In vitro biocompatibility and antibacterial behavior of anodic coatings fabricated in an organic phosphate containing solution on Mg-1.0Ca alloys

Magnesium alloys have received considerable attention to potentially serve as biodegradable biomaterials due to their excellent mechanical properties and biological performance. In order to achieve a proper degradation rate, acceptable biocompatibility and good antibacterial ability, magnesium alloys are usually modified by micro arc oxidation (MAO). In this paper, sodium phytate (Na12Phy), one natural organic substance and widely used as food additive, is selected as the main MAO electrolyte. The process of Na12Phy taking part in the coating formation is investigated by characterizing the coating composition and structure. The biocompatibility and antibacterial property of the MAO treated samples are measured by the MTT assay and pellicle sticking method. The results show that magnesium phosphate is developed in the MAO coatings, suggesting that Na12Phy is decomposed into inorganic phosphates and lower myo-inositol phosphate esters due to spark discharge. In vitro biocompatibility evaluated by L-929 cells indicates that both the substrate and MAO samples do not induce toxicity to the cells, meeting the need for use as biomaterials. The MAO samples achieve the antibacterial effect of 99.99% against Staphylococcus aureus and 99.98% against Escherichia coli. After 24 h immersion in E. coli suspensions, the MAO samples have been corroded, indicating that they achieve the excellent antibacterial ability due to their corrosion in the tested suspensions.