Clean gauze was moistened with clean sterile saline. The test patch a sample was placed back down on a wet gauze with the active side of the patch facing away from the gauze, although in general use, the patch could be placed without the gauze to facilitate proper placement, and then the gauze could be used to maintain a certain pressure while the patch is adhered. The gauze used to treat the bleeding at the defect site is removed from the defect site. The patch is placed on the defect site immediately so that the active side of the patch is in contact with the defect and as centered as possible in the defect. With the hands open, a strong and uniform pressure was applied with a wet gauze on the back side of the patch and held for 1 minute (first interval). The pressure was then slowly reduced and the gauze carefully removed from the back side surface of the applied patch. If there is any adhesion of the gauze to the patch, a clean surgical instrument is gently applied to the edge of the patch, or gentle rinsing is used to separate the gauze from the patch while minimizing interference. After the 30 second evaluation period, a 1 minute bleeding score was recorded according to Adam scale, as shown in table 8. A strong and uniform pressure was then applied again to the back side of the patch using wet gauze for an additional 2 minutes. The pressure was slowly reduced again and the gauze was carefully removed from the back side surface of the applied patch. After the 30 second evaluation period, a 3 minute bleeding score was recorded according to Adam scale, as shown in table 8. Then, the edge of the patch was gently lifted using a pair of tweezers to test adhesion. The procedure was repeated with test patch a for the other three defects for a total of four trials. All test patch samples adhered well to the target site and were not affected by wet gauze removal. In addition, the edges of the test patch samples were not pulled up when pulled/picked with forceps. No leakage through any of the test patch samples was observed. The results indicate that all experiments using test patch a achieved hemostasis within 1 minute after placement.

The procedure described above was repeated for control patch a, with some modifications. For control patch A runs 2-3 and 2-4, the target bleeding score was reduced from >3 to >2 due to poor performance of the control samples in runs 2-1C and 2-2C. The results are shown in table 9. For control patch a trials 2-4C, the bleeding score was recorded as 03 minutes after placement, but there was swelling under the patch. Upon compression, blood flows out from under the patch and continues to bleed. The test is considered to be non-hemostatic. The results indicate that although the target bleeding score was reduced for the latter two trials, none of the trials with control patch a achieved hemostasis 3 minutes after placement. Furthermore, it was observed that the control patch a sample did not adhere to the target site and it was easily detached. During removal of the wet gauze, extreme care is required so as not to disturb the patch from the placement site.

Test patch B and test patch C were evaluated separately on liver defects generated by trials 2-2C and 2-3C on control patch a, after these control patch samples continued to develop severe or slight bleeding at 3 minutes, respectively. Two test patch samples were able to resume hemostasis in 1 to 3 minutes as shown in table 10. The initial placement of test patch B was not centered in the defect. A second test patch B was placed at the defect 1 minute after initial placement. Hemostasis was achieved 3 minutes after initial placement (corresponding to 2 minutes after second placement).

Table 10

Sample of	Initial scoring	Scoring at 1 minute	Scoring 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 the second test patch B was placed at 1 minute.

Part D. Additional patch evaluation. In addition, test patch a was further evaluated by non-planar placement into defects created on the liver surface using a scalpel. The channel defect is about 3mm deep and about 5mm long. Test patch a was cut to a size of 2x 4cm, wetted with saline, folded in half longitudinally and then placed into the defect. Fig. 10A shows the test patch a after initial placement. Pressure was applied to the test patch samples using a moistened gauze sheet. Hemostasis was achieved at 1 minute at the site of the test patch contact defect, as shown in fig. 10B. Fig. 10B also shows that areas of the defect not in contact with the test patch continue to bleed.

This example shows that the hemostatic patch prepared according to example 1 is significantly better than the commercially available fibrin sealant patches, achieving hemostasis 1 minute and 3 minutes after placement at a porcine liver defect. Reactive precursors in hemostatic patches allow for flat placement and non-flat placement, and allow for manual compression for a short time after placement, resulting in a rapid, adaptable and easy to use patch for mild to severe bleeding defects of the liver.

EXAMPLE 4 liver defect study 2 (with comparative example)

Part a. Test and control patches. A set of hemostatic test patches ("test patch a") prepared according to example 1 using substrate type a was used in this study. Johnson and Johnson comparative seal patch with embedded human fibrinogen and human thrombin ("control patch B"). Purchased @Fibrin sealant patch, 5.1cm×10.2cm, product code EVT 5024). Each patch was trimmed to approximately 2 x 2cm size for application. The active face of the test patch was blue and the active face of the control patch was yellow.

And B, preparing an animal defect model. An acute (yokexia) pig was cut along the anterior (ventral) midline and the liver was isolated. The animals had the following characteristics of body weight (57.4 kg), sex (F), anticoagulation (ACT: 294). ACT is recorded prior to first placement. Both left and right inner lobes of the liver produce defects. The liver was penetrated to a depth of about 4mm using an 8mm biopsy punch. Mei Zengbao (Metzenbaum) scissors were then used to remove the emboli generated by the penetrator. At this time, bleeding was evaluated. According to Adam scale, a target >3 is ideal. (see FIG. 9). If the target score is not reached, the liver is penetrated again using the biopsy punch until the target score is reached. The defective bleeding score generated for each trial was recorded as the initial score as shown in tables 11 and 12. All test patches a were severe with bleeding defects. Control patch B showed moderate (trial 3-1C) or severe (trials 3-2C, 3-3C and 3-4C) bleeding defects. The defect site bleeding was treated with clean dry gauze.

TABLE 11

Table 12

* During hemostatic examination, the patch falls off with the gauze.

* The patch then falls off and the wound requires re-treatment.

Part C. Patch evaluation procedure and results. This example follows the procedure described in section C of example 2, with the modification that the first scoring is performed after 30 seconds. All test patch a samples adhered well to the target site and were not affected by wet gauze removal. In addition, the edges of the test patch a samples were not pulled up when pulled/picked with forceps. No leakage was observed through any of the test patch a samples. As shown in table 11, all experiments using test patch a achieved hemostasis within 30 seconds after placement.

The results of control patch B are shown in table 12. Only one control patch B sample (control patch B test 3-4C) achieved hemostasis after 3 minutes. However, at the later stage of the study, the patch was shed and bleeding restarted. The detached patch is later located in the chest. The other three control patch B tests showed exudation (control patch B tests 3-1C and 3-2C) or moderate bleeding (control patch B test 3-3C) at 3 minutes. During removal of the wet gauze, extreme care was required to not interfere with the control patch. At the time of evaluation at 3 minutes, it was observed that control patch B adhered to the wound only in the location of active bleeding. The control patch area beyond the wound did not adhere to the tissue and remained as a loose/raised flap.

Part D. Additional patch evaluation. In addition, test patch a was further evaluated using multiple non-planar (convex) placements on partially resected liver lobes. Placed are pre-moistened 2X 4cm patches, 2X 4cm dry patches and 2X 2cm dry patches. Less difficulty in applying pressure to the dry patch was observed compared to the pre-moistened patch because of less sliding. After placement of all three patches, hemostasis of the entire defect was achieved. Each placement achieves hemostasis in the area of contact with the corresponding patch.

This example shows that the hemostatic patch prepared according to example 1 is significantly better than the commercially available fibrin/thrombin sealant patch to achieve hemostasis for moderate to severe bleeding 30 seconds, 1 minute and 3 minutes after placement at a porcine liver defect. Although fibrin/thrombin blocking patches have reactive substances (thrombin), the patches do not actually block wounds as hemostatic patches. Peel tests of the hemostatic patch edge showed no delamination, whereas the fibrin/thrombin patch was attached only to the wound site. In two of the four trials, the control patch had fallen off.

EXAMPLE 5 cardiovascular defect study

This example evaluates the hemostatic effect of hemostatic patches prepared according to example 1 after various placements in a porcine cardiovascular defect model.

Part a. Test patches. A set of hemostatic patches ("test patch a") prepared according to example 1 using substrate type a was used in this study. All placements were made with the patch dry. After placement, the patch is made flexible by hydrating the patch directly with saline or by applying pressure with pre-moistened gauze.

And B, preliminarily preparing an animal defect model. The study used a 60kg sow in acute (york summer). An incision is made in the skin on the ventral midline of the neck to expose the carotid artery. Blunt dissection was performed through underlying subcutaneous tissue and muscle. The muscle is retracted and fascia surrounding the target vessel is dissected from the vessel surface. The side branch of the vessel was ligated with silk suture material and clips. After proximal and distal control of the artery is obtained using the vascular ring and vascular clamps, the vessel is temporarily occluded. An arteriotomy is performed and the graft material (Gore Acuseal) is anastomosed in an end-to-end fashion using a non-absorbable suture. After anastomosis is completed, blood flow is reestablished by removing the vascular ring and vascular clamp.

A inguinal incision is made to expose each femoral artery. Blunt dissection was performed through underlying subcutaneous tissue and muscle. The muscle is retracted and fascia surrounding the target vessel is dissected from the vessel surface. The side branch of the vessel was ligated with silk suture material and clips. After proximal and distal control of the artery is obtained using the vascular ring and vascular clamps, the vessel is temporarily occluded.

