JPH0240341B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel antithrombotic material. More specifically, the present invention relates to a medical material made of expanded polytetrafluoroethylene that has excellent antithrombotic properties and biocompatibility and is suitable for artificial blood vessels, artificial catheters, and the like.

BACKGROUND OF THE INVENTION In recent years, with the remarkable advances in medical care, various medical devices such as artificial blood vessels, vascular catheters, artificial kidney tubes, heart-lung machines, and blood bypass tubes have come into widespread use in areas that come into direct contact with blood. Ta.

Medical equipment used in areas that come into direct contact with blood must not only have good elasticity, durability, and wet toughness, but also have particularly excellent antithrombotic properties and biocompatibility. is necessary.

Therefore, the materials used for these medical devices are polymeric materials such as nylon, polyester, polyethylene, polypropylene, polyurethane, and fluororesin, which have antithrombotic properties and biocompatibility. .

Conventionally, methods for imparting antithrombotic properties to the above-mentioned polymeric materials include methods for making the material itself antithrombotic;
Known methods include mixing or chemically bonding a natural anticoagulant such as heparin to the material, and coating the surface of the material with collagen, which has excellent biocompatibility.

Among the above methods, examples of methods for making the material itself antithrombotic include using a special polyurethane compound to create a structure in which hydrophobic and hydrophilic parts alternately appear on the surface, or hydrogel or Some have a hydrophilic polymer bonded to a base polymer. However, although these polymeric materials exhibit fairly high antithrombotic properties, they are still insufficient for practical use, and no satisfactory material has yet been obtained.

In addition, as an example of a method for chemically bonding a natural anticoagulant such as heparin to a material, after graft polymerizing a vinyl compound having a tertiary amino group to a base polymer, Methods are known in which amino groups are quaternized and then heparinized. However, the polymeric material heparinized in this manner has the disadvantage that the desirable mechanical strength originally inherent in the base polymer is reduced, making it impossible to obtain the strength and durability required for practical use.

Furthermore, as an example of a method of coating the surface of a material with collagen, the surface of polyethylene, polypropylene, polyester, etc. is made hydrophilic by polarization treatment such as chromic acid mixture treatment or alkali treatment, and then collagen is applied. Then, the collagen is coated by irradiation with radiation (Japanese Patent Publication No. 46-37433), or the surface of the silicone rubber material is made hydrophilic by polarization treatment such as plasma glow discharge treatment or chemical treatment. Later, a method of coating collagen in the same manner as above (Japanese Patent Publication No. 49-4559) is mentioned. However, the polymeric material coated with collagen in this manner has insufficient antithrombotic properties and cannot be said to be necessarily satisfactory for medical use.

On the other hand, those using biomaterials such as collagen have better biocompatibility than the above-mentioned polymeric materials, but still have problems in terms of antithrombotic properties.

As described above, no medical material has been found to date that is fully satisfactory in terms of both antithrombotic properties and biocompatibility, and especially for grafted blood vessels with a diameter of 1 to 3 mm, rapid The reality is that nothing has yet been developed that can completely prevent the formation of blood clots.

The present inventors have conducted extensive research to obtain medical materials with excellent antithrombotic properties and biocompatibility, and first bonded mucopolysaccharide to the surface of a polymeric material activated by plasma glow discharge treatment. A heparin layer is further provided on the collagen layer provided on the surface of a polymeric material, and a heparin layer is further provided through a fibronectin layer, which is known as a cell adhesion protein, or on the surface of a polymeric material. We have developed a product in which antithrombotic mucopolysaccharides and collagen from which antigenic groups have been removed or a mixture of collagen or its gelatinized product are laminated and then cross-linked with a polyvalent aldehyde compound.

However, although these antithrombotic materials have considerably improved antithrombotic properties and biocompatibility compared to conventional materials, there is still a problem in satisfying both antithrombotic properties and biocompatibility at the same time. This was not necessarily sufficient, and further improvements were necessary.

