A polyphenol-induced hydroxyapatite coating modulates corrosion resistance and biocompatibility of magnesium alloys

In order to solve the problem of excessive degradation rate and insufficient biocom-patibility of magnesium-based bone implants,a polyphenol(EGCG)induced hydroxy-apatite(HA)coating was prepared on the surface of AZ31 alloy.The physical and chemical properties and corrosion resistance of the coating were analysed in depth,and its biocompatibility was preliminarily explored in vitro.The results showed that the polyphenol(EGCG)conversion coating constructed on the AZ31 could successfully induce the formation of HA by complexing the phenolic hydroxyl group with calcium ions.The electrochemical and long-term immersion experiments showed that the corrosion resistance of EGCG/HA composite coating was significantly improved.The self-corrosion current density,hydrogen evolution and the increase of pH value of AZ31-EGCG/HA were significantly lower than those of AZ31.On the basis of inhibiting the excessive corrosion of the substrate,the composite coating significantly improves the compatibility of pre-osteoblasts,supports the adhesion and spreading and effectively reduces the haemolysis rate to less than 5%.The preparation method of the coating is simple,low cost and suitable for complex shape surfaces,which can significantly improve the corrosion resistance and biocompatibility of the AZ31 substrate.It is expected to provide a solution for the surface modification of magnesium-based bone implants.