JP4604177B2 - Antithrombotic polymer composition - Google Patents

Description

  The present invention relates to a polymer composition having antithrombogenicity and suitably used as a medical material.

  In recent years, synthetic polymer materials have been widely used for medical materials such as artificial organs and catheters. Typical examples of the medical polymer material include hydrophobic polymers such as polyester, polysulfone, polyvinyl chloride, polystyrene, silicone resin, polymethacrylic acid ester and fluorine-containing resin, polyvinyl alcohol, polyether urethane ( Hydrophilic polymers such as segmented polyurethane (SPU), poly (2-hydroxyethyl methacrylate) and polyacrylamide.

Of these, hydrophobic polymer materials are not satisfactory in terms of biocompatibility, and hydrophilic polymers are not satisfactory in terms of mechanical strength. While most of these conventional materials have been used mainly focusing on their physical and mechanical properties, it is known that SPU is relatively excellent in antithrombogenicity. Among them, BiomerR (Ethicon, trade name), CardiothaneR (Avco, trade name), etc. have been tried to be applied to an artificial heart, but have not yet achieved sufficient effects. (For example, see Non-Patent Documents 1 and 2)
E. Nylas, RCReinbach, JBCaulfield, NH Buckley, WGAusten; J. Biomed. Mater. Res. Symp., 3, 129 (1972), LPJoyce, MCDevries, WSHastings, DBOlsen, RKJarvik, WJKolff; Trans.ASAIO, 29,81 (1983)

  In these segmented polyurethanes, platelet adhesion is suppressed by a microphase separation structure between a rigid aromatic urethane bond site and a flexible polyether bond site, but the effect is not sufficient. In particular, hydrogen-bonded partial structures such as urethane bonds and urea bonds contribute to improving the rigidity of the molecular chain, but the strong interaction between polar groups in the main chain makes it possible to reduce the hydrophobic interaction. Molecular hydration is inhibited. Therefore, it has been reported that when blood proteins are adsorbed, protein denaturation is induced and platelet adhesion is promoted.

In the first place, in general, polar sites such as hydroxyl groups and amino groups induce complement activation (second pathway) at the time of blood contact, and also cause thrombus formation by promoting fibrin formation. Among other polyester polymers, PEO (polyethylene oxide) / PBT (polybutylene terephthalate) copolymer is known as a biocompatible polymer with excellent blood compatibility (see Patent Document 1), which is also highly hydrolyzed. And there are drawbacks in terms of chemical stability such as leakage of low molecular eluates and oligomers into the body, and this is a serious problem in practical use.
JP 60-238315 A

A material design that suppresses platelet adhesion and develops antithrombogenicity by making the polymer surface a hydrophilic / hydrophobic microdomain structure is known for HEMA (2-hydroxyethyl methacrylate) -styrene-HEMA block copolymer, etc. However, this is also expensive, and it is brittle and difficult to melt and wet.
C. Nojiri, T. Okano, D. Grainger, KD Park, S. Nakahama, K. Suzuki, SW Kim, Trans. ASAIO, 33, 596 (1987)

Recently, by adapting fluoroalkyl groups with low surface energy (high hydrophobicity) to hydrophobic domains with a microdomain structure, the phase separation state with hydrophilic domains with high surface energy is stabilized, making it more blood compatible Although attempts have been made to improve the processability, the problem of workability has not been solved. It was also shown that MPC (2-methacryloyloxyethyl phosphorylcholine) -BMA (butyl methacrylate) copolymer having a biomembrane-like surface structure is excellent in antithrombogenicity (Non-patent Document 4). There are problems with sex and price.
K. Ishihara, R. Aragaki, T. Ueda, A. Watanabe, N. Nakabayashi, J. Biomed. Mater. Res., 24, 1069 (1990)

  On the other hand, with the advancement of medical technology, the chance of contact between a living tissue or blood and a material has increased, and the biocompatibility of the material has become a big problem. In particular, the adsorption and denaturation of biological components such as proteins and blood cells on the surface of the material not only cause unacceptable adverse effects such as thrombus formation and inflammatory reaction on the living body side, but also lead to deterioration of the material. This is an important issue that must be solved fundamentally and urgently.