Problems to be Solved by the Invention Under these circumstances, the purpose of the present invention is to provide a medical material such as an artificial blood vessel that has excellent antithrombotic properties and biocompatibility, and has good durability. The objective is to provide materials suitable for use as materials.

Means for Solving the Problems As a result of intensive research to develop an excellent antithrombotic material, the present inventors found that polytetrafluoroethylene has excellent mechanical properties such as elasticity and wet toughness, and Polytetrafluoroethylene, which has excellent compatibility, and especially stretched polytetrafluoroethylene, can easily penetrate into living tissues, making it suitable as a base material for antithrombotic materials. Focusing on the fact that saccharides have excellent antithrombotic properties, we have developed an expanded polytetrafluoroethylene base with at least one collagen layer on its surface, and a composite layer of collagen and mucopolysaccharides on top of that. The inventors have discovered that the above object can be achieved by providing the following, and have completed the present invention based on this knowledge.

That is, the present invention has a collagen layer on the surface of a stretched polytetrafluoroethylene base, and has a composite layer of collagen and mucopolysaccharide thereon,
The present invention also provides an antithrombotic material characterized in that the collagen is crosslinked with a crosslinking agent.

The present invention will be explained in detail below.

In the antithrombotic material of the present invention, stretched polytetrafluoroethylene is used as a base. When polytetrafluoroethylene is stretched, it has a fibrillated porous structure, into which biological tissues such as blood vessels and endothelial tissue can easily penetrate.

Porous expanded polytetrafluoroethylene having such a fibrillar structure is produced by, for example, mixing a liquid lubricant with a sintered powder of polytetrafluoroethylene and forming it into a desired shape by extrusion or rolling. It can be produced by uniaxially stretching the body as it is, or after removing the lubricant, and then heating it to a sintering temperature in a heat shrinkage-prevented state and fixing it by combustion (especially Kosho 42
-13560). The stretched polytetrafluoroethylene thus obtained has high strength and has a fibrillar structure consisting of extremely thin fibers and nodes interconnected by the fibers. The fiber diameter and length, and the size and number of nodules can be changed depending on the drawing and sintering conditions, so this can be used to freely determine the pore size and porosity of the drawn polytetrafluoroethylene. Can be done.

In addition to the above method, after forming a pre-sintered polytetrafluoroethylene composition containing a liquid lubricant into a desired shape, the lubricant is evaporated at an ambient temperature higher than the melting point of the polytetrafluoroethylene. A method that simultaneously handles the three steps of removal, stretching, and firing (Unexamined Japanese Patent Publication No. 1983-
178228), it is also possible to produce porous polytetrafluoroethylene having a fibrillar structure with improved strength.

There is no particular restriction on the shape of the stretched polytetrafluoroethylene used as the base of the present invention, and any shape such as sheet, tube, or rod can be selected.

In the antithrombotic material of the present invention, one or more highly biocompatible collagen layers are first provided on the surface of the expanded polytetrafluoroethylene base. In this case, in order to more firmly adhere the collagen layer to the surface, it is advantageous to activate the surface of the expanded polytetrafluoroethylene base in advance by plasma glow discharge treatment, if necessary. This plasma glow discharge treatment is performed by cleaning the surface of the expanded polytetrafluoroethylene base according to a conventional method, and then uniformly irradiating the surface with plasma generated by a plasma glow discharge generator. .

Methods for providing a collagen layer on the base surface include, for example, a method of applying a collagen aqueous solution having a concentration of 0.1 to 1% by weight to the surface of the stretched polytetrafluoroethylene, a method of soaking the stretched polytetrafluoroethylene in the collagen aqueous solution, When a collagen layer is provided on the inner surface of a container-like object or a tube-like object, the collagen aqueous solution is injected into them.
Methods such as evacuation are used.

