JP3014325B2 - Artificial blood vessel and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an artificial blood vessel,
More specifically, the present invention relates to an artificial blood vessel used for treating diseases such as aorta, coronary arteries, and peripheral blood vessels.

[0002]

2. Description of the Related Art Conventionally, woven or knitted polyester fiber or drawn polytetrafluoroethylene (hereinafter referred to as eP
TFE) tubes are used as artificial blood vessels.
The ePTFE tube is made of an artificial blood vessel having a smaller diameter than polyester, because polytetrafluoroethylene itself is excellent in antithrombotic properties and the porous structure comprising fibers and nodules obtained by stretching is excellent in biocompatibility. Has been applied to

However, ePTFE does not have sufficient antithrombotic properties, and a sufficient patency rate has not been obtained with artificial blood vessels having an inner diameter of 5 mm or less, particularly 4 mm or less. Therefore, as a method of solving these, a method of increasing the antithrombotic property of the material itself, a method of devising to promote the formation of antithrombotic tissue on the inner surface after transplanting an artificial blood vessel, A method of culturing (seeding) is studied.

[0004]

Specifically, as a method, the development of an antithrombotic polymer material having a microphase-separated structure and a material for immobilizing an antithrombotic agent has been studied (Noiro et al., Transaction Of the Asio (Trance.AS)
AIO), 23 , 253 (1977)). As an example of the method, an artificial blood vessel obtained by applying a cell-adhesive protein such as collagen or fibronectin and then cross-linking has been proposed (Lundgren et al., Transactions of Asio, 32 , 346 (1986)). As a method of (1), a method of seeding vascular endothelial cells on the inner surface of an artificial blood vessel has been studied (Takagi et al., Artificial Organ, 17 , 679,
(1988), JP-A-1-170466).

[0005] However, this method has a problem that it is difficult to secure human vascular endothelial cells and it takes several weeks to culture. We have developed ePTFE
A similar study was performed by combining surfaces with various materials and conditions. As a result, simply combining an antithrombotic material or a tissue-inducing substance over the entire surface of ePTFE does not provide the effect advocated for the drug to be used, and the conventional patency without any treatment is performed. It was less than or equal to ePTFE.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an ePTFE tube having a structure in which a certain amount of blood enters the inner wall immediately after transplantation, for example, an ePTFE tube having a structure in which half of the wall has been hydrophilized. The patency was found to increase the patency compared to ePTFE tubes not subjected to such treatment, and furthermore, if an antithrombotic substance or cell adhesive protein was complexed to this hydrophilized layer, the patency of the drug could be improved. We found that we can bring out the effect effectively. In addition, it has been found that in order to further increase the patency rate, an antithrombotic substance or a tissue-inducing substance may be immobilized on the hydrophilized layer.

That is, the present invention renders a layer comprising a porous tube of expanded polytetrafluoroethylene having a depth from the inner surface in the range of 5% to less than 96% of the wall thickness hydrophilic, and optionally hydrophilic. An artificial blood vessel in which at least one substance selected from the group consisting of an antithrombotic substance and a biological tissue-inducing substance is immobilized on a layer, a porous tube of expanded polytetrafluoroethylene, and a part of the wall thickness from the outer surface thereof Provided is an artificial blood vessel in which a portion not impregnated with a thermoplastic substance is subjected to a hydrophilic treatment after infiltration of the thermoplastic substance, and a method for producing the same.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In order to form a strong bond between a living blood vessel and an artificial blood vessel at an anastomosis portion at an early stage, eP
It is desirable that the fiber length of TFE is 20 to 200 μm and the porosity is 50% or more, preferably 70% or more. In addition, the wall thickness of the ePTFE tube may be selected from 300 to 1000 μm in order to match a living blood vessel.

