Preparation And Study Of MgF₂/PDA/S-HA Composite Coating On ZE21B Alloy

Biomedical magnesium alloy vascular stents have attracted much attention due to their excellent mechanical properties,biodegradability and biocompatibility,but their degradation behavior and biocompatibility still have a large space for improvement.In recent years,functional molecules such as polydopamine(PDA),hyaluronic acid(HA)and heparin have been widely studied in the field of surface modification of magnesium alloy stents,but their further application is limited by poor anticoagulant function,easy degradation by enzymes in human body and easy bleeding,respectively.Therefore,sulfonated hyaluronic acids(S-HA)with different sulfur content of2.06,3.69,7.10,8.98,and 9.71 were prepared by combining the functional structure of heparin(sulfonic group)with HA.Then,the polymers were characterized by X-ray photoelectron spectroscopy(XPS),Fourier transform infrared absorption spectroscopy(FTIR)and elemental analysis.It was found that the sulfur content of S-HA was positively correlated with the molar ratio of sulfonating agent to polymer.In addition,Vascular endothelial cell(VEC)proliferation test,VEC apoptosis test,VEC migration test,VEC morphological observation test,VEC nitric oxide(NO)release test,Macrophage(MA)adhesion test,MA polarized phenotype test and smooth muscle cell(SMC)regulation experiment were used to investigate the cardiovascular compatibility of the polymers.Relevant studies have shown that the increase of sulfonic acid groups can enhance the stability of S-HA,which is conducive to the polymer to play a better role in cell regulation.In this study,it was found that S-HA with high sulfur content can promote the proliferation,migration,adhesion and release of NO of VEC.Additionally,it is beneficial for SMC to maintain contractile phenotype or regulate the transition of SMC from synthetic phenotype to contractile phenotype.Moreever,this polymer could inhibit the adhesion/polarization of inflammatory MA and inhibit the inflammatory response.Furthermore,a magnesium fluoride/polydopamine/sulfonated hyaluronic acid(Mg F₂/PDA/S-HA)composite coating was successfully prepared by applying S-HA with sulfur content of 9.71wt%on the surface of ZE21B alloy in this study.After that,functional groups,elemental components,surface morphology,roughness,wettability,corrosion resistance,blood compatibility and cell compatibility of the composite coating was studied by FTIR,XPS,scanning electron microscopy(SEM)and X-ray energy spectrum(EDS)analysis technology,atomic force microscope(AFM)analysis technology,water contact angle measurement technique,electrochemical corrosion experiment,immersion corrosion experiment,platelet adhesion experiment,hemolysis rate test,VEC apoptosis test,MA polarized phenotype test and SMC regulation experiment.The experimental results show that the composite coating which has a unique network structure not only inherited the anticoagulant effect of sulfonic acid group(the surface platelet adhesion density was only 5.6%of that of the magnesium fluoride/polydopamine composite coating)and the excellent cell compatibility of S-HA with high sulfur content(support the normal growth of VEC,help SMC maintain contractile phenotype,and inhibit inflammatory response),but also had significant improvement effect on the corrosion resistance of ZE21B alloy(corrosion current density decreased by 96.7%).This means that the composite coating has great potential for application in the field of cardiovascular biomaterials.