Enhanced the corrosion resistance and biocompatibility of magnesium alloy by hydroxyapatite composite coating of AZ31/Ti/PDA/HA

A series of hydroxyapatite (HA) composite coatings of AZ31/HA, AZ31/PDA/HA, AZ31/Ti/HA, AZ31/Ti/PDA/HA were successfully fabricated combinedwith Ti ion implantation and Polydopamine (PDA). The SEM and EDS results showed that the AZ31/Ti/PDA/HA composite coating with a petal-like structure is more uniform and compact and the calcium-phosphorus ratio of AZ31/Ti/PDA/HA coating is 1.65, which is closer to the theoretical percentage of calcium-phosphorus in the hydroxyapatite of 1.67 compared to the other HA coatings. In addition, AZ31/Ti/PDA/HA coating exhibits best corrosion resistance, including the highest corrosion potential, lowest corrosion current and slowest amount of hydrogen evolution. The results of the MTT experiment showed that MC3T3-E1 cells presented a dendritic structure with no mitotic phase. The results of cell proliferation experiment showed that the cell proliferation rate of AZ31/PDA/HA, AZ31/Ti/HA, AZ31/Ti/PDA/HA group were higher than that of the negative control group except AZ31 substrate and AZ31/HA group. The 7-day cell proliferation rate of the AZ31/Ti/PDA/HA coating group was higher than those of the other groups. The AKP test showed that the ALP activity of the AZ31/Ti/PDA/HA coating group is strongest than other groups. Alizarin red staining results showed that the calcium nodules of the AZ31/Ti/PDA/HA coating group had the deepest staining and the highest density, which indicated that synergistic osteogenic ability of each component of composite coating was the best.