Hydroxyapatite coating promotes stable physicochemical properties of pure magnesium in a longitudinal degradation study

Magnesium is attractive for orthopedic implants because of its similar mechanical properties to those of bone but often degrades too rapidly. Coatings such as hydroxyapatite (HA), the mineral component of bone, are useful for modulating degradation, thereby enhancing osseointegration and biocompatibility. The goal of this study was to longitudinally evaluate the effects of solution-deposited HA coating on magnesium degradation. We hypothesized the HA coating would be stable, slowing the degradation of pure magnesium. Analyses of mass; solution pH; magnesium in solution; surface morphology, chemistry, and roughness; and cytotoxicity were performed through 30 days. Despite morphological changes in the HA coating beginning at day 20, the mass, elemental composition, and surface roughness of the HA-coated group were unchanged through 30 days, demonstrating the stability of the coating and its ability to mitigate degradation of the underlying magnesium. This work provides longitudinal insight into the biodegradation of HA-coated magnesium for orthopedic implants. Graphical Abstract