In the present invention, the collagen layer thus provided is crosslinked with a crosslinking agent such as a polyhydric aldehyde compound such as glutaraldehyde or dialdehyde starch. This crosslinking treatment with a polyvalent aldehyde compound can be carried out in the same manner as described above by using, for example, a physiological saline solution containing 0.05 to 0.25% (V/V) glutaraldehyde to the stretched polytetrafluoroethylene base provided with the coating layer. This is done by processing.

This collagen layer may be provided in a single layer or in multiple layers, but in the case of providing multiple layers, the above-described process is repeated. At this time, collagen is
It is preferable to remove the antigenic group and use it with excellent biocompatibility. Collagen from which antigenic groups have been removed can be obtained, for example, by defatting bovine tendon or porcine tendon with enzyme lipase or the like, and then decomposing and removing antigenic peptides using enzyme pepsin or the like.

Next, a composite layer of collagen and mucopolysaccharide is provided on the collagen layer thus formed, but the mucopolysaccharide used for this composite layer is
For example, it has a disaccharide repeating unit consisting of an amino acid and uronic acid or glasstose,
This may or may not have a sulfate group. Mucopolysaccharides without sulfate groups include hyaluronic acid and chondroitin.
Mucopolysaccharides having sulfate groups include chondroitin sulfates such as chondroitin 4-sulfate, chondroitin 6-sulfate, and dermatan sulfate (chondroitin sulfate B), heparin, heparan sulfate, and keratan sulfate. These mucopolysaccharides have extremely excellent antithrombotic properties and also have good biocompatibility. In the present invention, heparin, hyaluronic acid, and chondroitin sulfate are particularly preferably used. Each of these mucopolysaccharides may be used alone, or
Two or more types may be used in combination.

Regarding the method for forming a composite layer of collagen and mucopolysaccharide, for example, collagen, preferably collagen 0.1 from which antigenic groups have been removed as described above, may be used.
~1.0% by weight and at least one mucopolysaccharide 0.05
A method in which an aqueous solution containing ~1.0% by weight is applied to the surface of the collagen layer, a method in which a stretched polytetrafluoroethylene base provided with the collagen layer is immersed in the aqueous solution, or a container-shaped or tube-shaped When forming on the collagen layer on the inner surface of objects, a method such as injecting and discharging the aqueous solution is used to form a complex layer of collagen and mucopolysaccharide on the collagen layer. At this time, if desired, the composite may be laminated into multiple layers by repeating such operations. Further, when preparing a mixed solution of collagen and mucopolysaccharide, two or more types of aqueous solutions using different mucopolysaccharides may be used and laminated in multiple layers.

It is also necessary that the thus formed composite layer of collagen and mucopolysaccharide be crosslinked with a crosslinking agent, such as a polyvalent aldehyde compound such as glutaraldehyde or dialdehyde starch. This crosslinking treatment using a polyvalent aldehyde compound is carried out in the same manner as the crosslinking treatment of the collagen layer, and by this crosslinking treatment, the obtained antithrombotic material has excellent durability.

This cross-linking treatment of collagen is carried out as described above.
The treatment may be performed for each of the collagen layer and the composite layer sequentially, or it may be performed simultaneously after providing the collagen layer and laminating the composite layer thereon.

Through such crosslinking treatment, the collagen becomes
It is cross-linked intermolecularly or intramolecularly or both. In addition, in the composite layer, mucopolysaccharides are thought to exist between crosslinked collagens in a chemically bonded state, physically dispersed state, or both, but in any case, The crosslinked composite layer has a composition in which collagen and mucopolysaccharide are mixed together.

Through such cross-linking treatment, the collagen layer,
In either case, the composite layer will be held in place by a liquid flowing within the tube, such as water or blood. On the other hand, if crosslinking treatment is not performed, membrane components will flow out, making it impossible to maintain antithrombotic biocompatibility and durability, which are the objectives of the present invention.

