Antibacterial activity of bioceramic coatings on Mg and its alloys created by plasma electrolytic oxidation (PEO): A review

Mg and its alloys are suitable choices for implant materials due to their biodegradability and biocompatibility features. However, the high electrochemical activity of this family of biomaterials results in their fast degradation and severe corrosion in the physiological environment, producing hydrogen (H2) gas, and therefore increasing the pH of the environment. To meet the clinical requirements, the degradation rate of Mg biomaterials needs to be reduced. Nevertheless, higher corrosion resistance of Mg results in a low alkaline pH, weakening the antibacterial activity. Therefore, while the rapid degradation problem of Mg-based biomaterials needs to be addressed, good antibacterial properties are also necessary. By using the plasma electrolytic oxidation (PEO) surface modification technique, the antibacterial activity of Mg and its alloys can be enhanced while maintaining their corrosion protection properties at a high level. Throughout the PEO process, introducing antibacterial agents into solutions results in a major increase in antibacterial activity of the coatings. Moreover, post- or pre-processing on PEO coatings can provide better protection against bacteria. In this review, the antibacterial activity of PEO coatings applied on Mg and also its alloys will be discussed in more detail.