Review of the biocompatibility of micro-arc oxidation coated titanium alloys

• Electrolyte and electrical parameters play important roles in micro-arc oxidation.
• SBF immersing is the most widely used method in biological assessment of bioactive coatings.
• More cells are adsorbed and proliferate on a well crystallized HA coating than on an amorphous HA coating.
• The use of hybrid methods could prepare high content of Ca–P ceramic coatings or crystallized HA directly.
• Further discussion of the mechanism of micro-arc oxidation is extremely needed.

Titanium and its alloys are expected to be ideal materials for biomedical applications. Various approaches have been used for biological properties improvement. Among various surface modification techniques, micro-arc oxidation (MAO), which can produce porous, adhesive and bioactive coatings for implantation, has aroused considerable attention. This paper gives a brief overview of biological assessment of bioactive coatings. It focuses mainly on the strategies of improving biological properties of MAO coated titanium and its alloys. The influence of the electrolyte, process parameters, pretreatment and post-treatment on the coating characteristics (surface micrograph, adhesion strength and biological compatibility etc.) is detailed in this article. MAO assisted by other methods to achieve superior biocompatibility is also discussed. Finally, the trend of development in the future is forecasted.

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