Biodegradable magnesium alloy coated with TiO2/MgO two-layer composite via magnetic sputtering for orthopedic applications: A study on the surface characterization,corrosion, and biocompatibility

In this study, a coating of thin TiO₂ layer and a TiO₂/MgO double layer were created on the surface of AZ91D alloy by magnetic sputtering method in order to improve the corrosion and biocompatibility properties of this alloy. The microstructural studies by field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) showed that coatings were formed continuously and homogeneously on the alloy surface. In the double-layer coating, MgTiO₃ and Mg₂TiO₄ compounds were formed at the coating/substrate interface in addition to TiO₂ and MgO phases as the main phases in the coating structure. The results of corrosion test showed that in general, coating improves the corrosion of AZ91D alloy in simulated-body fluid (SBF). The double-layer coating showed the best corrosion resistance at a corrosion current of 5.743 × 10^?7 μA/cm² and a corrosion potential of ?1.513 V due to its cathodic protection of the substrate and blockage of the path of the corrosive solution towards the substrate. In vitro tests showed that considering the good match between the used materials as the coating and body, no toxic material exits which results in improvement in biocompatibility, adhesion, and bone-cell multiplication.