Preparation And Performance Study Of Calcium-Phosphorus Composite Coatings For Medical Magnesium Alloys

Magnesium and magnesium alloys have become a hot research topic in the field of bone injury repair as a new generation of biodegradable hard tissue repair implants with elastic modulus comparable to that of human bone,which can be completely degraded in vivo without avoiding secondary surgical removal.However,its excessively rapid corrosion rate in liquid environments and potential cytotoxicity have limited its further clinical application to a certain extent.At present,surface modification treatment can effectively reduce the degradation rate of magnesium alloy to a certain extent,and at the same time,the surface modification can give magnesium alloy certain biological properties,and a functional coating with good corrosion resistance and biocompatibility has great advantages in optimising the performance of magnesium alloy.In this paper,a calcium-phosphorus composite coating was prepared on the surface of AZ31 using a simple hydrothermal method and a conventional immersion method,using a commercial AZ31 magnesium alloy as the substrate material.The main studies and results of this thesis are:（1）By etching AZ31 with hydrochloric acid,a homogeneous network-like morphology was etched on the surface of AZ31,which provided more nucleation sites for the growth of HAp and improved the interfacial bonding strength of HAp,while（H⁺）HAp/CS composite coating was prepared by using chitosan（CS）with good biocompatibility as a sealing layer for the pores of HAp coating.Electrochemical experiments,hydrogen precipitation experiments and cytocompatibility assessment have shown that the composite coating can effectively reduce the degradation rate of magnesium alloy,has good corrosion resistance,and the low magnesium ion precipitation concentration during the cell culture process has less effect on cell growth,and can promote the attachment and proliferation of osteoblasts of BMSCs,showing excellent cytocompatibility.（2）The Mg Al LDH/HAp composite coating was prepared in situ on the AZ31surface by hydrothermal method,and the Mg Al LDH/HAp composite coating was prepared by cross-linking the free hydroxyl groups on the LDH surface with Ca²⁺,and the composite coating had a homogeneous rod-like structure,The composite coating has a special film structure due to the large surface area of the graphene oxide（GO）itself.The Mg Al LDH/HAp/GO composite coating exhibited good corrosion resistance in electrochemical tests,and in addition,the survival rate of osteoblasts from BMSCs was significantly better than that of AZ31,Mg Al LDH and Mg Al LDH/GO in cytotoxicity tests.HAp composite coating,indicating that the Mg Al LDH/HAp/GO composite coating was less cytotoxic.（3）Zn Al LDH/SA/HAp-CAT antibacterial coatings were prepared on AZ31surfaces by hydrothermal and conventional immersion methods.The Zn Al LDH/SA/HAp-CAT antimicrobial coating was found to have good anti-corrosion properties through electrochemical experiments,immersion experiments and hydrogen precipitation experiments.In vitro bacterial studies revealed that the composite coating exhibited some antibacterial properties against Staphylococcus aureus and Escherichia coli.In vitro biological studies have shown that the composite coating not only has good biocompatibility but also shows some osteodifferentiation properties for BMSCs cells.