WO2005097224A1

WO2005097224A1 - Polymer-coated stent

Info

Publication number: WO2005097224A1
Application number: PCT/JP2005/006063
Authority: WO
Inventors: Ikuo Omura; Shuzou Yamashita; Kouji Mori
Original assignee: Japan Stent Technology Co., Ltd.
Priority date: 2004-04-08
Filing date: 2005-03-30
Publication date: 2005-10-20
Also published as: JP2007236399A

Abstract

Disclosed is a polymer-coated stent wherein adhesion between a polymer coating and a metal as the base thereof is improved. After pretreating the base metal with a specific primer having an adhesion-enhancing effect, namely a primer containing an organic compound having a plurality of acidic hydroxyl groups and at least one functional group in a molecule, a hydrophobic and flexible polymer coating is formed over the base metal.

Description

Specification

Polymer-coated stent

Technical field

[0001] The present invention relates to a polymer one-coated stent having a polymer film firmly adhered to the surface of a metal stent and exhibiting excellent durability in which the polymer film does not peel off in a biological environment. About.

Background art

Description of the Related Art [0002] A stent is an annular medical device that is placed at a site in a living body such as a blood vessel, a trachea, a bile duct, etc., where the stenosis is obstructed or obstructed in order to secure a necessary lumen region. Tool. The stent is used to contract the tube diameter, insert it into the body by reducing it, expand it at a stenosis or the like, increase the tube diameter, and expand and hold the lumen. For example, in recent years, for the purpose of reconstruction of a stenotic blood vessel, percutaneous transluminal coronary angioplasty (1 ^ 10 1 & 5) (hereinafter referred to as? 1 ^ 8) has been proposed. Treatment is performed by dilatation with a 1 ^ 8 balloon catheter and placement of a metal stent. This stent is intended to prevent or suppress restenosis by sending a contrast agent to a balloon attached to a catheter and placing it in a blood vessel formed by expansion and expansion. In this way, stent placement is a technique that was performed with the expectation of suppressing restenosis in the angioplasty due to balloon dilatation alone.In fact, the earlier the prediction, the lower the restenosis rate It is the present situation that we can get. This is mainly due to neointimal hyperplasia due to migration and proliferation of smooth muscle cells associated with stent placement, and thrombosis due to damage to the arterial wall. Therefore, attempts have been made to block or suppress these side effects by covering the surface of the metal stent with a polymer coating holding a therapeutic agent (see, for example, Patent Document 1). Since the adhesion to the material deteriorates rapidly in the living body, there is a problem that the metal surface is easily peeled off by the metal surface.

Patent Document 1: JP-A-8-33718

Disclosure of the invention Problems the invention is trying to solve

[0003] Accordingly, an object of the present invention is to provide a polymer-coated stent having improved durability by suppressing deterioration of adhesion between a polymer film and a base metal in an in vivo environment.

[0004] Another object of the present invention is to provide a polymer-coated stent having both a drug-eluting property and a bonding durability of a polymer film to a metal.

Means for solving the problem

[0005] The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the surface of a metal stent was coated with a specific primer by force, and after being pressed, a polymer film was coated to form a polymer. The inventor has found that the coating adheres firmly to the metallic stent and that the adhesive durability in an in-vivo environment is significantly improved. The inventors have further studied and completed the present invention.

That is, according to the present invention, a specific primer is coated on the surface of a metal stent, and thereafter, a stent coated with a polymer film and a polymer film containing a therapeutic agent are further coated on the stent. Provide a stent.

[0007] As the metal which is the material of the stent, those having high corrosion resistance and high elasticity are preferable, and stainless steel, tantalum, nickel titanium alloy (including -tinol) and cobalt alloy (cobalt chromium) are preferable examples. Including a nickel alloy). The ability to coat these stents with a specific primer on these metal-processed stents In order to maximize the effectiveness of the primer, it is necessary to clean the metal surface. As the Tally-Jung method, a method used industrially is preferably used. That is, water washing, steam washing, solvent washing, mechanical polishing, chemical polishing, plasma washing, and ultraviolet (UV) Z ozone washing.

