Degradability and biocompatibility of magnesium-MAO: The consistency and contradiction between in-vitro and in-vivo outcomes

Abstract Magnesium-based metals are promising for biomedical use for its biodegradation characteristic. However, its rapid degradation in physiological environment impedes its application. Oxides coating is a widely-used form of surface modification to improve the corrosion resistance of biomaterials. In this study, we systematically compared two oxides coatings, steam oxidation (SO) and micro-arc oxidation (MAO), in controlling degradation and improving the biocompatibility of pure magnesium in vitro and in vivo . The addition of both coatings was found to reduce the degradation rate of magnesium in vitro at the early stage, but the corrosion behavior became severe with longer immersion time in all the groups. Unfortunately, all the coated and uncoated materials were found undermining the adhesion and proliferation of MC3T3-E1 cells in vitro , even at the first day of culture. In terms of in-vivo circumstance, the Mg-MAO group showed satisfying biocompatibility compared with pure Mg and Mg-SO, as is evidenced by radiographic results and histological analysis. Little corrosion was found, and more newly formed bone was observed in the animal model. These data suggest that the characteristic of in-vivo circumstance have considerable impacts on the degradation and bone integration process.