  In particular, members such as blood circuits used for extracorporeal circulation of blood and catheters inserted into blood vessels are indispensable for surgical medicine, and have greatly contributed to the progress of these technologies. While the mechanical properties of these materials have been greatly taken into consideration for the required properties as members, blood compatibility has not been improved at all, and blood coagulation is barely achieved mainly by the administration of anticoagulants such as heparin in the blood. The foreign body reaction was suppressed.

  However, it has recently been recognized that side effects such as liver damage such as abnormal lipid metabolism due to continuous long-term administration of heparin, prolonged bleeding time, or allergic reaction. From such a viewpoint, when using these blood contact medical devices, the amount of anticoagulant used is reduced or blood coagulation is not caused even if it is not used at all. Development has become highly desirable.

  Generally, soft polyvinyl chloride having excellent mechanical properties such as flexibility and pressure resistance is frequently used for these members. This soft polyvinyl chloride also has a problem in blood compatibility, and its improvement has been studied. Soft polyvinyl chloride contains a plasticizer such as dioctyl phthalate as an additive. For this reason, in the surface coating of an antithrombotic polymer using a solvent, leakage of the plasticizer into the solvent becomes a problem depending on the solvent used. Even if the surface can be successfully coated, the affinity with the antithrombotic polymer is low, and the polymer may be peeled off during use.

In the past, in order to solve this problem, it has been disclosed that a micron-sized alloy having excellent antithrombogenicity can be obtained by blending soft polyvinyl chloride and polyether ester (Patent Document 2). Has not solved the problem of leakage of the eluate in the body due to hydrolysis of the polyether ester. Also, blood compatibility itself is not excellent.
Japanese Patent Publication No. 2-35580

It has also been proposed to increase the adhesion of the antithrombotic polymer by using a polyvinyl alcohol copolymer as the antithrombotic polymer and grafting the vinyl alcohol-vinyl chloride copolymer onto the surface of the soft polyvinyl chloride. (Patent Document 3), at present, it is known that polyvinyl alcohol itself does not have satisfactory blood compatibility, and better surface immobilization of an antithrombotic polymer is desired. There have also been reports of chemically immobilizing physiologically active substances such as heparin with excellent anticoagulant properties on the surface, but there are problems with the complexity of the process and the sustainability of the effect due to chemical instability of the physiologically active molecule. It has not been solved and has not been put into practical use.
Japanese Patent No. 2568108

  Therefore, an object of the present invention is to provide a polymer composition that is practical in terms of cost, moldability, etc. and has good antithrombogenicity as a medical material, and a medical material using the polymer composition. To provide materials.

  The present inventors have developed a polymer composition excellent in blood compatibility (particularly antithrombogenicity). A polymer compound having an ethylene glycol unit is expected to be more or less antithrombogenic. It is well known that antithrombogenicity is improved by grafting polyethylene glycol to the surface of another polymer by plasma treatment or the like. In this case, a water-soluble brush structure is formed on the surface, and proteins, platelets, and cells are generated from the surface by repulsive interaction with foreign substances due to entropy elasticity. In addition, the polyethylene glycol itself constituting the brush is water-soluble and does not cause a hydrophobic interaction with the protein. This ideal method requires post-treatment of the surface, so that productivity is significantly low and is not industrially desirable.

  On the other hand, many attempts have been made to obtain a polymer material having excellent antithrombogenicity by introducing a hydrophilic unit such as ethylene glycol into the main chain or side chain of the polymer chain. It is not at a level that can respond to the request. This is because there is a fundamental contradiction described below. When a water-soluble unit is introduced as a random copolymer into a side chain or main chain, the hydrophilicity of the surface is improved, the hydrophobic interaction of proteins and the like is inhibited, and the antithrombogenicity is improved. However, on the other hand, the solubility of the polymer in water (blood) also increases at the same time, and in particular, there is an upper limit for the introduction of the water-soluble unit because the dissolution of low molecular weight components becomes a problem.

