Biodegradability and antibacterial properties of MAO coatings formed on Mg-Sr-Ca alloys in an electrolyte containing Ag doped hydroxyapatite

Magnesium-based alloys are promising materials as next generation biodegradable implants, however low corrosion resistance and inadequate mechanical properties are limiting their application as a biodegradable implant material. In this study, Mg-Sr-Ca ternary alloys were prepared in a vacuum/atmosphere controlled furnace and coated by microarc oxidation (MAO) process for 5 min to decrease the degradation rate and enhance the biocompatibility. Moreover, Ag doped Hydroxyapatite nano powder (Ag-HA) was also added to alkaline MAO solution by amount of 1 and 10 g/l to improve the antibacterial properties while enhancing their bioactivity in a one single process. XRD, SEM-EDS, FTIR spectroscopy, simulated body fluid (SBF) immersion and antibacterial tests were employed for the characterization of the coated alloys. The results showed that, the addition of more Ag-HA increased the HA formation both before and after SBF immersion test and enhanced their antibacterial properties. However, Ag-HA addition decreased the corrosion resistance of the coated alloys in SBF compared to Ag-HA free coating. The results indicated that the present Ag-HA nano powder added MAO coating is a good combination to enhance the corrosion resistance, bioactivity and the antibacterial properties of Mg based biodegradable alloys.