Part C defect creation, patch procedure and results.

Procedure 1 femoral artery placement. The blood flow was stopped at the 3-5cm portion of the left femoral artery using a clamp and vascular ring. 4 vascular punctures were performed using a 25 gauge needle to simulate the suture of a vascular repair procedure. The arteries were loosened to ensure that bleeding defects had occurred, and bleeding was rated using Adam's scale. Pulsatile bleeding was determined to be severe (Adams scale rating 4). The artery is re-clamped to stop blood flow and the area is cleared of blood build-up. Test patch A was cut to about 1X 1.7cm. The dry test patch was placed on top of the defect site in a manner to cover the defect with the blue side bleeding toward the target. Manual pressure was applied to the test patch using a pre-moistened gauze sheet for 30 seconds. Blood flow in the region is then restored by removing the vascular ring and the clamp. After manual pressurization for 30 seconds, the gauze was removed. The patch was evaluated for hemostasis and adhesion. Arterial blood flow was confirmed by examining the pulse on both sides of the placed patch. It was observed that the site stopped bleeding 30 seconds after patch placement and good adhesion to surrounding tissue was achieved. About 1 hour after placement, the hind leg was "mobilized" to simulate movement. During and after this movement, the patch remains adhered to the defect and surrounding tissue. Pulses were found on both sides (distal and proximal) of the placed patch.

Procedure 2 femoral artery placement during pulsatile flow. The procedure was performed at the same site as described in procedure 1, using No. 25 for one puncture of the vessel proximal to the defect in procedure 1. Pulsatile puncture bleeding was determined to be severe (Adams scale rating 4). The puncture is immediately covered with manual pressure until the patch is about to be placed. The manual pressure was removed and a dry patch of approximately 1.5 x 2cm size was immediately placed on top of the active bleeding site. Manual pressure was applied to the patch using a pre-moistened gauze sheet for 30 seconds. After manual pressurization for 30 seconds, the gauze was removed. The patch was evaluated for hemostasis and adhesion. Arterial blood flow was confirmed by examining the pulse on both sides of the patch placed. It was observed that the site stopped bleeding 30 seconds after patch placement and good adhesion to surrounding tissue was achieved. About 1 hour after placement, the hind leg was "mobilized" to simulate movement. During and after this movement, the patch remains adhered to the defect and surrounding tissue. Pulses were found on both sides (distal and proximal) of the placed patch.

Procedure 3 femoral artery wrap placement. The blood flow was stopped at the 3-5cm portion of the right femoral artery using a clamp and vascular ring. A small longitudinal defect is created along the artery using a scalpel. The defect was sutured with 2-3 sutures. Bleeding defects were confirmed by removal of the proximal clamp and rated as severe pulsatile bleeding. The clamp is reapplied to stop blood flow and the area is cleared of blood build-up. The dry patch was placed under the defect site with the blue side facing up. The patch was then wetted with saline and wrapped around the defect site to bring the blue side into contact with the target bleeding. Manual pressure was applied to the patch using a pre-moistened gauze sheet for 30 seconds. After manual pressurization for 30 seconds, the gauze was removed. The patch was evaluated for hemostasis and adhesion. Arterial blood flow was confirmed by examining the pulse on both sides of the patch placed. It was observed that the site stopped bleeding 30 seconds after patch placement and good adhesion to surrounding tissue was achieved. About 15 minutes after placement, the hind leg was "mobilized" to simulate movement. During and after this movement, the patch remains adhered to the defect and surrounding tissue. Pulses were found on both sides (distal and proximal) of the placed patch.

Procedure 4, placement on bleeding suture. Heparin was administered to the animals and the procedure was completed with anticoagulation. The right carotid artery was isolated and the graft material was anastomosed in an end-to-end fashion (Gore Acuseal, ECH060020 a). As active blood flows through the artery and graft material, a bleeding area is created by manipulating/removing sutures at the distal anastomosis. Bleeding was assessed as 3 (medium) using Adam scale. Two pieces (2 x 2 cm) of test patch a were placed along the suture patch to cover the defect with the blue side facing the target bleeding. Manual pressurization was performed using a pre-moistened gauze sheet and was maintained for 30 seconds. After 30 seconds of manual pressurization, the gauze was removed and the patch was evaluated for hemostasis and adhesion. After 30 seconds, hemostasis was achieved. The patch adheres to the suture thread, but has little adhesion to the graft material. The suture was observed to close after anticoagulation as well as before anticoagulation.

Procedure 5 placement over graft defect. The procedure was completed using anticoagulation. The procedure was performed at the same site as described in procedure 4, with No. 14 being used for puncturing the graft material. The puncture was evaluated to ensure stable, moderate flow of blood from the defect (Adams score 3). Test patch a was placed on the graft defect. Manual pressure was applied to the patch using a pre-moistened gauze sheet for 30 seconds. After manual pressurization for 30 seconds, the gauze was removed. The patch was evaluated for hemostasis and adhesion. After 30 seconds, the target bleeding was observed to begin to close. The adhesion of the patch to the graft material was observed to be small. The patch can be pulled up from the bleeding site with forceps.

This study showed that placement of test patch a successfully blocked defects common in cardiovascular surgery, including pulsatile femoral artery perforation and end-to-end anastomosis between carotid artery and graft material. All applications of test patch a achieved hemostasis (or occlusion) at or before 30 seconds post-placement. After hindlimb flexion, the patch remains stable and adheres to the tissue at the placement site. The patch successfully controlled bleeding from the graft material. In addition, patch blocking performance remained consistent after heparin administration to animals.

EXAMPLE 6 orthopedics and cardiovascular Defect Studies

This example evaluates the hemostatic effect of hemostatic patches prepared according to example 1 after various placement in acute, non-GLP porcine orthopedic and cardiovascular defect models.

Part a. Test patches. A set of hemostatic patches ("test patch a") prepared according to example 1 using substrate type a was used in this study. All placement was done with the patch dried and pressure applied by the wet gauze. Both 2X 2cm and 2X 4cm patches were used. After placement, the patch was made flexible by applying pressure with pre-moistened gauze.

Part B. Initial preparation of animal defect model. The study used a 27kg acute (york summer) boar. An incision is made in the skin to expose the tibial diaphysis. Blunt dissection was then performed through the underlying subcutaneous tissue and muscle. The muscle is retracted and fascia surrounding the target site is dissected from the bone surface. A dental drill with an approximately 2-3mm ball drill bit was used to create the targeted cortical bleeding defect. The defect is irrigated with saline to remove debris and avoid tissue heating during production.

An incision is then made in the skin to expose the femoral condyle. Blunt dissection was then performed through the underlying subcutaneous tissue and muscle. The muscle is retracted and fascia surrounding the target site is dissected from the bone surface. A dental drill with an approximately 2-3mm ball drill bit was used to create the targeted cortical bleeding defect. The defect is irrigated with saline to remove debris and avoid tissue heating during production.

Finally, groin incisions were made to expose each femoral artery. Blunt dissection was performed through underlying subcutaneous tissue and muscle. The muscle is retracted and fascia surrounding the target vessel is dissected from the vessel surface. The side branch of the vessel was ligated with silk suture material and clips. After proximal and distal control of the artery is obtained using the vascular ring and vascular clamps, the vessel is temporarily occluded.

All bleeding evaluations were performed using Adams scale.

Part C defect creation, patch procedure and results.

Procedure 1. Tibial diaphysis defect. Defects of about 3mm diameter and about 4mm depth were created on the tibial diaphysis using a dental drill and ball drill. Bleeding was confirmed and assessed as very mild (Adams score 1). The patch was cut into approximately 1X 2cm sheets. The patch was placed in a manner to cover the defect with the blue side bleeding toward the target. Manual pressure was applied to the patch using a pre-moistened gauze sheet for 30 seconds. After manual pressurization for 30 seconds, the gauze was removed. The patch was evaluated for hemostasis and adhesion. The site was observed to be occluded 30 seconds after patch placement. There is evidence that bleeding continues under the patch as the site is observed over time, but the site remains closed and the patch remains well adhered.

Procedure 2. Tibial diaphysis larger defect. Operating at the same site described in procedure 1, a large defect of about 6mm in diameter and about 9mm in depth was created on the tibial diaphysis using a dental drill and ball drill. Bleeding was confirmed and assessed as very mild (Adams score 1). A2X 2cm patch was cut into discs matching the size of the defect using a 6mm biopsy punch. Two of these discs were placed into the defect using forceps with the blue side of the first patch bleeding toward the target at the bottom of the defect. Each subsequent patch is stacked on top of the previous patch with the blue side against the previous patch. These patches were placed to address wall bleeding from the resulting defect. Manual pressure was applied to the top patch using a pre-moistened gauze sheet for 30 seconds. After 30 seconds of pressurization, the gauze was removed. Hemostasis and patch adhesion at this site were assessed. Hemostasis was observed to be achieved 30 seconds after patch placement.