[0008] The specific primer used in the present invention includes an organic compound having a plurality of acidic hydroxyl groups and at least one functional group in a molecule (hereinafter, referred to as an acidic hydroxyl group-containing compound). It is one to which additives described later such as a volatile organic solvent are added. Examples of the acidic hydroxyl group of the acidic hydroxyl group-containing compound include hydroxyl groups of carboxylic acid, phosphoric acid monoester, phosphoric acid diester, phosphonic acid, phosphonic acid monoester, and phenol. As the functional group, a polymerizable group such as a (meth) atalyloyl group and a vinyl group, an amino group Amide group, epoxy group, isocyanate group, acid chloride group, acid anhydride group, hydroxyl group, mercapto group, azide group, trialkoxysilyl group and the like. The carbon number of the acidic hydroxyl group-containing compound in which a plurality of acidic hydroxyl groups and at least one functional group are bonded is preferably from 3 to 500, more preferably from 2 to 10,000. The acidic hydroxyl groups chemisorb to the metal surface of the stent, while the functional groups result in chemical bond formation between the components of the primer or with Z and the polymer coating deposited on the primer.

[0009] Above all, a pramer containing an acidic hydroxyl group-containing compound having a plurality of acidic hydroxyl groups bonded to a carboxyl group or Z and a phosphorus atom strongly adheres to various metals, particularly base metals, and has high adhesion durability in a biological environment. . In particular, when two acidic hydroxyl groups are bonded to the same phosphorus atom, that is, a monoester of phosphoric acid, phosphonic acid, or a hydroxyl group of two carboxyl groups substituted at the ortho position of the benzene ring, adhesion durability is high. Is significantly improved. Specific examples of suitable acidic hydroxyl group-containing compounds include 4-methacryloyloxyschiltrimellitic acid, 11-methacryloyloxy-1,1-undecanedicarboxylic acid, arylphosphonic acid, and 10-methacryloyloxydecyl diamine. Examples thereof include polymerizable monomers such as hydrogen phosphate, 10-aminodecylphosphonic acid, 11-hydroxy-1,1,1-decanedicarboxylic acid, and glycidyl trimellitic acid. In addition to the acidic hydroxyl group-containing conjugate, which is the main component, additives such as monomers, prepolymers, polymers, coupling agents, cross-linking agents, volatile solvents, surfactants, and polymerization initiators are used as necessary. It is blended. The amount of the acidic hydroxyl group-containing conjugate in the primer is 0.01 to: LOO weight%, preferably 0.1 to: LOO weight%.

[0010] The coating of the primer onto the metal stent is performed by a method such as dipping, spin coating, spraying and the like. The thickness of the coated primer is preferably between 0.001 and 1 μm. Therefore, it is necessary to select the composition of the primer and the coating method so that the coating layer is uniform and thin. For example, after coating with a primer, the excess primer can be washed with a solvent and then flown to leave only the acidic hydroxyl group-containing compound chemically adsorbed on the metal surface. If the primer contains a solvent, drying is required. When the primer is polymerizable, it can be polymerized and cured by a method such as heating, UV irradiation, or electron beam irradiation. [0011] The polymer to be coated on the primer layer is selected according to the purpose of the polymer film. If the polymer coating is expected to degrade and disappear over time when the stent is placed in a living body, a biodegradable polymer can be coated, but the polymer is stable in the living body and For ordinary applications that require no exposure of the stent metal surface due to degradation and degradation, a polymer with high biostability and biocompatibility (hereinafter referred to as biostable polymer) should be selected. Polymer coatings

From the viewpoint of in vivo durability of Z-metal adhesion (including the primer layer), it is desirable that the polymer has low water absorption, that is, hydrophobic. The polymer film needs to have a certain degree of flexibility because it needs to flexibly follow the polymer film without cracking during expansion and deformation of the stent. That is, the polymer suitable for the present invention is a biocompatible polymer having biostability, hydrophobicity and flexibility. Specific examples of such polymers include fluorosilicone-based resin, silicone-based resin, polyester-based resin, polyamide-based resin, polyurethane-based resin, polyethylene, (meth) atalylate-based polymer, and poly (ethylene butyl). Alcohol), homo- or copolymers of 2-methacryloyloxydecyl phosphorylcholine, and (2-hydroxyethyl methacrylate) styrene block copolymer.