Next, the antithrombotic material of the present invention will be explained with reference to the accompanying drawings. The drawings are cross-sectional views of an example of an artificial blood vessel. It shows a state in which composite layers 3 with saccharides are sequentially laminated and crosslinked. When this artificial blood vessel is transplanted, blood first comes into contact with a complex layer of collagen and mucopolysaccharides, and albumin and other substances are adsorbed to its surface, forming stable plasma proteins. At this time, thrombus formation is inhibited by the mucopolysaccharides in the composite layer. Next, with the passage of time, this collagen and mucopolysaccharide complex layer undergoes sequential biodegradation, and finally a collagen layer with good tissue compatibility is exposed. At this stage, as the biological tissue grows and the collagen layer is further decomposed, a stable biological tissue layer with almost the same structure as the biological blood vessel surface membrane enters between the fibrils of the expanded polytetrafluoroethylene. , the quality of the artificial blood vessel is considered to be improved.

Effects of the Invention The antithrombotic material of the present invention has superior antithrombotic properties and biocompatibility compared to conventional materials. For example, in in vivo experiments using the abdominal aorta and abdominal vena cava of rats and rabbits, almost no thrombus formation was observed, and the endothelial cells necessary for long-term patency were well formed. Also,
Compared to conventional artificial blood vessels, their patency rate is extremely good when implanted in rats and rabbits, and therefore their survival period is significantly extended.

Since the antithrombotic material has excellent antithrombotic properties and biocompatibility, it can be used in addition to artificial blood vessels by appropriately changing the position where the composite layer is formed to a place where it comes into contact with blood. Various medical devices used in places that come into direct contact with blood, such as vascular catheters, artificial kidney tubes, heart-lung machines,
It is extremely useful as a medical material for blood bypass tubes, artificial heart pumping chambers, etc.

Examples Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Plasma glow discharge treatment was performed using a tube with an inner diameter of 2 mm made of stretched polytetrafluoroethylene with fibrils having an average length of 60 μm.

In order to effectively treat only the inner surface of the sample, this plasma glow discharge treatment was carried out using a 25 cm long Pyrex glass reaction tube with an inner diameter approximately 1 mm thicker than the outer diameter of the sample.

On the other hand, after solubilizing pig skin by pepsin treatment,
Collagen (2.5M NaCl precipitated component) was obtained by sequential fractionation using sodium chloride, and after dissolving it in an acetic acid aqueous solution (0.2N), dialysis with water was repeated to prepare a 0.4% by weight collagen aqueous solution.

The plasma glow discharge-treated tube was immersed in this collagen aqueous solution for 1 hour at room temperature, and then further immersed in a physiological saline solution containing 0.2% (V/V) glutaraldehyde to coat the surface of the tube. A collagen layer crosslinked with glutaraldehyde was provided.

Next, heparin was added to the collagen aqueous solution obtained as described above to prepare an aqueous solution containing 0.25% by weight of collagen and 0.1% by weight of heparin, and the tube provided with the collagen layer was immersed in this aqueous solution for 1 hour. Afterwards, the drying operation was repeated three times, and a layer in which a collagen/heparin complex was laminated was provided on the collagen layer.

Next, the tubes treated as described above were immersed in an aqueous solution of 15 g of dialdehyde starch dissolved in 10 parts of water for 30 minutes, dried, and washed with distilled water. Next, this product was immersed in a 30% by weight aqueous glycerin solution for 1 hour and then dried to obtain an artificial blood vessel with an inner diameter of 2 mm.

After sterilizing the artificial blood vessel thus obtained at 38°C for 6 hours using ethylene oxide gas, in vivo experiments using the abdominal aorta and abdominal vena cava of rats and rabbits, respectively, were performed. However, no thrombus was formed for at least 3 hours.

In addition, although it was thought that rats and rabbits could not survive for two months with conventional artificial blood vessels, some survived for longer than that.

