RGDCPeptide-induced Biomimetic Calcium Phosphate Coating Formed On AZ31 Magnesium Alloy

Biodegradable magnesium alloys have attracted much more attention due to their excellent mechanical compatibility and biocompat ibility in biomedical applications. However, magnesium alloys have extremely high corrosion rates in chloride containing solutions including human body fluid and blood plasma, which have lim ited their applicat ion in the orthopaedic field.Calc ium phosphate is a major component of human bone matrix. It is reported that Ca-P coating has good biocompatibility, osteoconduction and osteoinduction. Biom imet ic is a novely method to prepare Ca-P coating, which has been successfully applied on to the s urface of mult iple materials. Some special funcitonal group on the surface with negative charge could absorb Ca2+ from simulated body fluid then induced Ca-P deposit. RGDC peptide are rich in carboxyl functional groups,which is a good metal-chelator. The study show that carboxyl functional groups can make a large number of positively charged Ca2+ ions in SBF adsorb on to the material’s surface. Subsequently, PO43- ions bound to Ca2+ ions formed stable calcium phosphate on to the metallic surface.In the present study, firstly arginine–glycine–aspartic acid–cysteine(RGDC) is immobilized onto the surface of AZ31 magnesium alloys through a covalent attachment to make the surface functionalizat ion. The elements of C,N,O,Si,S were detected by XPS after graf ting RGDC. RGDC was successfully grafted on to the surface of AZ31 by analyzing proportions of elements and chemical bonds. Then calcium-phosphate compounds(Ca-P) coating was prepared by RGDC peptide inducing mineralizat ion in 1.5 simulated body fluid(SBF). The structure and composition of coating were analyzed by SEM/EDS and XRD. The results indicated that a uniform and denser Ca-P coating which the main phase was HA had been deposited on the surface of AZ31 that treated by RGDC after immersed in simulated body fluid for 7 days.The corrosion behaviors of samples were investigated by potentiodynam ic polar izat ion curves and hydrogen evolution measurement. Murine fibroblast L-929 cells were harvested and cultured with coated and non-coated AZ31 samples to determine cytocompatibility. The results indicated that the Ca-P coating decreased the degradation of AZ31 alloy and cytotoxicity test indicated that the Ca-P coatings improved cytocompatibility of AZ31 alloy.