| With the development of society,people's life style is becoming more and more diversified.At the same time,bad living habits also affect people's health.According to statistics,the number of patients with coronary heart disease in our country shows a trend of gradual rise,has caused a greater impact on People's Daily life.Drug-eluting stent is one of the effective measures in the treatment of coronary heart disease.At present,many drug-eluting stents on the market only carry one drug,which cannot solve all the symptoms such as smooth muscle cell proliferation,inflammation and thrombosis caused by stent implantation.In addition,the drug-carrying coating on the drug-eluting stent has insufficient adhesion,and the problem of drug coating peeling is easy to occur in the process of use.Therefore,it is very important to develop new drug-eluting stents.316L stainless steel is widely used as medical implants due to its excellent corrosion resistance,mechanical properties and good biocompatibility.It is one of the main materials for coronary scaffolds.In this paper,a two-step anodic oxidation method was used to prepare the overlapping structure of "large pores with small pores" on the surface of 316 L stainless steel.Using the overlapping-pore structure,the surface layer of macropores is loaded with the degradable polymer drug coating PLGA/RAPA,which increases the bonding force between the drug coating and the substrate and is not easy to fall off.DXMS drugs were loaded into the bottom pores to achieve the effect of double-loading,so as to meet the different needs of drugs for stent implantation.At the same time,the blood compatibility,corrosion resistance,roughness,adhesion and wettability of the overlapping pores or drug-loaded sample were studied.The research results are as follows:1.In the preparation process of overlapping pores by two-step anodic oxidation method,the first step of anodic oxidation is: 0.3mol/L sodium dihydrogen phosphate solution is used as the electrolyte,the oxidation voltage is 30 V,the temperature is 0?,and the time is 20min;The second step of anodic oxidation: the electrolyte is ammonium fluoride/ethylene glycol organic electrolyte system,in which the concentration of ammonium fluoride is0.05-0.15mol/L,the oxidation voltage is 20-60 V,the temperature is 10-20?,and the time is10 min.Under this reaction condition,the overlapping pores prepared are relatively regular,in which the macropores are reticulated and the pore size is between 180-260 nm.The small pores in the macropores are honeycombed and the pore size is about 20-50 nm,and the pore length is up to 4.37?m.2.The overlapping-pore structure(oxide film)formed in situ after anodic oxidation has a high binding force with the stainless steel matrix,and its corrosion resistance is also significantly improved compared with the polished sample.Secondly,the porous oxide film can increase the adhesion of PLGA drug coating.Polished sample,overlapping-pore sample and overlapping-pore-PLGA drug composite coating sample are hydrophilic,and the surface roughness are small,which meet the requirements of blood compatibility.In the hemolysis test,the hemolysis rate of the overlapping-pore-PLGA drug composite coating sample was the lowest,followed by the overlapping-pore sample and the polished sample,which all meet the hemolysis rate requirements of biological materials.3.Among drug loading samples with different surface microstructure,the two drugs with overlapping-pore loading sample have the best sustained release performance,which can meet the different needs of drugs for stent implantation.Within 25 days of drug release,the increase of drug loading in DXMS had little effect on the total release rate of DXMS,while the release rate of RAPA was less,and the release rate showed an increasing trend.PLGA can significantly improve the sustained release effect of DXMS drugs,and the increase of PLGA/RAPA loading will reduce the release rate of DXMS drugs,while the release rate of RAPA is less,and the release rate has little change. |
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