  We paid attention to the use of block copolymers as a means to solve this problem. That is, a block copolymer composed of a water-soluble block and a hydrophobic block is used. PS (polystyrene) -HEMA (2-hydroxyethyl methacrylate) is known as a method using a similar block copolymer, but HEMA is hydrophilic but not soluble in water, so it has sufficient function. I can not expect. In addition, it is necessary to use it as a composition mixed with another polymer in consideration of cost reduction and other mechanical properties.

  The material is molded in air, but HEMA has a high surface energy due to the presence of its hydroxyl group, and can only give a surface composition lower than the blend ratio. In other words, when medical devices are molded using these materials, HEMA is buried inside because it is molded in air (vacuum), and cannot be deposited on the surface, resulting in antithrombogenicity. I can't expect it. The trade-off between hydrophilicity and surface energy cannot be solved.

  The inventors of the present invention provide a polymer 2- [2- (2-methoxyethoxy) ethoxy] ethyl methacrylate (PME3MA) comprising a methacrylate having a 3 unit ethylene oxide chain in the side chain and a terminal of which is a methyl group. However, it was soluble in water, and a block copolymer with polystyrene was synthesized. The surface composition was analyzed by X-ray Photoelectron Spectroscopy (XPS) and Dynamic Secondary Ion Mass Spectrometry (DSIMS). . This is a surprising result, but is thought to be due to a decrease in surface energy due to precipitation on the surface of the side chain end.

  The present inventors have noted that the fact that a water-soluble block has a relatively low surface energy has a high potential for application as an antithrombogenic material. This is because when PS-PME3MA is blended with PS, it can be expected that PME3MA blocks are selectively deposited on the surface. When the surface comes into contact with water (blood), the water-soluble PME3MA swells and protrudes into the water, forming a water-soluble polymer brush structure. Antithrombogenicity is expected due to the same effect as a polymer brush by graft polymerization or the like. In other words, it was found that the contradiction can be solved by making the side chain of the water-soluble block amphiphilic.

  The advantage of the present invention is that this surface structure is spontaneously formed simply by mixing the block copolymer of the present invention. In other words, by adding a block copolymer called PS-PME3MA slightly to a general-purpose material called PS, the surface of the material can be made extremely anti-thrombogenic easily and inexpensively without significantly changing the properties of the material itself. It can be expected to be granted. Here, an example is shown in which PS is used as the hydrophobic block. However, the hydrophobic block simply serves to bind to the base material, and therefore any water-insoluble material can be used.

  It is possible to change the biocompatibility of the surface of various polymers used in medical materials such as PMMA (polymethylmethacrylate) by changing the type of hydrophobic block depending on the polymer type to be blended. Easy to think. Even if the same kind of polymer cannot be introduced as a hydrophobic block due to the synthesis method, it can be easily considered that a hydrophobic block having a small interaction parameter (close to the solubility parameter) can be substituted.

  The antithrombotic polymer composition of the present invention includes [A] a polymer block represented by the following general formula (1) and a binary block comprising a polymer block represented by the general formula (2) It contains a copolymer and [B] polystyrene-based polymer.

In the above formulas (1) and (2), m is an integer of 10 to 10000; n is an integer of 3 to 10; q is an integer of 100 to 10000; R1 is H or CH ₃ ; R2 is C _p H _{2p + 1} (p is an integer of 1 ≦ p ≦ n / 2); R3 represents H or a C1-C10 alkyl group. The substitution position of R3 may be any of ortho, meta, and para.

  In the above formula (1), when n is 2 or less, the block does not have water solubility near body temperature, and the antithrombogenicity is not sufficient. When n is 11 or more, purification and polymerization are not easy. If p is outside the condition of 1 ≦ p ≦ n / 2, sufficient solubility in water cannot be obtained. The degree of polymerization m is desirably 10 or more in order to have sufficient antithrombogenicity. The upper limit is limited by the polymerization method, and is usually 10,000 or less. If the block is 9 yuan or more, the polymerization step increases, which is not desirable.