Procedure 3 femoral condyle defect. Defects of about 6mm diameter and about 3mm depth were created on the femoral condyle using a dental drill and ball drill. Bleeding was confirmed and assessed as very mild (Adams score 1). The 2 x 2cm test patch a pieces were cut into discs matching the defect size using a 6mm biopsy punch. The disc was placed into the defect using forceps with the blue side of the patch facing the target bleeding. Pressure was applied to the patch with a pre-moistened gauze piece using a plunger from a 1ml syringe for 30 seconds. After 30 seconds of pressurization, the gauze was removed. The site was evaluated for hemostasis and patch adhesion. Hemostasis was observed to be achieved 30 seconds after patch placement.

Procedure 4. Deep defect of femoral condyle. Defects of about 6mm diameter and about 9mm depth were created on the femoral condyle using a dental drill and ball drill. Bleeding was confirmed and assessed as mild (Adams score 2). A2X 2cm test patch A was cut into discs using a 6mm biopsy punch. Four of these discs were placed in a manner that matched within the defect with the blue side of the first patch bleeding toward the target at the bottom of the defect. Each subsequent patch is stacked on top of the previous patch with the blue side against the previous patch. These patches were placed to address wall bleeding from the resulting defect. Pressure was applied to the patch with a pre-moistened gauze piece using a plunger from a 1ml syringe for 30 seconds. After 30 seconds of pressurization, the gauze was removed. The site was evaluated for hemostasis and patch adhesion. Hemostasis was observed to be achieved 30 seconds after patch placement.

Procedure 5 femoral artery suture defect. The clamp and vascular ring were used to stop blood flow in the 3-5cm section of the femoral artery. Two vascular punctures were performed using a 25 gauge needle to simulate the suture of a vascular repair procedure. The arteries were loosened to ensure that bleeding defects had occurred, and bleeding was rated using the Adams scale. Pulsatile bleeding was assessed as severe (Adams score 4). The artery is re-clamped to stop blood flow and the area is cleared of blood build-up. A piece of gauze was cut and moistened with clean saline. A 2 x 4cm patch was placed on top of the wet gauze with the blue side facing away from the gauze. The patch/gauze pair was then slid under the artery with the blue side of the patch bleeding toward the target. The user holds the two ends of the gauze and lifts them toward each other until the two ends of the gauze come into contact. Then, pressure is applied to the patch-patch contact area ("tail") so that the central area of the patch wraps around the blood vessel and the tails of the patch adhere to each other. Care was taken to ensure that the two tail-formed channels were not located directly above the bleeding site. Manual pressure was then applied to the patch through the gauze for 30 seconds. After manual pressurization for 30 seconds, the gauze was removed. Blood flow in the region is then restored by removing the vascular ring and the clamp. Arterial blood flow was confirmed by examining the pulse on both sides of the patch placed. The patches were then evaluated for hemostasis and adhesion. The tail of the patch was trimmed with Mei Zengbao (metanbaum) scissors, leaving about 2-3mm tail along the length of the patch portion of the artery. It was observed that the application site stopped bleeding at 30 seconds, good adhesion to the artery was achieved, and pulses were found on both the distal and proximal sides of the patch.

Procedure 6 contralateral femoral artery defects. The procedure described in procedure 5 was applied to the contralateral femoral artery. The resulting pulsatile bleeding defect was assessed as severe (Adams score 4). Again, it was observed that the application site stopped bleeding at 30 seconds, good adhesion to the artery was achieved, and pulses were found on both the distal and proximal sides of the patch.

Another study evaluated test patch a in chronic sheep carotid arterectomy using a patch closure model. 7 days after implantation in the model, test patch a resulted in stable vascular repair, while angiographic assessment did not find any signs of bleeding.

This study showed that placement of test patch a successfully blocked both condylar and diaphyseal bone defects (with very mild to mild bleeding) as well as bilateral pulsatile femoral artery defects (with severe bleeding). In each case, hemostasis (or occlusion) was achieved 30 seconds or before placement of the dry patch. The syringe plunger was successfully used to apply pressure to patches placed in deeper bone defects. Alternative wrap-around placement methods have been successfully used to treat pulsatile femoral artery perforation.

EXAMPLE 7 Soft organ and orthopedic defect Joint Studies

This example exemplifies the use of soft organ and orthopedic surgical patches in patients.

Part a. Test patches and control products. The study used three classes of hemostatic patches prepared according to example 1 using substrate type a ("test patch a"), substrate type B ("test patch B") and substrate C ("test patch C"), respectively. The control product is water-insoluble pig gelatin sponge with the thickness of 2mmAbsorbable gelatin sponge, johnson and Johnson, product code 1975), to which recombinant thrombin was added (Baxter,) ("Control patch C"). Each sample was tried dry and pre-wet placed.

And B, preparing an animal defect model. In a training laboratory setting, the patches described in section a are provided to the surgeon. An acute (yokexia) pig was cut along the anterior (ventral) midline and the liver was isolated. The animals had the following characteristics of body weight (48.2 kg), sex (M), anticoagulation (ACT: 242). ACT is recorded prior to first placement. Defects were created in the spleen and in both the left and right inner lobes of the liver. Each organ was penetrated using an 8mm biopsy punch initially to a target depth of about 7 mm. Subsequently, a target depth of about 2mm was used. Mei Zengbao (Metzenbaum) scissors were then used to remove the emboli generated by the penetrator. At this time, bleeding was evaluated. According to the spot level SBSS, a target >3 is ideal. If the target bleeding score is not reached, the organ is penetrated again using the biopsy punch until the target score is reached. Bleeding defects are moderate to severe. Prior to placement of the product, the defect site bleeding was treated with clean dry gauze.

Part C. Patch evaluation procedure and results. Clean gauze was moistened with clean sterile saline. The test patch sample was placed against the wet gauze such that the blue surface of the patch was facing away from the gauze. The gauze to treat the bleeding is removed from the defect site. The patch is immediately placed on the defect site such that the blue side of the patch is in contact with the defect and as centered as possible in the defect. With the hands open, a strong and uniform pressure was applied to the back side of the patch with wet gauze and held for 30 seconds. The pressure was then carefully reduced and the gauze carefully removed from the back side surface of the applied patch. If there is any adhesion of the gauze to the patch, a clean surgical instrument is gently applied to the edge of the patch, or gentle rinsing is used to separate the gauze from the patch while minimizing interference. After a 30 second evaluation period, 30 second bleeding scores were recorded according to the spot grade SBSS. Then, the edge of the patch was gently lifted using a pair of tweezers to test adhesion. The procedure was repeated for each patch sample. A modified procedure was used for each patch sample, wherein the patch was placed without pre-wetting with gauze.

And part D. Observing.

Test patch a resulted in hemostasis at each application. Occlusion of the defect is more effective when pressure is applied to the hollow defect and when the patch is pre-wetted (rather than dry applied over the hollow organ defect). Application of the pre-moistened patch resulted in the patch not protruding/bulging and no blood red core formed on the patch over the hollow defect. Test patch B provided similar results to test patch a and resulted in hemostasis at each application. The application of test patches a and B successfully improved the experience of the surgeon with the length of time after patch placement. Multiple test patch C samples were tried, but in each case the patches adhered to gauze during placement. Removal of the gauze causes tearing of the substrate, which results in re-bleeding. Control patch C was successfully used to produce hemostasis in both the liver and spleen. However, the control patch C had poor adhesion to the tissue and there was a high risk of the surgeon falling off the product. Both the test patch and the control patch showed a "dome effect" due to swelling of the blood under the patch/product at the defect site. By applying pressure to the applied patch/product, the dome effect is generally avoided.

The results indicate that test patch a and test patch B provide good adhesion to tissue and rapid hemostasis in a patch that is relatively easy to use. Test patch C failed to achieve sustained hemostasis by the process of use. Too high a porosity of the substrate of test patch C is believed to be associated with excessive blood flow from the defect through the active face and into the substrate, as the hydrogel can migrate through the highly porous substrate. This study shows that the active surface composition used with a suitable substrate contributes to the performance and usability of the patch. Control patch C failed to achieve good adhesion to tissue.

EXAMPLE 8 simulated cervical defect study

This example exemplifies the use of a tapered mandrel to create hemostasis in a simulated cervical defect.

Part a. Test patches. A set of conical hemostatic patches was prepared according to the general procedure of example 1 using base type a. The patch is further formed into a cone shape by a series of manufacturing steps of cutting the patch along one side to near the center of the patch. And then slightly heated and shaped into a generally conical shape. The overlapping cut portions are then secured together to stabilize the shape until the PEG cools.

And B, preparing an animal defect model. An acute (yoktha) pig was opened to isolate the abdominal wall of the pig. Prior to the first placement, the anticoagulated ACT exceeded 300. An 8mm biopsy punch was used to penetrate the abdominal wall to a target depth of approximately 7 mm. Mei Zengbao (Metzenbaum) scissors were then used to remove the emboli generated by the penetrator. At this time, bleeding was evaluated. Bleeding according to a spot grade SBSS of 3 was achieved. Prior to placement of the product, the defect site bleeding was treated with clean dry gauze.

