Electrophoretic coating of magnesium oxide on microarc-oxidized titanium and characterization of in vitro antibacterial activity and biocompatibility

Titanium (Ti) orthopaedic implants modifed by micro-arc oxidation (MAO) are satisfactory in biocompatibility but prone to risks of infection. Antibacterial but still biocompatible coatings are required for these devices. Magnesium oxide (MgO) nanoparticles have been reported to be toxic to a variety of bacteria and relatively safe to cells in vitro. Electrophoretic deposition (EPD) is a fast and convenient technique for depositing nanoparticle-based coatings while retaining their nano-particular nature. Conversely, MAO creates a possible surface topography for the the mechanical adhesion of EPD coatings. Therefore, the present study investigated EPD of MgO coatings on MAO-treated Ti and evaluated in vitro antibacterial properties and biocompatibility. MgO coatings were prepared on micro-arc oxidized Ti (MAO-Ti) by electrophoretic deposition for 15 to 60 s. After culture with Staphylococcus aureus (S. aureus) for 24 h, the MgO-coated samples reduced the bacterial numbers by 81 % to 98 % (vs. MAO-Ti) in a dose-dependent manner. Crystal violet staining confirmed significant reduced biofilm formation on MgO-coated samples. In in vitro osteoblast culture, samples treated by EPD for 45 or 60 s were cytotoxic (viability<70 %) on days 1 and 3, but all samples became non-cytotoxic on day 5. Moreover, MgO-coated samples increased in vitro mineralization of rat pre-osteoblasts. These results indicate that, MgO coatings prepared by EPD may provide reasonable in vitro antibacterial activities and cytocompatibility.