As a method for chemically introducing a hydrophilic group within a certain depth from the inner surface of the ePTFE tube, the following method can be exemplified. After masking a certain depth range from the outer surface of the ePTFE tube with paraffin or the like having affinity for PTFE, a chemical treatment using an alkali metal, or radiation emission such as γ-ray or electron beam, corona discharge, glow discharge The non-masked portion of ePTFE is defluorinated by a physical treatment such as a treatment, and then a functional group is introduced by loading a compound having a carboxyl group, a hydroxyl group, an amino group, an epoxy group, etc. in the molecule, and then masking. Remove the material used for.

At this time, in order to increase the patency rate, the thickness of the portion not masked by paraffin or the like should be 5% to 95%, preferably 50% to 90% of the wall thickness. preferable. This thickness control preferably takes advantage of the fact that changing the temperature gradient in the wall by controlling the temperature of the cooling water flowing through the tube lumen changes the depth of penetration of the melted paraffin. Alternatively, the paraffin on the lumen side is extracted with a solvent after permeation of the paraffin into the entire wall.

As the alkali metal compound used for the chemical treatment, for example, methyl lithium, n-butyl lithium, t
-Butyl lithium, sodium-naphthalene, naphthalene-benzophenone, vinyl lithium and the like,
These are used as solutions. Sodium-naphthalene or sodium-benzophenone can be converted to P
Since it is difficult to form a black-brown layer on the TFE surface and to perform uniform treatment, it is preferable to use methyllithium, n-butyllithium, and t-butyllithium in order to form the artificial blood vessel of the present invention. . Methyl lithium,
Since n-butyllithium and t-butyllithium themselves have a weak effect of extracting fluorine, it is necessary to add a chelating reagent such as hexamethylphosphoric triamide or N, N, N, N-tetramethylethylenediamine. is there.

Examples of the substance containing a hydroxyl group, carboxyl group, epoxy group or amino group in the molecule include glycerol (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol ( Examples thereof include (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylic acid, allylamine, 2-aminoethyl (meth) acrylate, and acrylamide. Alternatively, an anhydride such as maleic anhydride may be added, followed by hydrolysis.

More specifically, PT
The FE tube is immersed in a diethyl ether solution of methyllithium, hexamethylphosphoric acid triamide is added thereto, and left at -10 ° C for 30 minutes to extract fluorine atoms of PTFE, and then the reaction solution is removed. An aqueous solution of acrylic acid is added thereto and reacted at 80 ° C. for 10 hours. After the reaction, excess acrylic acid and its polymer can be washed away to obtain an acrylic acid graft.

In order to introduce these functional groups into the PTFE, irradiation with gamma rays or electron beams or glow discharge may be used. However, according to the known fact, in the treatment with radiation, PTFE is decomposed to the inside of the PTFE crystal, so that the molecular weight of PTFE is reduced and the strength is remarkably reduced, so that it is difficult to practically use it as an artificial blood vessel. In the glow discharge treatment, it is difficult to treat the inside of the porous PTFE.

On the other hand, when treated with an alkali metal compound, only the very surface layer having a thickness of about several hundred angstroms is treated, so that the strength of the tube is not reduced, and even if a porous material such as ePTFE is used. It is possible to process uniformly.

In order to fix the antithrombotic substance and / or the tissue-inducing substance, it may be simply applied physically, or may be chemically bonded to a functional group introduced in advance. If the target substance does not lose its activity even by chemical bonding, it is more preferable to use a method of chemically bonding to the introduced functional group. As the method, a method suitable for the functional group may be selected, and preferably, a method that does not lose activity by immobilization may be selected.

For example, a covalent bond is formed by a dehydration condensation for a hydroxyl group, a carboxyl group and an amino group, and by an addition reaction for an epoxy group. The hydroxyl group may be directly bound by dehydration condensation using carbodiimide as a catalyst, or a leaving group such as a trifluoromethanesulfonyl group may be introduced into the hydroxyl group to increase the reactivity and then increase the reactivity of the tissue inducing substance. It may be reacted with an amino group. Further, the carboxyl group may be directly bound using a dehydration condensation catalyst such as carbodiimide, or may be reacted with N-hydroxysuccinimide to introduce an active ester to increase the reactivity, thereby enhancing the reactivity. It may be reacted with an amino group of a thrombotic substance or a tissue-inducing substance.

