Long-term corrosion resistance and fast mineralization behavior of micro-nano hydroxyapatite coated magnesium alloy in vitro

Abstract To improve the long-term corrosion resistance of biodegradable AZ31 magnesium alloy, the micro-nano structural hydroxyapatite (HA) coating was fabricated on AZ31 substrate by hydrothermal treatment. The compact and high crystallinity HA coating prepared at 120 °C had excellent electrochemical properties. Moreover, the cell viability experiment revealed that the micro-nano structure coating was conducive to the viability and proliferation of MC3T3-E1 osteoblasts. The immersion experiment in simulated body fluid (SBF) solution showed that the micro-nano structural HA coatings could quickly induce the production of HA mineralization, and then the mineralization evolved into a compact mineralized layer on the surface of coated sample, which provided a long-term protection for the specimen. Even after 147 days of immersion, the coated samples remained the relatively complete macroscopic shape, the corrosion rates were lower than 0.500 mm/y and the pH values of the SBF solution maintained in the range of 7.10–7.80, suggesting when these coated AZ31 magnesium alloys were used as degradable biomaterial implants, they could provide a long-term mechanical support during the healing of damaged bones.