The degree of polymerization of the polystyrene block represented by the above formula (2) is suitably from 100 to 10,000.
Preferred block copolymers [A] include binary or ternary block copolymers. Among them, a polymer block of 2- [2- (2-methoxyethoxy) ethoxy] ethyl methacrylate and a polystyrene block are included. A block copolymer containing is particularly preferred.

The polystyrene polymer [B] mixed with the block copolymer [A] and constituting the antithrombogenic polymer composition of the present invention is not particularly limited, and is a polystyrene homopolymer, styrene and other vinyl monomers. Any known random or block copolymer may be used.
Preferred examples of the styrene polymer [B] include a polystyrene homopolymer and a polyalphastyrene homopolymer.

In the antithrombotic polymer composition of the present invention, the blending ratio of the block copolymer [A] is preferably about 1 to 50% by weight, particularly about 2 to 20% by weight, based on the whole composition.
According to the present invention, by incorporating a small amount of a block copolymer [A] into a general-purpose polystyrene polymer [B], it has excellent antithrombogenicity, and is a medical material including artificial organs, catheters and the like. As a result, a very useful polymer composition can be obtained.
When these medical materials are produced by the antithrombogenic polymer composition of the present invention, the medical material is composed of another material in addition to the medical material comprising the polymer composition itself. It can also be constituted by a material provided with a coating film comprising the polymer composition of the present invention on the surface.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, the following specific examples do not limit this invention. In the following examples, “%” means “% by weight”.
Example 1
A block copolymer (PS-PME3MA) composed of PS and PME3MA [methacrylate derivative with n = 3, p = 1 in the above general formula (1)] and PS blended in various blend ratios (PS- PME3MA was blended in toluene = 0, 3, 8, 9, 17, 50, 100%) and spin-coated on a silicon substrate surface having a size of 10 × 10 mm ² and a thickness of 1.0 mm. This was heat-treated at 100 ° C. for 1 hour in a vacuum to obtain a substrate having a coating layer of a polymer composition on the surface.

(Protein adsorption experiment)
Each substrate obtained was immersed in 5 mL of a phosphate buffer solution containing 4.6 × 10 ² μg / mL human-derived albumin or 40 μg / mL human-derived fibrinogen at 37 ° C. for 2 hours, and then the phosphate buffer solution was used. Washed twice and dried. The adsorption ratio of albumin or fibrinogen to each substrate surface was relatively evaluated by examining the element ratio (N / C) of nitrogen to carbon on the substrate surface by X-ray photoelectron spectroscopy. Carbon is a main constituent element of PS-PME3MA and PS, and nitrogen is a constituent element of protein. The results are shown in FIG. 1 (N = 6, error bars are standard deviations).
It can be seen that any protein has the largest amount of adsorption on the PS surface (PS-PME3MA 0%). The amount of protein adsorbed decreased sharply with the increase in the PS-PME3MA ratio in the coating layer (PS-PME3MA ratio 8-17%), and was almost zero at 50% or more. From the above results, it was found that the polymer surface containing PS-PME3MA suppresses protein adsorption.

(Example 2)
PS-PME3MA and PS are dissolved in toluene at various blend ratios (PS-PME3MA blending amount = 0, 4, 17, 24, 100%), and are glass discs with a diameter of 18 mm and a thickness of 0.12 to 0.17 mm. The surface was spin coated. This was heat-treated at 100 ° C. for 1 hour in a vacuum to obtain a disk having a coating layer of a polymer composition on the surface.