Part C. Patch evaluation procedure and results. The test patch sample was placed over the defect such that the blue surface of the cone-shaped patch was facing the defect. The handle of the mandrel is grasped and the tapered portion of the mandrel with the tapered patch is pressed into the defect. A gentle but constant pressure was applied to the patch through the mandrel for 30 seconds. The pressure was then carefully reduced and the mandrel carefully removed from the convex (back side) surface of the applied patch. Some adhesion of the patch to the mandrel was observed and the mandrel was separated from the patch using a clean surgical instrument while minimizing interference. After a 30 second evaluation period, hemostasis was assessed. In a second application, a modified procedure is used in which a piece of wet gauze is placed between the conical patch and the mandrel prior to pressing the patch into the defect. During removal of the mandrel and gauze from the applied patch, no adhesion of the patch to the mandrel or gauze was observed. After a 30 second evaluation period, hemostasis was assessed.

And part D. Observing.

Both applications were used to achieve good adhesion of the patch to the defect at 30 seconds. While the adhesion of the patch to the mandrel in the first application results in a loss of hemostatic effect upon removal of the mandrel, the improved placement procedure used in the second application results in maintenance of hemostasis after removal of the mandrel. The results indicate that the shaped mandrel can be used to place preformed patches in locations that are not readily accessible for direct manual application ("remote locations"). The results also demonstrate that the preformed patch and correspondingly shaped mandrel can be advantageously used to assist in aligning, placing, and applying the preformed patch to remote sites and non-remote sites. The shaped mandrel allows for more consistent pressure to be applied to the entire surface of the preformed patch that is in contact with the defect. Applying consistent pressure promotes rapid hemostasis by reducing the likelihood of bleeding underneath the patch. Based on the results of the study, it is expected that the tapered patches and corresponding tapered mandrels will be suitable for achieving hemostasis of cervical bleeding defects, as shown in fig. 12A and 12B.

Example 9 preparation of a Flexible hemostatic Patch with compressed base

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

Part a. Substrate compression test.

Two types of substrates were used in this study, as shown in table 13. Both substrates E and F are foamed gelatin/collagen substrates, which are obtained from different commercial suppliers. Commercial foamed gelatin substrates were thermally crosslinked in an oven for several hours according to the time and temperature ranges described above. The substrate sample was about 10cm wide, 20cm long, and 7mm thick.

TABLE 13

Substrate type	Characteristics of	Initial thickness of
			E	Foaming gelatin/collagen	7mm
F	Foaming gelatin/collagen	7mm

Substrates E and F were compressed using calender rolls. For convenience, the compression was performed using a pasta roller, which was set to correspond to a distance (i.e., gap) between the proximal surfaces of the calender rollers of about 5mm. Fig. 15A and 15B are SEM images of the surface of the sample of the substrate E before and after compression, respectively. Fig. 15C and 15D are SEM images of the surface of the sample of the substrate F before and after compression, respectively. Fig. 15A-15D were captured by back scattering using 25 x magnification. The difference between the pore structures of substrate E and substrate F prior to compression can be seen visually in fig. 15A and 15C. Although fig. 15A and 15C both show a range of pore sizes, in general, the macropores in fig. 15A are larger than the macropores in fig. 15C. In addition, the material scaffold around the large pores in matrix E (fig. 15A) is significantly thinner than the material scaffold around the pores in matrix F (fig. 15C). Referring to fig. 15B, after compression, the pore structure of substrate E appears to collapse and fracture and generally lacks the thin scaffold material shown in fig. 15A. Referring to fig. 15D, after compression, the pore structure of substrate F appears to be a similar but denser version of the structure of the uncompressed sample (fig. 15C). Table 14 shows the average pore area fraction and average pore size of the SEM images of figures 15A-15D as determined using ImageJ image analysis software. The measurement of the average pore area fraction is semi-quantitative in that both the pores of the image surface and some of the pores below the image surface are captured. The data in table 14 shows that the average pore area fractions of the uncompressed and compressed samples are similar. The results show that there is a significant difference in foam/scaffold structure between substrate E and substrate F.

TABLE 14

Fluid absorption, flexural strength, shear force, compressive force and conformality before and after compression were further evaluated for a set of substrate E samples. For each measurement, the results of ten replicates were recorded as shown in table 15. Fluid absorption was tested by weighing each of the ten uncompressed samples at the time of drying (initial dry weight) and after 15 seconds of soaking in saline (final weight). The fluid absorption of each sample was calculated as (final weight-initial dry weight)/100% of the initial dry weight. The average fluid absorption of uncompressed substrate E was recorded as the average of the fluid absorption of 10 uncompressed samples. Ten dry, uncompressed samples of substrate E were each subjected to a 3-point bending test by using a texture analyzer machine (model TA-XT Plus C) equipped with a 3-point bending device, and flexural strength was measured according to ASTM D790-17 (incorporated herein by reference). Each test specimen was approximately 2.5cm wide and 6.5cm long. The maximum shear force is measured by loading the dry uncompressed test sample as a cantilever and applying a force. The maximum shear force is recorded as the force at break. Each test specimen was approximately 2.5cm wide by 6.5cm long, with 1cm held by the test grip. Column strength (or maximum compressive force) was measured by uniaxially compressing ten dry uncompressed samples of substrate E, respectively, using a texture analyzer machine (model TA-XT Plus C). Each test specimen was a dog bone test specimen 2.5cm wide and 7.5cm long. Column strength was recorded as the force at break. Conformality was tested by wrapping the dried sample around a 1/2 inch mandrel. Failure of the samples to crack or break during the test indicated positive conformality and the results were recorded as the number ratio of positive samples per 10 test samples. The average thickness of each sample was measured with a caliper.

The above test was repeated using a set of 10 compressed base samples for each test. The results are shown in table 15. Comparison of the average measurement of the uncompressed substrate sample with the average measurement of the compressed substrate sample showed substantially no change in fluid absorption (360% versus 356%), but the mechanical properties of the sample showed a change. The average flexural, shear and column strength of the compressed samples were lower, but all compressed samples (10/10) were compliant to a 1/2 inch diameter mandrel. Only 3 of the 10 uncompressed samples were compliant to the same 1/2 inch mandrel test. The results indicate that compression of the substrate imparts flexibility/conformability to the substrate without altering fluid absorption. Furthermore, the results show that the compressed samples retain a greater percentage of the original compression and tensile strength than the shear strength (maximum shear), as shown by the column strength and flexural strength measurements. The shear strength of the compressed sample was about 10% of the shear strength of the uncompressed sample. The results indicate that compression of the substrate E using calendering results in significant shear-induced cracking, but is still gentle enough to allow the substrate to remain relatively stiff. The results indicate that compression (especially by calendaring) can impart flexibility to the crosslinked gelatin substrate through collapse of the pore structure without producing a measurable loss of fluid absorption and without producing a significant loss of stiffness. The results also show that the thickness variability of the compressed substrate samples is lower than the thickness variability of the uncompressed substrate samples.

TABLE 15

Additional fluid absorption data over time was collected for the uncompressed samples and the compressed samples. Figure 19 shows the average fluid absorption of substrate samples immersed for 15 seconds, 1 minute, 5 minutes or 10 minutes. At 20 hours (not shown in the figure), the average fluid absorption of the uncompressed and compressed base samples was about 1200%. The results indicate that the substrate initially absorbs fluid rapidly, with the absorption tending to smooth at about 10 minutes. The average percent fluid absorption of an uncompressed substrate and a compressed substrate at a given measurement time is typically within the measurement error.

Part B, coated substrate processing and testing.

The coated substrates were prepared by coating a dried blend of the two hydrogel precursors in solution onto a set of compressed samples of substrate E. The substrate samples were prepared for coating by drying in an oven at a temperature of 35 ℃ under ambient air for 18 hours or until the relative humidity of the oven was less than 5%. The thickness of each substrate sample after drying was approximately the same as the thickness before drying. For each coated substrate sample, the first hydrogel precursor was an eight-arm polyethylene glycol-based precursor having a molecular weight of 15,000da and Succinimidyl Glutarate (SG) functional end groups (8A15k PEG SG,Jenkemusa). The second hydrogel precursor is an eight-arm polyethylene glycol-based precursor having a molecular weight of 20,000da and an HCl salt amine functional end group (8 a20k PEG amine-HCl, jenkemusa). The first and second precursors were measured as powders and then melt blended with traces of FD & C Blue #1 in a heated roller system at a temperature above 45 ℃ in a glove box. The molten precursor blend was delivered to a liquid distribution system (FOM Coater, FOM Technologies). A monolayer coating of the melt blend was applied to each substrate sample under inert gas conditions. The precursor was applied through a heated slot die head located at a gap of 4.5mm above the bottom surface of a substrate of approximately 5mm thickness. Through this process, coating of the substrate involves injecting the melt blend into the substrate as the slot die head compresses the substrate. The precursor impregnated areas of each substrate ("precursor/substrate network areas") have an average thickness of about 0.25mm, typically to extend at least about 0.05mm above the substrate surface. The mixed precursor coated substrate is cured at room temperature under inert gas conditions. The thickness of each of the resulting coated substrates was measured to be about 5.25mm.