[0012] A method of forming a polymer film on the primer includes a method of diluting a polymer with a solvent and coating the surface of the stent, and then evaporating the solvent to form a film (method A); The method is roughly divided into two methods: coating the monomer surface on the stent surface, and then polymerizing or Z-curing after crosslinking and curing by crosslinking (method B). Method A is applied to the formation of a film of a linear polymer that can be dissolved in a solvent, for example, a polybutyl methacrylate or a poly (ethylene vinyl alcohol) copolymer. The polymer solution can be coated by dipping, spin coating, or spraying, and after coating, the solvent is removed by forced drying (heating and decompression). Method B applies to prepolymers or Z and monomers in which the polymerization or Z and cross-linking reactions proceed in the Balta state. Specific examples thereof include prepolymers of epoxy resin, urethane resin, silicone resin, (meth) acrylate resin, and Z and monomers. In method B, a solvent, a polymer, a filler, and a polymerization initiator are added as necessary. If a solvent is added, before polymerization or cross-linking In addition, it is necessary to volatilize and remove the solvent. Polymerization Z cross-linking is performed by an intermolecular cross-linking reaction of prepolymers in epoxy resins, urethane resins, and silicone resins. On the other hand, in the case of (meth) acrylate resins, the polymerization is carried out by radical polymerization of monomers. The polymerization reaction is started and progressed by activating means such as heating of the coating layer of the monomer, irradiation of visible light to UV, and irradiation of electron beam. Since the radical polymerization reaction is hindered by oxygen in the air, the polymerization is preferably performed in an atmosphere of an inert gas such as nitrogen or argon or in a vacuum. The thickness of the polymer coating is usually 0.1 to 200 111, preferably 0.1 to 50 m, and the desired coating thickness can be achieved by repeating coating from 1 to: LOO times.

Furthermore, in the present invention, drug elution can be imparted to the polymer film as required. When imparting drug elution properties, a biodegradable or hydrophilic polymer film that adheres to the biostable polymer film is formed on the biostable polymer film, and the drug is incorporated in the film. Specific examples of the biodegradable polymer include polycaprolactone, poly L-lactic acid, poly DL lactic acid, polyglycolide, polylactide, glycolide lactide copolymer, polyether, polyorthoester, polyiminocarbonate, aliphatic polycarbonate, Examples thereof include polyamide and polyphosphazene. On the other hand, specific examples of the hydrophilic polymer include polyethylene oxide, sulfonidopolyethylene oxide, poly (2-hydroxyethyl methacrylate), polyacrylamide, polyvinylpyrrolidone, and polyvinyl alcohol. It is of course possible to apply these polymer coatings (hereinafter referred to as biodegradable or hydrophilic polymer coatings) directly on the underlying biostable polymer coating, but if the adhesion of both coatings is poor. In order to improve the adhesion, it is necessary to apply a surface treatment to the biostable polymer film prior to coating to activate the film. Examples of the surface treatment include chemical treatment with an oxidizing agent or fluorine gas, surface graft polymerization, plasma discharge treatment, corona discharge treatment, UVZ ozone treatment, and electron beam irradiation. The biodegradable polymer is dissolved in a volatile solvent to form a solution, which is coated on an untreated or surface-treated biostable polymer film surface, and the solvent is removed by means such as reduced pressure, air blowing, and heating. Examples of the volatile solvent include tetrahydrofuran, methylene chloride, chloroform, acetonitrile, methyl ethyl ketone, methanol, dimethyl sulfoxide, N, N-dimethylformamide, water, and mixtures thereof. I can make it.

[0014] Drugs to be eluted are antiplatelet agents, anticoagulants, thrombolytic agents, antifibrin, antithrombin, immunosuppressants, antiproliferative agents, anti-inflammatory agents, pile cancer agents, antioxidants, anti-metabolites , Anti-mitotic agents, hyperplasia inhibitors, smooth muscle cell inhibitors, antibiotics, growth factors, growth factor inhibitors, cell adhesion inhibitors, cell adhesion promoters and healthy neointimal tissue formation promoters, etc. is there. Also, genes, plasmids, decoys, antisenses and the like having a therapeutic effect can be incorporated in the polymer film and eluted in the same manner as the above-mentioned drugs. The simplest way to elute the drug from the biodegradable or hydrophilic polymer coating is to disperse the drug in the polymer at a molecular level to a micron size. In this method, a solution or dispersion obtained by dissolving or dispersing a drug as fine particles (even microcapsules) in the polymer solution is coated on a biostable polymer film. Coating is performed by a method such as dipping, spin coating, or spraying. By forcibly removing the solvent after coating, the polymer film containing the drug can be formed. Coating is repeated from 1 to as necessary: LOO times, and the coating thickness is controlled to 0.1 to 200 μm.