(Cell adhesion experiment)
Mouse fibroblast-derived L929 cells were suspended in a MEM cell culture solution containing 5% horse serum so as to have a concentration of 1.2 × 10 ⁵ cells / mL. The prepared sample was set in a 12-well cell culture microplate, and 2 mL of the cell suspension was poured into each well. After culturing for 20 hours in an incubator maintained at 37 ° C. and 5% CO ₂ atmosphere, the culture solution was aspirated from each well, and the sample was washed twice with a phosphate buffer. Next, the cells adhering to the sample surface were peeled off using a mixed solution of 0.25% trypsin and 0.02% EDTA, and stained with 0.3% trypan blue. The number of stained cells was counted with a Tatai cell counter. The results are shown in FIG. 2 (N = 6, error bars are standard deviations).
It can be seen that the largest number of L929 cells adhere to the PS surface (PS-PME3MA 0%). The number of adherent cells rapidly decreased with an increase in the PS-PME3MA ratio in the coating layer (PS-PME3MA ratio 0 to 4%), and became almost zero at 4% or more. From the above results, it was found that the polymer surface containing PS-PME3MA suppresses not only protein but also cell adsorption.

(Platelet adhesion experiment)
Set the prepared sample in a cone-plate type rheometer and use CFSE [5- or 6- (N-Succinimidyloxycarbonyl) -3 ', 6'-0,0'-diacetylfluorescein; manufactured by Dojindo Laboratories, Inc.] Human platelet-rich plasma containing fluorescently-stained human-derived platelets at a concentration of 1.0 × 10 ⁸ cells / mL was injected between the cone and the sample. Immediately after the injection, the cone was rotated at a shear rate of 50 s ^{−1, and} the number of adherent platelets on the sample surface after 15 minutes was counted with an optical microscope attached to the rheometer. The results are shown in FIG. 3 (N ³ 3, error bars are standard deviations). It can be seen that the most platelets adhere to the PS surface (PS-PME3MA 0%). The number of adherent platelets decreased rapidly with an increase in the PS-PME3MA ratio in the coating layer (PS-PME3MA ratio 0 to 4%), and became almost zero at 4% or more.
From the above results, it was found that the polymer surface containing PS-PME3MA suppresses not only protein and cells but also platelet adsorption.

  As described above, the material comprising the polymer composition containing the block copolymer [A] and the polystyrene polymer [B] of the present invention is excellent in antithrombogenicity, etc., and is a blood storage container, an in-vivo sensor, an artificial heart. , And as a substrate for artificial blood vessels, etc.

For the substrate having the coating layer of the polymer composition on the surface obtained in Example 1, the PS of the PS-PME3MA block copolymer was determined by the nitrogen / carbon element ratio determined by XPS for protein (albumin / fibrinogen) adsorption. It is the figure plotted as a weight fraction in it. It is the figure which plotted the adsorption | suction number of L929 cell as a weight fraction in PS of PS-PME3MA block copolymer about the disk which has the coating layer by a polymer composition on the surface obtained in Example 2. FIG. It is the figure which plotted the adsorption number in the flow field of platelets as a weight fraction in PS of a PS-PME3MA block copolymer about the disk which has the coating layer by a polymer composition on the surface obtained in Example 2. .

Claims (4)

[A] A copolymer block represented by the following general formula (1) and a polymer block represented by the general formula (2) having a content of 1 to 50% by weight. An antithrombotic polymer composition comprising a polymer and [B] a polystyrene-based polymer:

(In the formula, m is an integer of 10 to 10000; n is an integer of 3 to 10; q is an integer of 100 to 10000; R1 is H or CH ₃ ; R2 is C _p H _{2p + 1} (p is 1 ≦ p ≦ n / 2 integer); R3 represents H or a C1-C10 alkyl group, respectively)   The antithrombogenic polymer composition according to claim 1, wherein the block copolymer [A] is a binary or ternary block copolymer.   The block copolymer [A] is a block copolymer containing a polymer block of 2- [2- (2-methoxyethoxy) ethoxy] ethyl methacrylate and a polystyrene block. The antithrombotic polymer composition according to 1. The medical material comprised by the antithrombogenic polymer composition in any one of Claims 1-3 .

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