Examples of the antithrombotic substance to be complexed include anticoagulants such as hirudin and heparin, plasminogen activators such as t-PA and urokinase, fibrinolytic enzymes such as plasmin and subtilisin, and prostacyclin and aspirin. Although an antiplatelet agent may be used, heparin is particularly preferred. The fixed amount is 300
２０００2000 μg (about 60-400 units) is good.

As the tissue-inducing substance to be complexed, a protein having cell adhesion such as collagen, gelatin, laminin and fibronectin may be used, and fibronectin is particularly preferable. The fixed amount is 1cm tube
Per unit, 50 μg to 500 μg is good.

By the above treatment, expanded PTFE
The depth from the inner surface of the tube consisting of 5% or more of the wall thickness 96
% Is obtained, and an artificial blood vessel having improved patency, in which an antithrombotic substance and / or a tissue-inducing substance is fixed to a layer into which the hydrophilic group is introduced, in a layer having a hydrophilicity of less than 10%. .

[0021]

EXAMPLES The fiber length of ePTFE described in the following Examples and Comparative Examples is the average value of the distance between nodules measured by a scanning electron microscope. Next, the present invention will be described specifically with reference to examples, but the scope of the present invention is not limited by these examples. Example 1 Inner diameter 2.0 mm, outer diameter 3.0 mm, length 20 mm, average fiber length 3
After impregnating with paraffin to a depth of about 50 μm from the outer surface of an ePTFE tube having 0 μm and a porosity of 75%,
Under an argon atmosphere at 0 ° C., 20 ml of a methyllithium ether solution (1.4 M) and 2 ml of hexamethylphosphoramide were added.
For 30 minutes. Thereafter, only the solution was removed, and a solution of acrylic acid (1 g) in water (20 ml) was added.
For 10 hours. Next, acrylic acid and paraffin polymerized with excess acrylic acid were washed away to obtain an acrylic acid-grafted ePTFE tube. As calculated from the weight change, the graft amount of acrylic acid was about 235 μg / cm of the tube.

Example 2 Inner diameter 2.0 mm, outer diameter 3.0 mm, length 20 mm, average fiber length 3
After impregnating with paraffin to a depth of about 100 μm from the outer surface of an ePTFE tube having 0 μm and a porosity of 75%,
Under an argon atmosphere at 10 ° C., 20 ml of a methyllithium ether solution (1.4 M) and 2 m of hexamethylphosphoramide were added.
of the mixed solution for 30 minutes. Thereafter, only the solution was removed, and a solution of 1 g of acrylic acid in 20 ml of water was added.
The reaction was performed at 10 ° C. for 10 hours. Next, acrylic acid and paraffin polymerized with excess acrylic acid were washed away to obtain an acrylic acid-grafted ePTFE tube. As calculated from the change in weight, the amount of grafted acrylic acid was about 195 μg per cm of the tube.

Example 3 Inner diameter 2.0 mm, outer diameter 3.0 mm, length 20 mm, average fiber length 3
After impregnating paraffin to a depth of about 300 μm from the outer surface of an ePTFE tube having 0 μm and a porosity of 75%,
Under an argon atmosphere at 10 ° C., 20 ml of a methyllithium ether solution (1.4 M) and 2 m of hexamethylphosphoramide were added.
of the mixed solution for 30 minutes. Thereafter, only the solution was removed, and a solution of 1 g of acrylic acid in 20 ml of water was added.
The reaction was performed at 10 ° C. for 10 hours. Next, acrylic acid and paraffin polymerized with excess acrylic acid were washed away to obtain an acrylic acid-grafted ePTFE tube. As calculated from the change in weight, the graft amount of acrylic acid was about 90 μg per cm of the tube.