[0015] The rate of elution of a drug from a stent in a living body depends on the rate of degradation of a biodegradable or hydrophilic polymer and the rate of diffusion of a therapeutic agent within the polymer that has swollen by water. If the drug disperses too quickly in the polymer despite the slow rate of degradation of the polymer, and almost all of the drug elutes in a short period of time, the drug molecules will be adsorbed to the polymer and the diffusion will be delayed. It is necessary to modify the polymer, and the chemical modification performed for this purpose is specifically the introduction of a functional group such as a hydroxyl group, a carboxyl group, a sulfonic acid group, or an amino group. The interaction of the drug molecule functional groups with these functional groups slows the diffusion of the drug molecule and provides sustained release.

The invention's effect

[0016] The polymer-coated stent of the present invention has a polymer coating having excellent adhesion and durability formed on the surface of the metal stent, which is a weak point of the conventional polymer-coated metal stent, that is, the coating that occurs after implantation in a living body. Peeling can be prevented. As a result, the reocclusion rate after placement of an intravascular stent is reduced, and the addition of drug elution prevents thrombus and intimal hyperplasia. And the reocclusion rate is further reduced.

Brief Description of Drawings

FIG. 1 shows a stent according to an embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment capable of maximizing the effects of the present invention is as follows. That is, the surface of the metal stent to be coated with the polymer is washed with distilled water and then with a chlorine-based organic solvent such as trichloroethane to remove dirt, and then subjected to plasma cleaning to obtain a clean metal surface. Of methyl methacrylate click Relay preparative solution (a suitable amount of ultraviolet polymerization initiator containing a 0.5 to 5 wt ^_0/0 of the monomer having a-phosphate monoester group such as 10-methacryloyloxy Ruo carboxymethyl decyl = dihydrogen = phosphate on the surface Immersion for at least 1 minute, and then remove the solvent completely. Then, a coating solution obtained by dissolving 1 to 20% by weight of polyalkyl methacrylate and an appropriate amount of an ultraviolet polymerization initiator in methyl methacrylate (MMA) is applied to the surface of the primer-treated stent, and MMA is placed in a nitrogen atmosphere. Removed at room temperature to form a polymer film. Then, irradiate UV for about 10 minutes to completely cure the coating. Furthermore, a polylactic acid Z methylene chloride solution (polymer concentration: 1 to 20% by weight) in which an appropriate amount of fine powder of a drug such as henolin is dispersed is applied, and the methylene chloride is evaporated under reduced pressure at room temperature to produce biodegradation. Generate a functional polymer film.

[0019] The polymer-coated stent manufactured by the above-described steps is capable of preventing the polymer coating from peeling off from the metal surface even when the stent is left in an in-vivo environment for a long period of time. The sustained release of the drug clearly prevents restenosis of the lumen. In this specification, a force disclosed mainly in an intravascular stent as an example of the present invention is not limited to an intravascular stent. The present invention is not limited to an intravascular stent, and is used for a lumen such as trachea, bile duct, and intestinal tract. Is also included.

Example

Hereinafter, the ability to specifically explain the present invention by way of examples The present invention is not construed as being limited by the following examples.

FIG. 1 shows a stent 2 of an embodiment. In the stent 2, around the core wire 4 of Co—Cr alloy, etc.

Then, a primer layer 4 and a polymer layer 6 having a predetermined thickness are provided. The polymer layer 6, for example, The lower layer of the stable polymer is coated with the upper layer of a biodegradable or hydrophilic polymer.

[Example 1]

