Preparation And Properties Of PDA/FA Coating On Mg-Zn-Y-Nd Alloy For Vascular Stent

Magnesium alloy vascular stent has been widely studied because of its excellent mechanical properties,good biocompatibility and degradability.However,its rapid degradation rate,poor blood compatibility and insufficient degree of endothelialization limit the development of its biomedical field.In order to improve the properties of magnesium alloys,loading bioactive molecules is a common modification method,and natural antioxidants have been explored and applied to the study of vascular stents because of their unique biomedical functions.In this paper,the bioactive molecules of three typical antioxidants,tannic acid(TA),gallic acid(GA)and ferulic acid(FA),were selected to prepare functional coatings on Mg-Zn-Y-Nd alloy by different processes.Firstly,the time of alkali heat treatment,3-aminopropyltriethoxysilane(APTES)treatment and dopamine dip coating were optimized.Through morphology,EDS energy spectrum and electrochemical test,the optimal time parameters were determined as 8 hours of alkali heat treatment,0.5 hours of APTES dip coating time and 24 hours of dopamine dip coating time.After that,the three antioxidant coatings were screened by element composition,electrochemistry,hydrophilicity and roughness tests,and finally the PDA/FA composite coating prepared by FA and polydopamine(PDA)was selected.The corrosion resistance of FA-1 h,FA-3 h and FA-6 h coatings was studied with different treatment time.The main research contents of this paper are as follows:The morphology of the sample was observed by scanning electron microscope(SEM),the three-dimensional structure and roughness of the sample were observed by atomic force microscope(AFM),the hydrophilicity of the sample was tested by water contact angle,and the element composition and functional groups of the coating were determined by energy dispersive spectroscopy(EDS),infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS).The antioxidant capacity of the samples was tested by 1,1-diphenyl-2-trinitrophenylhydrazine(DPPH)radical scavenging method.The corrosion resistance of the samples was tested by electrochemical test,weight loss test,immersion test and magnesium ion release test.The blood compatibility of the samples was tested by hemolysis rate,adhesion and denaturation of fibrin and platelet adhesion test.The cell compatibility of the samples was tested by endothelial cell culture experiment and smooth muscle cell culture experiment.SEM,AFM and other material characterization show that FA is successfully fixed on PDA coating,and PDA/FA coating has good uniformity,low roughness,good hydrophilicity and excellent oxidation resistance.A series of corrosion resistance experiments show that FA-3 h sample has good corrosion resistance and can slow down the corrosion of magnesium alloy for a long time.Blood experiments showed that FA-3 h had good blood compatibility,which could reduce the hemolysis rate,inhibit the degeneration of fibrinogen and inhibit the adhesion and activation of platelets.Cell experiments showed that FA-3 h sample had significant endothelialization promoting ability and could inhibit the adhesion and growth of smooth muscle cells.In conclusion,FA-3 h sample has relatively excellent comprehensive properties and has great potential in magnesium alloy vascular stents.By introducing FA,an antioxidant and traditional Chinese medicine extract,the corresponding properties of Mg-Zn-Y-Nd alloy are significantly improved,which provides a new scheme for the surface modification of magnesium alloy vascular scaffolds.