Example 2 A tube with an inner diameter of 2 mm and a length of 2 cm was prepared from stretched polytetrafluoroethylene with fibrils having an average length of 60 μm.

On the other hand, beef tendon was degreased with lipase, then a mixture of acetone and ethanol was added to completely defatte it, the antigen groups were decomposed with pepsin under acidic conditions (pH approximately 2), and the pH was adjusted to pH 7 with Tris-HCl buffer. 4, then add sodium chloride to it until its concentration is
An amount of 0.9 mol/ml was added and centrifugation was performed.

Next, the supernatant was collected, and sodium chloride was added thereto to a concentration of 3 mol/ml to precipitate atelocollagen, which was fractionated. This atelocollagen was solubilized with 0.04N hydrochloric acid, and the viscosity
An acid-swollen atelocollagen solution was prepared by adjusting the pressure to 2500 cps (measured using a B-type viscometer).

The tube was immersed in this acid-swollen atelocollagen solution for 2 hours under vacuum and then dried, which was repeated to form an atelocollagen layer on the tube surface.

Next, 0.4% by weight of neutral range atelocollagen purified in the same manner as above and heparin sodium (1% by weight) were added.
A solution containing 173) 0.25% by weight of heparin units in mg was prepared, and this solution was poured into the tube provided with the atelocollagen layer. After drying, an atelocollagen-heparin composite layer was formed on the atelocollagen layer. Established.

The tube obtained in this way (a tube with two layers of atelocollagen and one layer of atelocollagen/heparin complex on the inside of the tube),
It was immersed in a solution of 3 g of dialdehyde starch dissolved in 1 part of water under negative pressure for 5 minutes to effect crosslinking, and then dried to obtain an artificial blood vessel. The inner thickness of this artificial blood vessel was 3.5 μm according to a scanning electron microscope.

The artificial blood vessel thus obtained was sterilized using ethylene oxide gas at 38°C for 8 hours, and then transplanted into the left cervical aorta of a rabbit. An artificial blood vessel with only a collagen layer was transplanted without a composite layer. Four weeks later, when the neck was opened, no thrombus was found in the left cervical aorta.

On the other hand, in the artificial blood vessel provided with only the atelocollagen layer, thrombus formation was observed over a length of about 4 mm from the artificial blood vessel inflow anastomosis.

Example 3 A stretched polytetrafluoroethylene tube (fibril length average 60 μm, inner diameter 1.5 mm, length 1 cm) was inserted into a glass rod with an outer diameter of 1.5 mm, and the acid purified and prepared as in Example 2 was added. A process of applying the swollen atelocollagen solution to the outside of the tube and drying it under vacuum was repeated twice to provide two laminated atelocollagen layers.

Add this to dialdehyde starch 0.3% solution.
After cross-linking, soak for 15 minutes, dry, then soak in distilled water for 30 minutes.
After soaking for a minute, the tube was pulled out from the glass rod.

Next, on the inside of this tube, two layers of atelocollagen and atelocollagen were added as in Example 2.
After laminating one heparin composite layer, it was crosslinked for 5 minutes with a 0.3% dialdehyde starch solution, dried, and washed several times with distilled water. Next, this product was sterilized with ethylene oxide to obtain an artificial blood vessel having an atelocollagen layer on the outside, an atelocollagen layer on the inside, and an atelocollagen/heparin composite layer layered thereon.

The artificial blood vessels thus obtained were transplanted into the abdominal aortas of each of the seven rats (10 months old).
As a result of laparotomy after 6 weeks, good formation of endothelial-like tissue was confirmed by macroscopic observation and histopathological examination in all cases.

On the other hand, another group of 7 rats (10
In cases in which the abdominal aorta was transplanted into each abdominal aorta and laparotomy was performed 6 weeks later, histopathological findings showed that the endothelium protruded from the anastomosis, and no endothelium was formed over the entire surface.