Completely immersed in Cr alloy stent (surface cleaning already only by the solvent) the unexpanded state - 10-methacryloyloxy Ruo carboxymethyl decyl = dihydrogen = phosphate The prototype acetone solution containing 1 wt ^_0/0 Co And left at room temperature for 1 hour. One hour later, it was taken out of the acetone solution and air-dried for 30 minutes to complete the primer treatment. Then, roughly 5 parts by weight of polybutyl methacrylate, 0.1 part by weight of ethylene glycol dimethacrylate, and 0.1 part by weight of 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TMDPO ) Was dissolved in 100 parts by weight of methyl methacrylate (MMA). The primed stent was immersed in the polymer coating solution prepared for 5 seconds, immediately pulled up from the solution, and lightly drained. After that, MMA was volatilized by standing still in a nitrogen stream at 50 ° C for 30 minutes under light shielding. The stent was placed in a sealed container made of quartz glass, the air in the container was replaced with nitrogen gas, and light from a metal halide lamp (200 W) was applied for 5 minutes at a short distance. The above-described polymer coating operation was repeated three times. In the third time, after irradiation with light, the stent was allowed to stand in a closed container for 6 hours. After removing the stent from the container and inserting a balloon into it and expanding it, the state of the polymer film on the stent surface was observed with a stereoscopic microscope (magnification: X100), and it was confirmed that the film had no defects such as cracks or peeling. confirmed. After the observation, the stent was immersed in a pH 7.4 phosphate buffer solution at 37 ° C and stored for 4 months. After the storage was completed, the stent was dried and observed with a stereoscopic microscope (magnification: X100). As a result, no cracks or delamination defects of the coating were observed.

[Comparative Example 1]

In Example 1, a polymer coating was formed on the stent surface under the same conditions except that the primer treatment was omitted. Next, the stent was expanded with a balloon, and the state of the polymer coating on the stent surface was observed with a stereoscopic microscope (magnification: X100). As a result, defects in which the coating was partially peeled off from the base metal were observed. After observation, the stent was immersed in a pH 7.4-phosphate buffer solution at 37 ° C and stored for 4 months. After the storage was completed, the stent was dried and observed with a stereoscopic microscope. As a result, many portions where the coating peeled off from the base metal were observed.

[Example 2] On the surface of the stent on which a coating mainly composed of polybutyl methacrylate was formed according to the method of Example 1, a hydrophilic polymer coating containing sarpodalelate hydrochloride was laminated according to the method described below. 30 wt% of glycerol monomethacrylate Tari rate, 4 wt% of glycerol dimethacrylate Tatari rate, 20 weight ^_0/0 hydrochloric acid Sarupodarerato were formulated a photopolymerizable coating solution consisting of 1% by weight of TMDPO and 45 wt% MMA . A stent having a coating of polybutyl methacrylate was immersed in the liquid for 5 seconds in an unexpanded state, and then pulled up from the liquid to drain off excess liquid. Next, the stain to which the coating solution was adhered was placed in a sealed container made of quartz glass, and the air in the container was replaced with nitrogen gas. Then, light from a metal halide lamp (200 W) was applied for 5 minutes at a short distance. The above coating was repeated again. Thereafter, the stent was allowed to stand in a closed container for 6 hours, taken out, and expanded by inserting a balloon into the stent. The state of the polymer coating of the expanded stent was observed with a stereoscopic microscope (magnification: X100). Defects such as cracks and peeling were not observed. After the observation, the stent was immersed in a pH 7.4-phosphate buffer at 37 ° C and stored for 4 months. After the storage was completed, the stent was dried and observed with a stereoscopic microscope, but no exposure of the base metal due to deterioration of the coating was observed.

(Example 3)

A biodegradable polymer film containing sarpodalelate hydrochloride was laminated on the surface of the stent on which a film containing polybutyl methacrylate as a main component was formed according to the method of Example 1 according to the method described below. 6 percent by weight of poly L-lactic acid and 4 wt% of hydrochloric acid Sarupogu Rerato and 90 weight ^_0/0 of KurohohorumukaゝRanaru coating solution was formulated. A stent having a polybutyl methacrylate film was immersed in the solution for 5 seconds in an unexpanded state, and then pulled up from the solution to drain off the excess solution. The port form was evaporated in a stream of nitrogen at 50 ° C. and the coating was repeated again. Next, a balloon was inserted into the stent to expand it. The state of the polymer coating of the expanded stent was observed with a stereoscopic microscope (magnification: X100). Defects such as cracks and peeling were not observed. After observation, the stain was immersed in PH7.4-phosphate buffer at 37 ° C and stored for 4 months. After the storage was completed, the stent was dried and examined with a stereoscopic microscope. No exposure of the base metal due to deterioration of the coating was observed. [Example 4]

