JPH10234846A - Anti-thrombus material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable prolonged gradual elimination with a prevention of reduction in activity by applying a coating of a material with an anti-thrombus substance immobilized on a base material through a hydrophilic substance on the surface of fine grains indicating decomposability in vivo to increase the degree of immobilization of the thrombus substance. SOLUTION: A material which is decomposed to produce matters unharmful to a human body, for example, polyalkylcyanoacrylate based polymer is used to form fine grains decomposable in vivo. An anti-thrombus substance is immobilized on the fine grains through a hydrophilic substance which has at least one functional group that allows bonding of a functional group able to immobilize the anti-thrombus substance to the fine grains decomposable in vivo in one molecule. The hydrophilic substance herein used is, for example, polyalkyl glycol or the like having a carboxyl group at both terminals thereof. This can prevent a drop in the activity of the anti-thrombus substance thereby enabling prolonged gradual elimination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material that imparts antithrombotic properties to the surface of a material that comes into contact with blood, such as a medical device or a surgical device. More specifically, the present invention relates to a material that imparts antithrombotic properties to the surface of artificial blood vessels, catheters, artificial hearts, artificial kidneys, and the like.

[0002]

2. Description of the Related Art A technique for imparting blood compatibility to a material surface of a medical device involves immobilizing a fibrinolytic substance typified by a heparin-like substance or urokinase on a base material by some method. (Japanese Patent Publication No. 7-265405, Japanese Patent Publication No. 60-10734) Immobilization of an antithrombotic substance on a substrate is performed directly on the surface by using a functional group of the substrate on which the antithrombotic substance is easily immobilized. Alternatively, it is performed through a specific substance. When the antithrombotic substance is immobilized on the surface of the base material by the method described above, the antithrombotic substance is present on the surface of the material and exhibits antithrombotic properties. However, since the reaction is performed on the surface of the base material, it is difficult to perform an immobilization operation into a complicated shape, and there are problems such as an insufficient amount of the immobilization and a decrease in the activity of the antithrombotic substance due to enzymes in blood during use. In order to solve the problems of decreased activity of the antithrombotic substance due to enzymes in the blood, restriction of the movement of the antithrombotic substance by immobilization, and reduction of the activity efficiency due to the orientation of the active site, the antithrombotic substance was removed from the material surface. Techniques for maintaining antithrombotic properties by sustained release have been developed. In this case, the loading of the antithrombotic substance is carried out by ionic bonding between the antithrombotic substance and the surface of the substrate, or by coating the substrate with the antithrombotic substance together with a matrix material.

[0003] The mechanism of sustained release of the antithrombotic substance by ionic bonding between the antithrombotic substance and the substrate surface is an ion exchange reaction between the antithrombotic substance and blood ions or proteins. (JP-A-4-
No. 298523) The ion exchange reaction between an antithrombotic substance and blood ions or proteins is an ion exchange reaction between one molecule of the antithrombotic substance and a plurality of blood substances and is complicated. The release mechanism is based on the ion exchange reaction, so that the ions in the blood are randomly adsorbed on the substrate, and the antithrombotic substance is exposed on the substrate. It becomes a problem. When the antithrombotic substance is dispersed in the polymer matrix, the mechanism of sustained release of the antithrombotic substance is swelling or hydration due to the matrix material coming into contact with the blood, dissolution of the antithrombotic substance in the matrix, and diffusion into the matrix. . In this case, there is a problem that the slow release period of the antithrombotic substance is short because the diffusion rate of the antithrombotic substance in the matrix is high. Unfortunately, antithrombotic materials with a satisfactory surface in terms of sustained release rate, duration and antithrombotic properties have not yet been developed to date.

[0004]

SUMMARY OF THE INVENTION The present invention provides an antithrombotic material having a surface capable of maintaining antithrombotic properties for a long period of time by increasing the amount of immobilized antithrombotic substance and increasing the activity of the antithrombotic substance. The purpose of this study was to prevent the decrease and to enable long-term sustained release of antithrombotic substances.