One of the coated substrates (sample 1) was left as an "uncompressed sample", while the remaining coated substrate samples (samples 2-4) were compressed after coating using calender rolls. Fig. 16A-D show SEM images of representative portions of the surfaces of samples 1-4, respectively. For the uncompressed sample (sample 1), fig. 16A shows that the coated sample has relatively non-uniform cracks on the surface, which include some relatively larger cracks compared to the compressed cracks of fig. 16B-D. (note that the magnification of fig. 16A is lower than fig. 16B-d.) the large crack seen in fig. 16A is a result of sample handling/transport and indicates that the post-coating cured precursor is rigid and brittle if strain relief is not provided. Although the cured precursor in fig. 16A (sample 1) had brittleness, it was observed that the precursor adhered well to the substrate. For samples 2-4, post-coating compression was performed using a pasta roll, which was set to correspond to the distance between the near surfaces of the calender rolls (i.e., gap). One coated sample (sample 2, fig. 16B) was compressed at a setting corresponding to a gap of about 5 mm. The other coated sample (sample 3, fig. 16C) was compressed at a setting corresponding to a gap of about 2 mm. The other coated sample (sample 4, fig. 16D) was compressed in two steps by first compressing at a gap of about 5mm and then compressing at a gap of about 2 mm. Fig. 16B-D show that compression of the coated substrate introduces surface cracking, with direct compression using a 2mm gap (sample 3, fig. 16C) introducing significant surface cracking. SEM image of sample 4 (fig. 16D) shows that two-step compression can provide a more consistent fracture by using a first compression step to release some of the strain and a second compression step to introduce additional fracture. SEM images of samples 2-4 (fig. 16B-D) qualitatively demonstrate that compressed samples 2-4 are less brittle than uncompressed sample 1 (fig. 16A) because there are no non-uniform/wide cracks as shown in fig. 16A. All samples showed good adhesion of the precursor to the substrate, including during handling/transportation.

Fig. 17A and 17B show SEM images of cross sections of representative portions of sample 1 and sample 2. Uncompressed sample 1 (fig. 17A) and compressed sample 2 (fig. 17B) have similar underlying substrates as the uncompressed and compressed substrates described in section a. In particular, the lower substrate of sample 1 (fig. 17A) shows relatively large pores surrounded by a thin gelatin scaffold. The underlying substrate of sample 2 (fig. 17B) shows a collapsed/ruptured pore structure. The precursor/substrate network region ("network") of sample 1 was measured to be about 200-230 microns thick. The precursor/substrate network region of sample 2 measured about 170-320 microns thick. The wider range of network thicknesses for the compressed samples appears to be related to compression, which results in more cracking of the precursor and more integration into the substrate, and thus a wider overall range of network cross-sectional footprints. Fig. 17A and 17B also illustrate that the precursor permeates relatively uniformly and across the substrate surface. The precursor does not penetrate completely through the substrate.

In addition to the above-described tests, the effect of the coating on the compressed substrate was also investigated relative to the uncompressed substrate. Fig. 18A and 18B show a coated substrate prepared as described above, except that a coating was applied to the uncompressed substrate E. The white areas in fig. 18A and 18B are areas where the precursor coating is not sufficiently covered. In contrast, fig. 18C shows a coated substrate in which a coating is applied to a compressed substrate E. There are no white areas and the blue coating is evenly distributed even along the edge to the exclusion boundary of the edge. (note that the images in fig. 18A-C were taken through the glass of the glove box, and thus there was some reflection in the images.)

The results of the study in this section showed that the compression coated patch showed more cracks in the PEG-based network than the uncompressed patch. Compression coated patches also show more penetration of the precursor into the substrate layer, indicating that delamination will be reduced (i.e., the adhesion of the precursor to the substrate will be improved). In addition, the results of this study demonstrate that pre-coat compression can be used to remove depressions and other inconsistencies in the substrate prior to coating, which can visually improve coating consistency.

And C, testing the patch.

Four coated substrate samples were prepared using the method described in section B. Two of the samples (patch samples 1 and 2) were not compressed. Two of the samples (patch samples 3 and 4) were compressed using calender rolls with a gap of 5 mm. The precursor adhered well to the substrate for all patch samples. There is no evidence that the precursor flaked off the substrate during processing.

After these preliminary observations, each patch sample was cut into 8mm disk test specimens using an 8mm biopsy punch and burst pressure was tested. Table 16 shows burst pressure results. Patch samples 1 and 2 (uncompressed) and patch samples 3 and 4 (compressed) had similar average burst pressure results, but the standard deviation of the burst pressure results for the compressed samples was lower. The results indicate that compression can improve the consistency of patch performance. The improved uniformity may be due to more collapse of the pore structure of the substrate, reduced variability in substrate thickness, improved uniformity of precursor/substrate network, increased flexibility/conformability of the hemostatic patch, and/or improved adhesion of the precursor to the substrate.

Table 16

The results of this study show that compression of the crosslinked gelatin substrate during coating with the precursor melt blend produces a consistent and cohesive precursor/substrate network at the top surface of the substrate. The precursor adheres to the substrate and does not flake off the substrate during handling/transport. The results of this study further demonstrate that compression can be used to increase flexibility/conformability and improve the uniformity of performance of hemostatic patches without producing a measurable change in fluid absorbency or burst pressure. The results demonstrate that compression hemostatic patches alleviate some of the variability associated with applying patches to a target surface by manual compression, which aids in better adhesion to the target surface and higher burst strength. The results also show that the shear forces introduced by the calendering application of compression can help improve flexibility and performance. The results also indicate that a two or more stage compression process would be advantageous. In particular, the results indicate that an initial compression of the bare substrate is performed to initiate hole cracking/collapsing, followed by a second compression after coating to further crack/collapse the holes of the substrate and also crack the coating.

The above embodiments are intended to be illustrative and not limiting. Additional embodiments are within the scope of the following claims. In addition, although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Any incorporation by reference of documents above is limited such that no subject matter is included that is contrary to the explicit disclosure herein. Insofar as specific structures, compositions, and/or processes are described herein as having components, elements, ingredients, or other partitions, it is to be understood that the disclosure herein encompasses specific embodiments, including specific components, elements, ingredients, other partitions, or combinations thereof, as well as embodiments consisting essentially of such specific components, ingredients, or other partitions, or combinations thereof, which may include additional features that do not alter the basic nature of the subject matter, as suggested in the discussion, unless otherwise specifically indicated. The term "about" as used herein refers to the expected uncertainty of the relevant value as understood by one of ordinary skill in the art in a particular context. For any set of ranges presented herein for any parameter, these should be construed as also specifically describing the relevant ranges wherein the lower limit of one range is combined with the upper limit of another specific range.

Claims

1. A medical patch comprising a biocompatible substrate and a dried hydrogel precursor layer on the substrate, the dried hydrogel precursor layer comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of protonated amine groups and no more than about 2 wt % of water, and wherein both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked and are blended or in direct contact with each other.

2 . The medical patch of claim 1 , wherein the dried hydrogel precursor layer comprises a blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor.

3. The medical patch according to claim 1 or claim 2, wherein the substrate persists in an in vitro physiological solution maintained at 37°C for less than 30 days.

4. The medical patch according to claim 1 or claim 2, wherein the substrate persists in an in vitro physiological solution maintained at 37°C for less than 2 weeks.

5. The medical patch according to any one of claims 1 to 4, wherein the substrate is capable of absorbing 300 wt% to 3000 wt% of water.

6. The medical patch according to any one of claims 1 to 5, wherein the substrate comprises gelatin.

7. The medical patch of claim 6, wherein the substrate is partially thermally cross-linked, and wherein the substrate is a foam, a nonwoven tufted material, or a nonwoven felt material.

8. The medical patch of any one of claims 1-7, wherein the dried hydrogel precursor layer comprises multiple layers of a blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor.

9. The medical patch of claim 8, wherein the dried hydrogel precursor layer is formed from a neat melt blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor.

10. The medical patch according to any one of claims 1 to 7, wherein the dried hydrogel precursor layer comprises a stack of one or more sublayers of the electrophilic hydrogel precursor and one or more sublayers of the nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with each other.

11. The medical patch of any one of claims 1-7, wherein the substrate consists essentially of gelatin and the dried hydrogel precursor layer consists of a single solid layer consisting essentially of the electrophilic hydrogel precursor, the nucleophilic hydrogel precursor, and an optional imaging agent, wherein the imaging agent is biocompatible.

12. The medical patch of any one of claims 1-11, wherein the electrophilic hydrogel precursor has a first hydrophilic core comprising a polymer having a molecular weight of at least about 5000 Da, and wherein the nucleophilic hydrogel precursor has a second hydrophilic core comprising a polymer having a molecular weight of at least about 2500 Da.

