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.

Automated summary

By incorporating Ti ion implantation and Polydopamine into AZ31 coatings, a uniform and compact AZ31/Ti/PDA/HA composite coating with a petal-like structure was successfully fabricated, showing a calcium-phosphorus ratio closer to the theoretical value. This composite coating exhibited the best corrosion resistance and cell proliferation rate among all tested groups.