Study On The Biocompatibility Of Layer-by-layer Selfassembly CA-RGD Coating On ZE21B Alloy

Magnesium alloy stent has been widely investigated because of its excellent biodegradability.However,excessively rapid degradation rate and poor biocompatibility seriously limited the clinical application of magnesium alloy stents.To further meet the clinical requirements,a fluoride conversion layer was first prepared on the surface of ZE21B alloy.Then three dopamine deposition times of 6 h,12 h and24 h were selected for parameter discussion,and the optimal parameters of 24 h was screened out by the quantification of amine group and electrochemical polarization curves for subsequent coating preparation.Finally,the multifunctional coatings with different layers were covalently immobilized on MgF₂-PDA layer by citric acid（CA）and Arginine-Glycine-Aspartic Acid（Arg-Gly-Asp,RGD peptide）via a layer-by-layer self-assembly method.The main contents of this thesis were summarized as follows:A serious of material characterizations were conducted by scanning electron microscopy（SEM）,atomic force microscope（AFM）,water contact angle and step profiler;Quantification of amine group,Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）were used to determine the content and composition of functional groups and elements during the preparation of self-assembled coatings;The corrosion resistance of the self-assembled coatings was comprehensively evaluated through electrochemical experiment,weight loss experiment and immersion experiment;The blood compatibility of the self-assembled coatings was evaluated through platelet adhesion experiment,hemolysis rate experiment and fibrinogen adhesion/denaturation experiment;The effects of self-assembled coatings on promoting endothelialization,anti-proliferation and anti-inflammation were systematically evaluated through cell culture experiments in vitro.The material characterization results indicated that the self-assembled coatings were successfully fixed on MgF₂-PDA layer,and all the PDA/（CA-RGD）samples displayed hydrophilic surfaces;The corrosion resistance of HF sample and PDA/（CA-RGD）₂sample was proved to be superior than other experimental groups by electrochemical experiment,weight loss experiment as well as immersion experiment.The blood experiments showed that the PDA/（CA-RGD）coatings effectively reduced hemolysis rate,platelet activation and fibrinogen adhesion,thereby improving the blood compatibility of ZE21B alloy.Taken together,PDA/（CA-RGD）₂ sample has the most significant effect;The in vitro cytocompatibility experiments indicated that the PDA/（CA-RGD）₂ sample not only displayed excellent performance in promoting surface endothelialization,but also provided sustained inhibition effects on anti-proliferation.Although the PDA/（CA-RGD）₁sample and PDA/（CA-RGD）₃sample also presented a certain effect on promoting endothelialization,the risk of in-stent restenosis caused by over-proliferation of SMCs was not reduced.In addition,the results of macrophages culture indicated that the PDA/（CA-RGD）₂ sample did have a certain inhibitory effect on inflammation.All in all,the PDA/（CA-RGD）₂ coating not only significantly improves the corrosion resistance,but also displays excellent anti-coagulation,endothelium promoting,anti-proliferation and anti-inflammatory effects.The coating also provides a new strategy for the surface modification of magnesium cardiovascular stents.