13. The medical patch of 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.

14. The medical patch according to claim 12, wherein the first hydrophilic core and/or the second hydrophilic core comprises polyethylene glycol, polyvinyl alcohol, polyoxazoline, copolymers thereof or mixtures thereof or other water-soluble medical polymers having functional groups that can be modified, wherein the first hydrophilic core and the second hydrophilic core comprise the same polymer.

15. The medical patch according to any one of claims 1-14, wherein the plurality of arms for the electrophilic hydrogel precursor and the plurality of arms for the nucleophilic hydrogel precursor are independently 3 to 8, and wherein the first hydrophilic core and the second hydrophilic core comprise polyethylene glycol.

16. The medical patch according to any one of claims 1 to 15, wherein the electrophilic hydrogel precursor has an electrophilic functional group comprising an ester.

17. The medical patch of claim 16, wherein the ester is a succinimidyl ester.

18. The medical patch of any one of claims 1-17, wherein the ratio of electrophilic functional groups to protonated amine groups is no more than about 1.

19. The medical patch of any one of claims 1-18, wherein the ratio of electrophilic functional groups to protonated amine groups is about 1.

20. The medical patch of any one of claims 1-18, wherein the ratio of electrophilic functional groups to protonated amine groups is from about 0.95 to about 1.05.

21. The medical patch of any one of claims 1-20, wherein the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are each water soluble.

22. The medical patch of any one of claims 1-21, wherein the medical patch further comprises a therapeutic agent.

23. The medical patch of claim 22, wherein the therapeutic agent comprises an analgesic, an anesthetic, a steroid, an antibiotic, a steroid, an anti-infective agent, an anti-inflammatory agent, a nonsteroidal anti-inflammatory drug, an anti-proliferative agent, or a combination thereof.

24. The medical patch of any one of claims 1-23, wherein the dried hydrogel precursor layer further comprises an imaging agent.

25. The medical patch of claim 24, wherein the imaging agent is biocompatible and comprises a colorant, a fluorescent molecule, a contrast agent, or a combination thereof.

26. The medical patch of claim 24 or claim 25, wherein the medical patch has a first side comprising the substrate and a second side comprising the dried hydrogel precursor layer and the imaging agent, wherein the first side is substantially free of the imaging agent.

27. The medical patch of any one of claims 1-26, wherein the medical patch is flexible and conformable when dry.

28. The medical patch of claim 27, wherein the patch can be rolled up for laparoscopic delivery through a trocar.

29. The medical patch of any one of claims 1-28, 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.

30. The medical patch of any one of claims 1-29, wherein the medical patch is free of blood components and human body components.

31. The medical patch of any one of claims 1-30, wherein contact with a relevant physiological fluid causes the dried hydrogel precursor layer to form a hydrogel.

32. The medical patch of any one of claims 1-31, wherein the substrate does not adhere to surgical gloves or gauze moistened with a non-buffered solution when dry or wet.

33. The medical patch of any one of claims 1-32, wherein the medical patch has a storage stability against significant gelling under refrigerated conditions for at least about 1 year.

34. The medical patch of any one of claims 1-33, wherein contact with physiological fluids results in complete absorption of the medical patch in no more than about 28 days.

35. The medical patch of any one of claims 1-33, wherein contact with physiological fluids results in complete absorption of the medical patch in no more than about 9 days.

36. The medical patch of any one of claims 1-35, wherein the medical patch has a three-dimensional contoured shape.

37. The medical patch of claim 36, wherein the three-dimensional shape is a perfect cone or a truncated cone.

38. A wound packing composition comprising an amount of minced material from a patch according to any one of claims 1 to 37.

39. A medical patch comprising a biocompatible substrate and a dried hydrogel precursor layer on the substrate, the dried hydrogel precursor layer comprising a PEG-electrophilic hydrogel precursor and a PEG-nucleophilic hydrogel precursor and no more than about 2 weight percent water, the PEG-electrophilic hydrogel precursor having a plurality of arms having terminal reactive electrophilic groups, the PEG-nucleophilic hydrogel precursor having a plurality of arms having terminal protonated amine groups, and wherein both the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor are substantially uncross-linked, wherein the dried hydrogel precursor layer forms a cross-linked hydrogel within no more than 5 minutes after hydration with a physiological solution.

40. The medical patch of claim 39, wherein the substrate is biodegradable and comprises gelatin and is partially thermally cross-linked, wherein the substrate is a foam, a nonwoven tufted material or a nonwoven felt material and persists for less than 2 weeks in an in vitro physiological solution maintained at 37°C.

41. The medical patch of claim 39 or claim 40, wherein the dried hydrogel precursor layer comprises multiple layers of a blend of the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor, or a stack of one or more sublayers of the PEG-electrophilic hydrogel precursor and one or more sublayers of the PEG-nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with each other, and wherein the width and length of the medical patch are independently about 1 cm to about 15 cm and the thickness is about 0.5 mm to about 5 mm.

42. The medical patch of any one of claims 39-41, 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 group comprises an ester.

43. A wound packing composition comprising a quantity of minced material from a patch according to any one of claims 39 to 42.

44. A method for forming a medical patch, the method comprising:

One or more layers of liquid are applied 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 blend of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, or a stack of sublayers of each of the electrophilic hydrogel precursor and the protected nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with each other, wherein the protected nucleophilic hydrogel precursor comprises an acidified amine, wherein the liquid comprises the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor, and wherein the liquid comprises a melt or non-aqueous solution of the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor.

45. The method of claim 44, wherein the temperature of the liquid does not exceed about 95°C.

46. A method according to claim 44 or claim 45, further comprising drying the porous hydrophilic substrate prior to applying.

47. The method of claim 46, wherein the drying is performed until the porous hydrophilic substrate has a water content of no more than about 2% by weight water.

48. The method of any one of claims 44-47, wherein the applying comprises slot die coating, doctor blade, spraying or sprinkling.

49. The method of any one of claims 44-48, wherein the medical patch has a thickness of no more than about 5 mm.

50. The method of any one of claims 44-49, further comprising sterilizing the medical patch by radiation.

51. The method of any one of claims 44-50, further comprising forming the medical patch into a three-dimensional contoured shape after applying the one or more layers of the liquid.

52. A method for using a medical patch, the method comprising:

One or more medical patches are placed on or in 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 blend or in the form of multiple stacked sublayers in direct contact with each other.

53. The method of claim 52, wherein the one or more medical patches are provided in a disposable pharmaceutical package having a high moisture barrier and/or a desiccant.

54. The method of claim 52 or claim 53, further comprising contouring the one or more medical patches to have a three-dimensional shape corresponding to the interior of the bleeding defect.

55. The method of any one of claims 52-54, wherein the organ is a bone, a gland, a digestive organ, a lung organ, a urinary organ, a reproductive organ, a blood vessel, an interface with a natural or synthetic implant, or a combination thereof.

56. The method of any one of claims 52-55, wherein the bleeding defect is a suture, a puncture wound, a gunshot wound, a cavity, an abrasion, a biopsy puncture hole, a graft interface, or a combination thereof.

57. The method of any one of claims 52-56, wherein the placing is performed without pre-wetting the one or more medical patches.

58. The method of any one of claims 52-57, further comprising wetting the one or more medical patches with non-buffered water or non-buffered saline prior to and/or after placement.

59. The method of any one of claims 52-58, wherein the placing comprises placing the one or more medical patches on the bleeding defect in a non-planar geometry.

60. The method of any one of claims 52-59, wherein the placing comprises wrapping one or more medical patches around the organ.

61. The method of claim 60, wherein the organ is an artery or a vein, and wherein the organ is native, transplanted, or a combination thereof.

62. The method of any one of claims 52-59, wherein the placing comprises directing the medical patch onto or into a bleeding defect with a tubular applicator, wherein the medical patch has a three-dimensional contoured shape.

63. The method of claim 62, wherein the tubular applicator has a shape that integrates with the three-dimensional shape of the medical patch.

64. The method of claim 62, wherein the tubular applicator has a tapered end and the three-dimensional shape of the medical patch is a cone, wherein placing comprises directing the medical patch transvaginally to the cervix using the tubular applicator.

65. The method of any one of claims 52-64, wherein the placing comprises placing one or more first medical patches on the bleeding defect and then placing one or more second medical patches, the one or more second medical patches overlapping at least a portion of the one or more first medical patches.

66. The method of any one of claims 52-65, wherein the placing further comprises applying manual pressure to the one or more medical patches for no longer than about 2 minutes.

67. The method of any one of claims 52-66, wherein the placing results in hemostasis within about 5 minutes.

68. The method of claim 67, wherein the bleeding defect has an Adam score of 1 to 4.

69. The method of any one of claims 52-68, wherein contact with a physiological fluid associated with the organ causes the layer to form a hydrogel in no more than about 2 minutes, wherein the hydrogel adheres to the organ.

70. The method of any one of claims 52-69, wherein the width and length of the one or more medical patches are independently about 1 cm to about 15 cm, wherein the edges of the one or more medical patches adhere to the organ within about 5 minutes of placement.