[0005]

The present invention relates to a technique for coating biodegradable fine particles carrying an antithrombotic substance on a base material of a medical device to form a fine particle layer to impart antithrombotic properties. is there. That is, a material in which an antithrombotic substance is immobilized via a hydrophilic substance on the surface of a biodegradable microparticle is coated on a substrate, or the antithrombotic substance is dispersed in the biodegradable microparticle. It is an antithrombotic material obtained by coating a material on a substrate and imparting antithrombotic properties to the surface of the substrate.

In the case where the antithrombotic substance is supported on the surface of biodegradable particles, the surface area that can be immobilized is increased by supporting the antithrombotic substance on a spherical surface instead of a flat surface, thereby increasing the amount of immobilization. It becomes possible. Since the antithrombotic substance is not immobilized directly on the base material and is bound to biodegradable microparticles to coat the surface of the base material, the antithrombotic treatment operation of a complicated shape is applied to the base material solution. Thus, the loss of the antithrombotic substance can be reduced as compared with the method of immersion reaction. Since the microparticles have biodegradability, the microparticles on the surface of the base material are gradually decomposed, the antithrombotic substance with reduced activity is discharged, and the antithrombotic substance whose activity is maintained is immobilized on the surface. The appearance of the fine particles on the surface of the substrate maintains an excellent antithrombotic surface. Further, since the antithrombotic substance is immobilized on the surface of the fine particles via the hydrophilic substance, the motility of the antithrombotic substance is not restricted, and the decrease in the activity can be suppressed.

When an antithrombotic substance is carried in particles, the antithrombotic substance is released by the decomposition of the fine particles in a living body. The sustained release rate of the antithrombotic substance is controlled according to the degradability of the microparticles in the living body. The advantage of micronization is that the antithrombotic substance can be uniformly supported on the fine particle layer on the substrate, and the antithrombotic treatment operation into a complicated shape can be performed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

1) Immobilization of antithrombotic substance on biodegradable microparticle surface First, biodegradable microparticles having a hydrophilic substance on the surface are prepared. The substance serving as the particle core of the biodegradable fine particles is a polyalkylcyanoacrylate-based polymer, or polylactic acid, a polylactic acid-polyglycolic acid copolymer, or a polyamino acid-based substance whose decomposition products are harmless to the human body So desirable. The hydrophilic substance is desirably a substance having at least one functional group capable of immobilizing an antithrombotic substance and one functional group capable of binding to biodegradable fine particles in one molecule. For example, both terminal carboxyl group type polyalkyl glycol, both terminal amino group type polyalkyl glycol and the like. More preferably, a substance having functional groups having different reaction properties at both ends is desirable. For example, one terminal carboxyl group and other terminal amino group type polyalkyl glycol, one terminal methacryloyl type and other terminal carboxyl group type polyalkyl glycol can be used.

The biodegradable fine particles can be prepared by radical polymerization, anion polymerization or the like when the monomer is a vinyl type. When a solvent is appropriately selected, a vinyl-terminated hydrophilic substance and a biodegradable monomer serving as a particle nucleus are added to carry out dispersion polymerization, fine particles having a hydrophilic substance on the surface are obtained. In the case of a condensed type biodegradable substance, the biodegradable substance is first polymerized, and the aqueous solution is dispersed in oil and reacted with the hydrophilic substance while heating, whereby fine particles having hydrophilic molecules on the surface are obtained. Can be The particle size of the fine particles obtained as described above can be controlled by changing the hydrophobicity of the monomer, the molecular weight of the hydrophilic substance, the charge ratio of the hydrophilic substance to the biodegradable substance during preparation, and the like. Yes, about 0.05 to 500 μm. The particle size and the degree of hydrophobicity of the biodegradable material govern the decomposition rate of the fine particles, and the decomposition rate of the fine particles can be controlled by the charge ratio of the material, which can be used for controlling the decomposition rate of the material surface. The method of immobilizing the antithrombotic substance on the obtained fine particles is performed according to the functional group. There are many known methods for immobilizing an antithrombotic substance, and these methods are followed. Basically, after activating the functional group of the hydrophilic substance on the surface of the fine particles, centrifugation is performed several times to wash the particles. An antithrombotic substance to be redispersed and immobilized in a buffer is added and reacted.
The antithrombotic substance is not particularly limited, but examples include heparin, sulfated polysaccharide, urokinase, thrombomodulin, streptokinase, lambolokinase and the like. After the reaction, the unreacted substances are washed by centrifugation to complete the immobilization.

