Micro-arc oxidation (MAO) synthesized MgAl2O4 spinel-integrated coatings on Mg alloys: multidimensional exploration of biodegradation, biocompatibility, and osseointegration

The application of micro-arc oxidation (MAO) synthesized magnesium aluminate (MgAl 2 O 4 ) spinel-integrated coatings on Mg alloys has great potential for orthopedic implantats, because such a coating improves biodegradation resistance, which is an important limitation for the clinical applications of Mg alloys. However, to date, limited results are available for the biological response, and furthermore research is needed to understand the mechanisms that influence biocompatibility and osseointegration. This work successfully prepared a MAO coating containing MgAl 2 O 4 spinel on the surface of the Mg alloy AZ31 through optimizing a NaAlO 2 concentration of 6 g/L in the electrolyte, and studied the construction, biodegradation, biocompatibility, and osseointegration. The MAO coating containing MgAl 2 O 4 spinel (i) contained 94 % MgAl 2 O 4 , had a porosity of 1.2 % and a thickness of ∼26 μm; (ii) provided long-term stable protection in Hank's solution for the Mg alloy, showing good structural integrity, no penetrating pores and minimal thickness reduction during the immersion test, with a performance significantly better than that the MgAl 2 O 4 spinel free MAO coating; and (iii) presented excellent biocompatibility and promoted cell proliferation and osteogenic differentiation. The relevant mechanisms through which the MgAl 2 O 4 spinel contributed to construction, biodegradation, biocompatibility, and osseointegration were elaborated. This work is helpful in developing Mg alloys for biomedical applications.