71. The method of any one of claims 52-70, wherein the bleeding defect comprises blood that has been anticoagulated.

72. The method of any one of claims 52-71, wherein the one or more medical patches are fully absorbed in no more than about 28 days.

73. The method of any one of claims 52-72, wherein the one or more medical patches remain at least partially adhered to the organ until the one or more medical patches are substantially completely absorbed.

74. The method of any one of claims 52-73, wherein the one or more medical patches have a gel time of no more than about 5 minutes at 37°C, wherein the gel time is measured in vitro using a texture analyzer immediately after activation of the patch with a buffer solution having a pH of 8 to generate a force versus time curve, wherein the gel time is the time corresponding to the lowest force on the curve.

75. The method of any one of claims 52-74, wherein the one or more patches have a burst pressure of at least about 50 mm Hg.

76. A particulate composition comprising a blend of a porous hydrophilic material and a hydrogel precursor, wherein the hydrogel precursor comprises an electrophilic hydrogel precursor having multiple electrophilic functional groups and a nucleophilic hydrogel precursor having multiple protonated amine groups and no more than about 2 weight percent of water, wherein both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncross-linked and are in the same particle, or in different particles, or a combination thereof.

77. A particle composition according to claim 76, wherein the porous hydrophilic material and the hydrogel precursor form a composite material within the particle.

78. The particle composition of claim 76, wherein the porous hydrophilic material forms an intra-particle composite with the electrophilic hydrogel precursor or the nucleophilic hydrogel precursor.

79. The particle composition of claim 76, wherein the composite material of the porous hydrophilic material and the hydrogel precursor are in different particles.

80. The particle composition of claim 76, wherein the porous hydrophilic material, the electrophilic hydrogel precursor, and the nucleophilic hydrogel precursor are in different particles.

81. The particle composition of claim 76, wherein the porous hydrophilic material, the electrophilic hydrogel precursor, the nucleophilic hydrogel precursor, or a blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor at least partially coats the porous hydrophilic material.

82. The particle composition of any one of claims 76-81, comprising 10% to 75% by weight of the porous hydrophilic material, wherein the ratio of electrophilic functional groups to protonated amine groups is approximately 1.

83. A particle composition according to any one of claims 76-82, wherein the porous hydrophilic material comprises two or more materials.

84. The granular composition of any one of claims 76-83, comprising particles having an average diameter of about 0.001 mm to about 2 mm.

85. The granular composition of any one of claims 76-84, comprising a powder.

86. The particulate composition of any one of claims 76-85, further comprising an imaging agent and/or a therapeutic agent.

87. A method of using the granular composition according to any one of claims 76-86, the method comprising:

The particulate composition is placed on or in a bleeding defect.

88. A medical patch comprising a biocompatible substrate and a hydrogel precursor presenting 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, wherein the hydrogel precursor at least partially extends into the surface of the biocompatible substrate to form an adhesive hydrogel precursor structure, wherein the adhesive hydrogel precursor structure comprises a blended layer and/or separate adjacent layers of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor, and wherein the medical patch presents a fractured surface of the adhesive hydrogel precursor structure adhered to the biocompatible substrate.

89. The medical patch of claim 88, wherein the biocompatible substrate comprises a foamed gelatin material.

90. The medical patch of claim 89, wherein the foamed gelatin material comprises gelatin felt.

91. The medical patch of claim 88, wherein the biocompatible substrate consists essentially of foamed gelatin having a ruptured cell structure.

92. The medical patch of any one of claims 88-91, wherein the biocompatible substrate is capable of absorbing 100% to 2500% by weight of water relative to the weight of the dry patch.

93. The medical patch of any one of claims 88-92, wherein the biocompatible substrate does not adhere to surgical gloves or gauze moistened with a non-buffered solution when dry or wet.

94. The medical patch of any one of claims 88-93, wherein both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked.

95. The medical patch of any one of claims 88-94, wherein the adhesive hydrogel precursor structure comprises the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor in a plurality of stacked layers in direct contact with each other.

96. The medical patch of any one of claims 88-94, wherein the adhesive hydrogel precursor structure comprises the blended layer.

97. The medical patch of any one of claims 88-96, wherein the adhesive hydrogel precursor structure is free of buffer and free of non-aqueous solvent.

98. The medical patch of any one of claims 88-97, 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.

99. The medical patch of any one of claims 88-98, wherein the adhesive hydrogel precursor structure has a surface that substantially conforms to a surface of the biocompatible substrate.

100. The medical patch of any one of claims 88-99, wherein the medical patch is sufficiently flexible when dry that it can be wrapped around a ^1/2 _inch mandrel without breaking.

101. The medical patch of any one of claims 88-100, wherein the medical patch has an accordion-like folded shape.

102. The medical patch of any one of claims 88-101, wherein the medical patch can be rolled or folded without breaking for laparoscopic delivery through a trocar.

103. The medical patch of any one of claims 88-102, wherein the adhesive hydrogel precursor structure cross-links in less than about 30 seconds to form an adhesive hydrogel structure after exposure to physiological fluid or physiological buffered saline.

104. The medical patch of any one of claims 88-103, wherein the adhesive hydrogel precursor structure spontaneously cross-links to form an adhesive hydrogel structure when exposed to physiological fluids or physiological buffered saline.

105. The medical patch of any one of claims 88-104, wherein the fractured surface comprises a plurality of microcracks and/or fissures resulting from a compression manufacturing step.

106. The medical patch of any one of claims 88-105, wherein the nucleophilic hydrogel precursor comprises a plurality of protonated amine groups.

107. The medical patch of any one of claims 88-106, wherein the electrophilic hydrogel precursor has a first hydrophilic core comprising a polymer having a molecular weight of at least about 5000 Da, and wherein the nucleophilic hydrogel precursor has a second hydrophilic core comprising a polymer having a molecular weight of at least about 2500 Da, wherein the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are each water soluble.

108. The medical patch of 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 copolymers thereof.

109. The medical patch of any one of claims 88-108, wherein the electrophilic hydrogel precursor has an electrophilic functional group comprising a succinimidyl ester.

110. The medical patch of any one of claims 88-109, wherein the medical patch further comprises a therapeutic agent.

111. The medical patch of any one of claims 88-109, wherein the therapeutic agent comprises an analgesic, an anesthetic, a steroid, an antibiotic, a steroid, an anti-infective agent, an anti-inflammatory agent, a nonsteroidal anti-inflammatory drug, an anti-proliferative agent, or a combination thereof.

112. The medical patch of any one of claims 88-111, wherein the adhesive hydrogel precursor structure further comprises an imaging agent.

113. The medical patch of claim 112, wherein the imaging agent is biocompatible and comprises a colorant, a contrast agent, or a combination thereof.

114. The medical patch of any one of claims 88-113, wherein the medical patch has a storage stability against significant gelling for at least about 2 months under dry storage.

115. The medical patch of any one of claims 88-114, wherein the medical patch has a storage stability against significant gelling under refrigerated conditions for at least about 1 year.

116. The medical patch of any one of claims 88-115, wherein the medical patch is provided in a moisture-proof packaging.

117. The medical patch of any one of claims 88-116, wherein contact with physiological fluids results in complete absorption of the medical patch in no more than about 9 days.

118. The medical patch of any one of claims 88-117, wherein the medical patch has a burst pressure of at least about 150 mm Hg.

119. A method for using a flexible medical patch, the method comprising:

One or more flexible medical patches are placed on or in a target bleeding site, wherein the flexible medical patch comprises a biocompatible substrate and a hydrogel precursor presenting 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 blend and/or in a plurality of stacked regions in direct contact with each other, wherein the biocompatible substrate has a ruptured pore structure, wherein the hydrogel precursor is initially dried and substantially uncrosslinked and extends at least partially into the ruptured pore structure of the biocompatible substrate to form an adhesive hydrogel precursor structure, wherein the medical patch is hemostatically adhered to the target bleeding site.

120. The method of claim 119, wherein the biocompatible substrate comprises thermally cross-linked gelatin.

121. The method of claim 119 or claim 120, wherein the placing is performed without pre-wetting the one or more flexible medical patches.

122. The method of any one of claims 119-121, wherein the placing comprises placing the one or more flexible medical patches on the target bleeding site in a non-planar geometry.

123. The method of any one of claims 119-122, wherein the placing comprises wrapping one or more flexible medical patches around a body structure, wherein the body structure comprises the target bleeding site.

124. The method of any one of claims 119-123, wherein the target bleeding site is associated with an artery and/or a vein, and wherein the artery and/or the vein is natural, transplanted, or a combination thereof.

125. The method of any one of claims 119-124, wherein the method further comprises bending or folding the one or more flexible medical patches into a three-dimensional shape prior to placement.

126. The method of claim 125, wherein the three-dimensional shape comprises accordion folds.

127. The method of claim 125, wherein the bending or folding is performed without pre-wetting the one or more flexible medical patches.

128. The method of any one of claims 119-127, wherein placing comprises directing the one or more flexible medical patches through a tubular applicator onto or into the target bleeding site.