2) When an antithrombotic substance is carried inside the biodegradable fine particles: The substance serving as the core of the biodegradable fine particles is a polyalkylcyanoacrylate polymer or polylactic acid.
Polylactic acid-polyglycolic acid copolymers and polyamino acid-based substances are desirable because their decomposition products are harmless to the human body. Preparation of biodegradable microparticles can be prepared by radical polymerization, anion polymerization or the like when the monomer is a vinyl type. A suitable solvent is selected, and a vinyl-terminated hydrophilic substance, potassium persulfate, a biodegradable monomer serving as a particle nucleus, and an antithrombotic substance are added, and dispersion polymerization is performed. The substance is loaded. In the case of a condensed type biodegradable substance, the biodegradable substance is first polymerized, then mixed with an antithrombotic substance, and adjusted by a spray drying method, a submerged drying method or the like.

The control of the particle size of the fine particles obtained as described in 1) and 2) is carried out by changing the hydrophobicity of the monomer, the charge ratio at the time of preparing the hydrophilic substance and the biodegradable substance, or the drying conditions. And it is about 0.05 to 500 μm. The particle size and the degree of hydrophobicity of the biodegradable material govern the decomposition rate of the fine particles, and the decomposition rate of the fine particles can be controlled by the charge ratio of the material, which can be used for controlling the decomposition rate of the material surface. The formation of the biodegradable fine particle dispersion layer on the base material is performed by directly applying the concentration of the biodegradable fine particle dispersion having the antithrombotic substance immobilized thereon or by centrifugation, and applying the concentrate on the base material. I can do it. For coating on the medical device substrate, a fine particle dispersion may be used as it is, or a coating solution in which a polymer serving as a matrix is dissolved and mixed may be used.
The polymer serving as the matrix is not particularly limited, but is preferably a hydrophilic polymer having excellent blood compatibility, such as polyethylene glycol, a polymethacrylate derivative, and polyvinyl alcohol. The thickness of the fine particle layer can be controlled by the concentration of the dispersion of the biodegradable fine particles.

[0012]

【Example】

(1) Preparation of biodegradable fine particles (A) Preparation of biodegradable fine particles having immobilized heparin 10 g of 2-cyanoacrylate (manufactured by Sigma) and 1 g of methacryloyl-type carboxyl group at one end and 1 g of polyethylene glycol at the other end Was dissolved in a solvent of ethanol: water = 1: 1, and dispersion polymerization was carried out at 60 ° C. for 10 hours using azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) as an initiator. After completion of the reaction, purification was performed by dialysis and centrifugation.
Observation of the morphology and measurement of the diameter of the obtained fine particles by SEM revealed that the shape was spherical and the average diameter was 200 nm. The aqueous dispersion of fine particles obtained as described above (0.1 g
/ ml) by centrifugation, and 0.1 g of water-soluble carbodiimide (manufactured by Wako Pure Chemical Industries, Ltd.) was added to activate the carboxyl groups of the fine particles at 4 ° C for 30 minutes. Thereafter, excess water-soluble carbodiimide was removed by centrifugation. Next, heparin (manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution (0.1 g / ml) 10 m
l was added and the reaction was carried out at 4 ° C. for 24 hours. After the reaction,
Unreacted heparin was removed by centrifugation. The amount of heparin immobilized was calculated from the weights of the particles before and after the reaction and found to be 1 g / g per fine particle weight.

(B) Preparation of biodegradable fine particles carrying heparin in particles 1 g of heparin was dissolved in 10 ml of water and dropped into 100 ml of ethanol to form fine particles of heparin. Next, a solution was prepared by dissolving 10 g of 2-cyanoacrylate (manufactured by Sigma) and 1 g of methacryloyl-type other-end carboxyl group polyethylene glycol at 100 g of water in 100 ml of water. Nitrile (Wako Pure Chemical Industries, Ltd.)
Was subjected to dispersion polymerization at 60 ° C. for 10 hours.
After completion of the reaction, purification was performed by dialysis and centrifugation. Observation of the morphology and measurement of the diameter of the obtained fine particles were carried out by SEM. As a result, the shape was spherical and the average diameter was 800 nm.