Example 4 Bovine tendon was defatted with lipase in the same manner as in Example 2, then further defatted with a mixture of acetone and ethanol, purified by decomposing and removing antigenic peptides using hepsin, and acid-solubilized. Atelocollagen was obtained. This acid-solubilized atelocollagen was dissolved in a dilute aqueous hydrochloric acid solution (PH2.2) to prepare a 0.5% by weight acid-swollen atelocollagen solution, and then a dilute aqueous sodium hydroxide solution was added dropwise to this solution while stirring to homogenize it on the weakly alkaline side. It became.

On the other hand, add 0.1 g of sodium hyaluronate and 1 g of sodium heparin to this atelocollagen solution.
An aqueous solution prepared by dissolving 0.2 g of heparin units (173) in mg in distilled water was added, the final volume was adjusted to 200 ml, and the mixture was sufficiently stirred to become homogeneous, followed by vacuum defoaming.

Next, a stretched polytetrafluoroethylene tube (fibril length average 60 μm, inner diameter 3 mm, length 5
In the same manner as in Example 2, the above atelocollagen solution was applied twice to the inner surface of the cm) and dried, and then the above sodium hyaluronate,
A solution consisting of sodium heparin and atelocollagen was applied twice, then crosslinked with dialdehyde starch, dried, and thoroughly washed with distilled water and dried. This material was sterilized with ethylene oxide to obtain an artificial blood vessel.

As a result of transplanting the artificial blood vessel obtained in this way into the cervical aorta of a dog, suturing at the anastomosis site was easy, and it had excellent flexibility and elasticity, and no thrombus was observed when the neck was opened 3 hours later. Nakatsuta.

Example 5 0.4% by weight of neutral range atelocollagen prepared in the same manner as in Example 2 and heparin sodium (1mg
A solution containing 0.25% by weight of heparin units (173) was poured into a stretched polytetrafluoroethylene tube (fibril length average 60 μm, inner diameter 2 mm, length 2 cm) under vacuum, and the process of drying was repeated. ,
I applied 3 layers. Next, this was immersed for 5 minutes in a solution in which 3 g of dialdehyde starch was dissolved in 1 part of water to perform crosslinking, thereby obtaining an artificial blood vessel. When this was stained with a basic dye and observed under a microscope, it was found that there were many uneven coatings, and it had the disadvantage of being non-uniform and easily peeling off.

Therefore, the acid-swollen atelocollagen solution in Example 2 was poured into the inside of the same stretched polytetrafluoroethylene tube as described above under vacuum, and the drying procedure was repeated again. A solution containing the above was applied under vacuum, and after drying, crosslinking was performed using a dialdehyde starch solution under the same conditions as above to obtain an artificial blood vessel.
When this was stained with a basic dye and observed under a microscope, it was found to be good with no peeling or unevenness.

That is, it was confirmed that the complex of atelocollagen and heparin has an affinity for biologically derived proteins, but does not show an affinity for stretched polytetrafluoroethylene.

[Brief explanation of drawings]

The figure is a cross-sectional view of one example of an artificial blood vessel made of the antithrombotic material of the present invention, in which reference numeral 1 is a stretched polytetrafluoroethylene tube having a fibrillar structure;
2 is a collagen layer, and 3 is a composite layer of collagen and mucopolysaccharide.

Claims (1)

[Claims] 1. On the surface of the stretched polytetrafluoroethylene base,
An antithrombotic material comprising a collagen layer, a collagen and mucopolysaccharide composite layer thereon, and the collagen being crosslinked with a crosslinking agent. 2. The antithrombotic material according to claim 1, wherein the crosslinking agent is a polyaldehyde compound. 3. The antithrombotic material according to claim 2, wherein the polyaldehyde compound is at least one of glutaraldehyde and dialdehyde starch. 4 The mucopolysaccharide is at least one selected from heparin, hyaluronic acid, and chondroitin sulfate.
The antithrombotic material according to claim 1, which is a species.