129. The method of claim 128, wherein the tubular applicator comprises a cannula.

130. The method of claim 128 or claim 129, wherein the target bleeding site is associated with a laparoscopic surgical site.

131. The method of any one of claims 119-130, wherein the placing further comprises applying manual pressure to the one or more flexible medical patches for no longer than about 30 seconds.

132. The method of any one of claims 119-131, wherein the placing results in hemostasis within about 3 minutes.

133. The method according to any one of claims 119-132, wherein the target bleeding site has an Adam score of 1 to 4 and/or a SPOT score of 1 to 4. Rating is 1 to 5.

134. The method of any one of claims 119-133, wherein contact with a physiological fluid associated with the target bleeding site causes the adhesive hydrogel precursor structure to form an adhesive hydrogel structure in no more than about 30 seconds, wherein the adhesive hydrogel structure adheres to the target bleeding site.

135. The method of any one of claims 119-134, wherein the target bleeding site exudes blood that has been anticoagulated.

136. The method of any one of claims 119-135, wherein the one or more flexible medical patches are completely absorbed in no more than about 28 days.

137. The method of any one of claims 119-136, wherein the one or more flexible medical patches are completely absorbed in less than about 7 days.

138. The method of any one of claims 119-137, 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 substantially completely absorbed.

139. A medical patch comprising a biocompatible substrate and a hydrogel precursor, wherein the hydrogel precursor comprises a solid blend and/or a separate solid layer 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 uncross-linked, wherein the biocompatible substrate comprises thermally cross-linked gelatin having a ruptured pore structure, wherein the hydrogel precursor at least partially extends into the ruptured pore structure of the biocompatible substrate to form an adhesive hydrogel precursor structure.

140. The medical patch of claim 139, wherein the biocompatible substrate comprises a foamed gelatin material, a nonwoven felt gelatin material, or a nonwoven tufted gelatin material.

141. The medical patch of claim 139 or claim 140, wherein the biocompatible substrate comprises a gelatin sponge or gelatin felt capable of absorbing 100% to 2500% by weight of water relative to the dry weight of the patch.

142. The medical patch of claim 139, wherein the biocompatible substrate consists essentially of foamed gelatin and the hydrogel precursor.

143. The medical patch of any one of claims 139-142, wherein the biocompatible substrate has a thickness of about 0.2 mm to about 8 mm when the medical patch is dry.

144. The medical patch of any one of claims 139-143, wherein the medical patch further comprises a therapeutic agent.

145. The medical patch of claim 144, wherein the therapeutic agent comprises an analgesic, an anesthetic, a steroid, an antibiotic, a steroid, an anti-infective agent, an anti-inflammatory drug, a nonsteroidal anti-inflammatory drug, an anti-proliferative agent, or a combination thereof.

146. The medical patch of any one of claims 139-145, wherein the medical patch further comprises an imaging agent.

147. The medical patch of any one of claims 139-146, wherein the adhesive hydrogel precursor structure has a surface that substantially conforms to a surface of the biocompatible substrate.

148. The medical patch of any one of claims 139-147, wherein the hydrogel precursor presents a surface on one side of the biocompatible substrate and is absent on the other side of the biocompatible substrate.

149. The medical patch of any one of claims 139-148, wherein the medical patch is sufficiently flexible when dry that it can be wrapped around a 1/2 inch mandrel without breaking.

150. The medical patch of any one of claims 139-149, wherein the medical patch has a three-dimensional folded shape.

151. The medical patch of any one of claims 139-150, wherein the medical patch has an accordion-like folded shape.

152. The medical patch of any one of claims 139-151, wherein the medical patch can be rolled or folded without breaking for laparoscopic delivery through a trocar.

153. The medical patch of any one of claims 139-152, wherein the adhesive hydrogel precursor structure cross-links in less than about 30 seconds after exposure to physiological fluids or physiological buffered saline.

154. The medical patch of any one of claims 139-153, wherein the adhesive hydrogel precursor structure spontaneously cross-links when exposed to physiological fluids or physiological buffered saline.

155. The medical patch of any one of claims 139-154, wherein the medical patch, when dry, exhibits a fractured surface of the adhesive hydrogel precursor structure adhered to the biocompatible substrate, wherein the fractured surface comprises a plurality of microcracks and/or cracks.

156. The medical patch of any one of claims 139-155, wherein the nucleophilic hydrogel precursor comprises a plurality of protonated amine groups.

157. A medical patch according to any one of claims 139-156, 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 having 3 to 8 arms terminated with succinimidyl ester functional groups, wherein 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 having 3 to 8 arms terminated with protonated amine functional groups.

158. The medical patch of claim 157, wherein the succinimidyl ester functional group comprises N-hydroxysuccinimidyl succinate (SS), N-hydroxysulfosuccinimidyl succinate, N-hydroxysulfosuccinimidyl glutarate, succinimidyl glutarate (SG), succinimidyl adipate (SAP), succinimidyl azelate (SAZ), or a mixture thereof.

159. A method for forming a medical patch, the method comprising:

A structure comprising a biocompatible substrate and one or more hydrogel precursor layers is compressed to form the medical patch, wherein the one or more hydrogel precursor layers are melt-coated onto the substrate to present a surface along one side of the biocompatible substrate, wherein the biocompatible substrate comprises foamed gelatin having a broken pore structure, wherein the one or more hydrogel precursor layers at least partially extend into the broken pore structure of the biocompatible substrate to form a cohesive hydrogel precursor structure, wherein upon wetting with a physiological fluid or a physiological buffered saline, the cohesive hydrogel precursor structure cross-links to form a cohesive hydrogel structure.

160. The method of claim 159, wherein the compressing comprises calendering the structure.

161. The method of claim 160, wherein calendering is performed using calendering rolls having a gap of about 5% to about 70% of the thickness of the structure.

162. The method of any one of claims 159-161, wherein the one or more hydrogel precursor layers are at room temperature during the compressing.

163. The method of any one of claims 159-162, wherein the compressing breaks up the surface to form a fractured surface of the adhesive hydrogel precursor structure adhered to the biocompatible substrate.

164. The method of any one of claims 159-163, wherein the medical patch is more flexible and hydrates more rapidly than its pre-compression structure.

165. The method of any one of claims 159-164, wherein the medical patch is sufficiently flexible when dry that it can be wrapped around a ^1/2 _inch mandrel without breaking.

166. The method according to any one of claims 159-165, further comprising coating the biocompatible substrate with one or more hydrogel precursor layers prior to compression to form one or more hydrogel precursor layers coated on the substrate, wherein the coating comprises melt coating a dry blend of an electrophilic hydrogel precursor having multiple electrophilic functional groups and a nucleophilic hydrogel precursor having multiple nucleophilic functional groups.

167. The method of claim 166, wherein the biocompatible substrate prior to coating is sufficiently flexible that it can be wrapped around a ^1/2 _inch mandrel without breaking.

168. The method of claim 166, further comprising initially compressing the biocompatible substrate prior to coating.

169. The method of claim 168, wherein the initial compression comprises calendering the biocompatible substrate.

170. The method of claim 169, wherein calendering is performed using calendering rolls having a gap of about 5% to about 65% of the thickness of the biocompatible substrate.

171. The method of claim 168, wherein compressing the biocompatible substrate causes the pore structure of the foamed gelatin to rupture.

172. A method according to any one of claims 159-171, wherein the foamed gelatin is thermally cross-linked.

173. The method of any one of claims 168-171, further comprising thermally cross-linking the biocompatible substrate prior to initial compression.

174. A method for forming a medical patch, the method comprising:

applying a liquid hydrogel precursor to a porous hydrophilic substrate in a dry atmosphere, wherein the applying is performed by compressing the substrate at a printing position using a print head 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, wherein the liquid hydrogel precursor comprises a melt or non-aqueous solution of the electrophilic hydrogel precursor and/or the protected nucleophilic hydrogel precursor.

175. The method of claim 174, wherein the porous hydrophilic substrate comprises thermally cross-linked gelatin.

176. A method according to claim 174 or claim 175, wherein application is performed using a print head that compresses the substrate to a selected depth.

177. The method of claim 176, wherein the selected depth is from about 5% to about 30% of the thickness of the porous hydrophilic substrate prior to application.

178. The method of any one of claims 174-177, wherein the liquid hydrogel precursor comprises a blend of the electrophilic hydrogel precursor and the protected nucleophilic hydrogel precursor.

179. A method according to any one of claims 174-178, wherein the liquid hydrogel precursor comprises a first melt of the electrophilic hydrogel precursor and a second melt of the nucleophilic hydrogel precursor, wherein applying comprises applying the first melt and then applying the second melt, or applying the second melt and then applying the first melt.

180. The method of any one of claims 174-179, further comprising calendering the porous hydrophilic substrate prior to applying.

181. The method of any one of claims 174-180, further comprising calendering the medical patch after applying.

182. A method according to claim 181, wherein calendering includes a first calendering and a second calendering, wherein the first calendering is performed using a calendering roller having a first gap, and the second calendering is performed using a calendering roller having a second gap, wherein the second gap is smaller than the first gap.