(2) Coating of fine particles on a substrate A fine particle aqueous dispersion (0.2 g / ml) prepared by coating the fine particle layer inside a polyurethane (TECOFLEX) tube (inner diameter 1 mm) in (1) (A). Was performed using a syringe.
The aqueous dispersion of the fine particles was inserted into a polyurethane tube, discharged, and dried under vacuum to perform coating. The thickness of the coating layer measured by an electron microscope was 5 μm.

(3) Decomposition rate test of the fine particle layer The decomposition test of the fine particle layer was performed on the tube prepared in (2).
This was carried out by circulating a phosphate buffer (pH = 7.4) maintained at a temperature of ° C using a pump. The tube was cut off at predetermined time intervals, and after drying under vacuum, the thickness of the fine particle layer was measured using an electron microscope. The results are shown in FIG.

(4) Evaluation of antithrombotic properties by animal implantation One adult beagle dog (female) weighing 12 kg was pretreated with atropine, and induction of anesthesia was performed with flunitrazepam 0.1 mg / kg.
Was performed by intravenous injection of ketamine 3 mg / kg. After fixing the dog on an operating table, heparin (100 U / kg) was intravenously injected, and the neck was incised while maintaining anesthesia with Frosen to expose both left and right carotid arteries by about 5 cm each. Subsequently, the left carotid artery was temporarily ligated, and the peripheral surface of the carotid artery was 5 mm in the blood flow direction.
One end of the polyurethane catheter prepared above and subjected to the surface treatment of the present invention prepared above was inserted by 3 cm, ligated from the outside of the blood vessel with a ligature, and the catheter was fixed in the carotid artery. Similarly, the central portion of the left carotid artery was incised, the other end of the catheter was inserted into the central portion, and similarly fixed with a ligature to form a carotid artery bypass. As a comparative example, a right carotid artery bypass was similarly formed using an untreated polyurethane catheter.

The carotid artery bypass was performed for 5 hours while maintaining the anesthesia with Frousen. Twenty days later, the catheters of the Examples and Comparative Examples were removed from the carotid artery of the dog, and immediately the inner and outer surfaces of both catheters were gently washed with a syringe in a saline solution of 2500 IU / 500 mL of heparin,
Blood was washed away. Thereafter, the degree of thrombus adhesion on the outer surface of both catheters was visually observed and comparatively evaluated.After that, the lumen of the catheter was cut open, and the degree of thrombus adhesion on the inner surfaces of both catheters was similarly observed and evaluated comparatively. .

(5) Evaluation Results The evaluation results of the vascular bypass catheters of the example and the comparative example were as follows.

[0019]

[Table 1]

[0020]

The present invention is intended to maintain the antithrombotic properties of a substrate for a long period of time by modifying the surface of the substrate with biodegradable fine particles provided with an antithrombotic substance and gradually decomposing the surface layer. . The antithrombotic substance immobilized on the surface of the biodegradable fine particles is gradually eliminated from the blood as the activity of the biodegradable fine particles is degraded as the activity decreases. For this reason, a new antithrombotic substance having high activity is supplied on the substrate, and excellent antithrombotic properties are maintained. The antithrombotic substance present inside the biodegradable microparticles is gradually released into the blood by the decomposition of the microparticles or the ingress of water, thereby maintaining the antithrombotic property of the base material.

[Brief description of the drawings]

FIG. 1 The vertical axis in the figure is the thickness of the fine particle layer, and the horizontal axis is time (days).
Is shown. It can be seen that the surface layer was slowly decomposed for 100 days or more.

Claims (2)

[Claims] 1. An antithrombotic material characterized by coating a substrate with a material in which an antithrombotic substance is immobilized via a hydrophilic substance on the surface of microparticles having biodegradability. 2. An antithrombotic material, characterized in that a material in which an antithrombotic substance is dispersed in biodegradable fine particles is coated on a substrate.