Example 4 Inner diameter 2.0 mm, outer diameter 3.0 mm, length 20 mm, average fiber length 3
After impregnating with paraffin to a depth of about 480 μm from the outer surface of an ePTFE tube having 0 μm and a porosity of 75%,
Under an argon atmosphere at 10 ° C., 20 ml of a methyllithium ether solution (1.4 M) and 2 m of hexamethylphosphoramide were added.
of the mixed solution for 30 minutes. Thereafter, only the solution was removed, and a solution of 1 g of acrylic acid in 20 ml of water was added.
The reaction was performed at 10 ° C. for 10 hours. Next, acrylic acid and paraffin polymerized with excess acrylic acid were washed away to obtain an acrylic acid-grafted ePTFE tube. As calculated from the change in weight, the graft amount of acrylic acid was about 20 μg per 1 cm of the tube.

Example 5 The same tube as in Example 3 was replaced with 0.5% heparin (SANO).
After immersion in an aqueous solution (FI company) for 10 minutes, it was freeze-dried to obtain a heparin-complexed ePTFE tube. Calculated from the change in weight, the amount of immobilized heparin was
It was about 550 μg per cm.

Example 6 0.05% fibronectin (derived from bovine plasma, Nippon Ham)
And an aqueous solution of 0.5% 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide was adjusted to pH 5 with 1N hydrochloric acid, and the acrylic acid-grafted ePTFE prepared in Example 3 was immersed in this solution for 24 hours. Thereafter, the resultant was washed with water to obtain fibronectin-bound ePTFE. As calculated from the change in weight, the amount of bound fibronectin was 160 μg per cm of the tube.

Example 7 In Example 6, fibronectin-bound ePTFE tube was placed in a 0.5% heparin (SANOFI) aqueous solution for 10 minutes.
And then freeze-dried to give heparin-complexed ePTFE.
A tube was obtained. Calculated from the weight change, the amount of immobilized heparin was about 550 μg / cm tube.
Met.

Comparative Example 1 Inner diameter 2.0 mm, outer diameter 3.0 mm, length 20 mm, average fiber length 3
An ePTFE tube having 0 μm and a porosity of 75% was used as an artificial blood vessel as it was. .

Comparative Example 2 Inner diameter 2.0 mm, outer diameter 3.0 mm, length 20 mm, average fiber length 3
An ePTFE tube having a pore size of 0 μm and a porosity of 75% was placed in an ether solution of methyllithium (1.4%) under an argon atmosphere.
M) It was immersed in a mixed solution of 20 ml and 2 ml of hexamethylphosphoramide for 30 minutes. Thereafter, only the solution was removed, a solution of 1 g of acrylic acid in 20 ml of water was added, and the mixture was reacted at 80 ° C. for 10 hours. Next, the acrylic acid polymerized with the excess acrylic acid is washed and removed, and acrylic acid grafted ePTFE is removed.
A tube was obtained. When calculated from the weight change, the amount of grafted acrylic acid was about 250 μg per cm of tube.
Met.

Comparative Example 3 The same tube as in Comparative Example 2 was replaced with 0.5% heparin (SANO).
After immersion in an aqueous solution (FI company) for 10 minutes, it was freeze-dried to obtain a heparin-complexed ePTFE tube. Calculated from the change in weight, the amount of immobilized heparin was
It was about 920 μg per cm.

Comparative Example 4 An aqueous solution of 0.05% fibronectin (derived from bovine plasma, Nippon Ham) and 0.5% 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide was added with 1N hydrochloric acid to give p.
After adjusting to H5, the acrylic acid grafted ePTFE tube manufactured in Comparative Example 2 was immersed in this solution for 24 hours, and then washed with water to obtain a fibronectin-bound ePTFE tube. As calculated from the change in weight, the amount of bound fibronectin was 290 / cm
μg.

