Hydroxyapatite coating on magnesium with MgF2 interlayer for enhanced corrosion resistance and biocompatibility

Hydroxyapatite (HA) was coated onto pure magnesium (Mg) with an MgF2 interlayer in order to reduce the surface corrosion rate and enhance the biocompatibility. Both MgF2 and HA were successfully coated in sequence with good adhesion properties using the fluoride conversion coating and aerosol deposition techniques, respectively. In a simulated body fluid (SBF), the double layer coating remarkably enhanced the corrosion resistance of the coated Mg specimen. The in vitro cellular responses of the MC3T3-E1 pre-osteoblasts were examined using a cell proliferation assay and an alkaline phosphatase (ALP) assay, and these results demonstrated that the double coating layer also enhanced cell proliferation and differentiation levels. In the in vivo study, the HA/MgF2 coated Mg corroded less than the bare Mg and had a higher bone-to-implant contact (BIC) ratio in the cortical bone area of the rabbit femora 4 weeks after implantation. These in vitro and in vivo results suggested that the HA coated Mg with the MgF2 interlayer could be used as a potential candidate for biodegradable implant materials.