4-methacryloyloxy Ruo key shell tilt trimellitic acid 1 wt%, poly E chill meth Tari rates 3 weight ^_0/0, the prototype benzo I peroxide in E chill meth cycle rate solution containing 0.1 wt ^_0/0 A stainless steel (SUS 316L) stent (having a surface sagged with a solvent) was completely immersed in an unexpanded state, and allowed to stand at room temperature for 1 hour. After 1 hour, the stain was taken out of the solution and air-dried for 30 minutes to complete the primer treatment. Next, the primed stent is immersed for 5 seconds in N, N-dimethylformamide (DMF) solution in which 4% by weight of polyester-type thermoplastic urethane (Bionate 80A) is dissolved, and immediately pulled out of the solution and lightly Drained. The stent was transferred to a closed vessel capable of reducing pressure, dried under reduced pressure at room temperature for 1 hour, then heated to 70 ° C. while maintaining reduced pressure, and heat-treated for 6 hours. After the heat treatment, the stent was taken out of the container, and a balloon was inserted into the stent and expanded. The state of the polymer coating on the expanded stent surface was observed with a stereoscopic microscope (magnification: X100), and it was confirmed that the coating had no defects such as cracks or peeling. After the observation, the stent was immersed in 37 ° C pH 7.4-phosphate buffer and stored for 4 months. After the storage was completed, the stent was dried and observed with a stereoscopic microscope (magnification: X100). As a result, no cracks or peeling defects were found in the coating.

Example 5

A prototype Co—Cr alloy stent (surface cleaned with a solvent) was completely immersed in a 0.5 wt% aqueous solution of arylphosphonic acid in an unexpanded state, and allowed to stand at room temperature for 1 hour. One hour later, the stent was removed from the aqueous solution and air-dried for 30 minutes to complete the primer treatment. Next, a silicone elastomer solution prepared by dispersing a two-part silicone elastomer (MED-2111) containing 89 g of hexane with 10 g of the main agent and a hardening agent lg was prepared, and the solution was hand-sprayed. The stent was sprayed uniformly. The stent was then heat cured in an oven at 60 ° C. for 24 hours to form a polymer coating. A balloon was inserted into the stent where the coating was completed, and the stent was expanded. The state of the polymer coating on the expanded stent surface was observed with a stereoscopic microscope (magnification: X100), and it was confirmed that the coating had no defects such as cracks and peeling. After the observation, the stent was immersed in 37 ° C PH7.4-phosphate buffer and stored for 4 months. After 4 months, the stent was dried and observed with a stereoscopic microscope (magnification: X100). No peeling defects were observed.

[Comparative Example 2]

In Example 1, a polymer coating was formed on the stent surface under the same conditions except that γ-methacryloxypropyltrimethoxysilane was used instead of 10-methacryloyloxydecyl dihydrogen phosphate. Was formed. Next, the stent was expanded with a balloon, and the state of the polymer film on the stent surface was observed with a stereoscopic microscope (magnification: X100). As a result, defects in which the film partially exfoliated the base metal force were observed. After the observation, the stent was immersed in a pH 7.4-phosphate buffer at 37 ° C and stored for 4 months. After the storage was completed, the stent was dried and observed with a stereoscopic microscope. As a result, many portions where the coating was peeled off from the base metal were observed.

[Comparative Example 3]

In Example 1, a polymer film was formed on the stent surface under the same conditions except that methacrylic acid was used instead of 10-methacryloyloxydecyl dihydrogen phosphate. Next, the stent was expanded with a balloon, and the state of the polymer film on the stent surface was observed with a stereoscopic microscope (magnification: X100). As a result, a defect in which the film was partially peeled off from the base metal was observed. After observation, the stent was immersed in a pH 7.4-phosphate buffer at 37 ° C and stored for 4 months. After the storage was completed, the stent was dried and observed with a stereoscopic microscope. As a result, a large number of portions where the coating was peeled off from the base metal were recognized.

Claims

The scope of the claims

[1] The polymer coating has a structure in which it is bonded to the surface of a metal stent via a primer layer containing an organic compound having a plurality of acidic hydroxyl groups and at least one functional group in a molecule. Polymer-coated stent.

[2] The stent according to claim 1, wherein two acidic hydroxyl groups are bonded to the same phosphorus atom.

[3] The stent according to claim 1, wherein the two hydroxyl groups are hydroxyl groups of two carboxyl groups substituted at an ortho position of a benzene ring.

4. The stent according to claim 1, wherein the polymer coating has a lower layer having a biostable polymer and an upper layer made of a biodegradable or hydrophilic polymer containing a drug.