Comparative Example 5 The fibronectin-bound ePTFE tube prepared in Comparative Example 4 was immersed in a 0.5% heparin (SANOFI) aqueous solution for 10 minutes, lyophilized, and dried.
Heparin-conjugated ePTFE was obtained. Calculated from the weight change, the amount of immobilized heparin was about 920 μg / cm tube.

Comparative Example 6 Inner diameter 2.0 mm, outer diameter 3.0 mm, length 20 mm, average fiber length 3
Paraffin was impregnated to a depth of about 20 μm from the outer surface of an ePTFE tube having 0 μm and a porosity of 75%. Thereafter, the mixture was immersed in a mixed solution of 20 ml of a methyllithium ether solution (1.4 M) and 2 ml of hexamethylphosphoramide for 30 minutes at -10 ° C. in an argon atmosphere, and only the solution was removed. Medium solution and add 80
The reaction was performed at 10 ° C. for 10 hours. Thereafter, acrylic acid and paraffin, which were polymerized with excess acrylic acid, were washed away to obtain an acrylic acid graft. When calculated from the change in weight,
The graft amount of acrylic acid is about 250 per cm of tube.
μg.

Each of the artificial blood vessels produced in Examples and Comparative Examples was replaced and transplanted into the carotid artery of a rabbit, and the patency rate after one week and one month was examined. Table 1 shows the results. As is clear from these results, the thickness of the hydrophilic layer was 5% of the wall thickness.
The patency rate of the artificial blood vessel, which is from 95% to 95%, is higher than the patency rate of the untreated ePTFE tube, and the patency rate of the artificial blood vessel provided with the hydrophilic layer in about half of the entire wall is the highest. it was high. In addition, it can be seen that the patency rate of the tube coated with an antithrombotic agent is good at the initial stage, and that the conjugated cell adhesion protein increases the patency ratio in a long term. In addition, the composite of both the antithrombotic agent and the cell adhesive protein resulted in a higher patency rate from the beginning to a longer period than any other artificial blood vessel. By the way, those in which a hydrophilic group is introduced into the entire surface and complexed with an antithrombotic agent or a cell adhesive protein have a poor patency rate.

[0035]

[Table 1]

[0036]

The tube of expanded polytetrafluoroethylene (hereinafter abbreviated as PTFE) has been used as an artificial blood vessel. However, this material itself does not have sufficient antithrombotic properties. In particular, in the small-diameter region having an inner diameter of 4 mm or less, occlusion due to thrombus frequently occurs. According to the present invention, an artificial blood vessel into which a hydrophilic group is chemically introduced and a layer into which the hydrophilic group is introduced are provided with an antithrombotic substance or a tissue-inducing substance at a depth of 5 to 95% of the wall thickness from the inner surface of the ePTFE tube. Physical or chemical immobilization of a substance increases patency.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-200656 (JP, A) JP-A-60-99259 (JP, A) JP-A-63-46169 (JP, A) JP-A-5-2006 269198 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61L 33/00 A61F 2/06 A61L 27/00

Claims (3)

(57) [Claims] 1. A porous tube of expanded polytetrafluoroethylene, wherein the depth from the inner surface is 5% of the wall thickness.
An artificial blood vessel in which a layer in a range of at least 96% is made hydrophilic. 2. A stretched polytetrafluoroethylene porous tube, whose depth from the inner surface is 5% of the wall thickness.
An artificial blood vessel in which a hydrophilic group is introduced into a layer in a range of at least 96% and at least one substance selected from the group consisting of an antithrombotic substance and a biological tissue-inducing substance is fixed to the layer. 3. A stretched polytetrafluoroethylene porous tube, wherein a thermoplastic material is impregnated from the outer surface of the porous tube into a part of the wall thickness, and a portion not impregnated with the thermoplastic material is subjected to hydrophilic treatment. Method for producing an artificial blood vessel.