Electrophoretic Deposition of Magnesium Oxide Nanoparticles on Magnesium: Processing Parameters, Microstructures, Degradation, and Cytocompatibility.

Magnesium (Mg) and its alloys are a class of promising materials for biodegradable orthopedic and craniomaxillofacial implants; however, rapid release of hydrogen gas remains a key challenge for clinical translation. This study reported the optimal parameters of electrophoretic deposition (EPD), at which magnesium oxide nanoparticles (nMgO) could be deposited onto Mg substrates with homogeneous surface morphology and elemental distribution. The results showed that the distribution and uniformity of the nMgO coatings on Mg improved when the nMgO concentration in ethanol increased and the time of applied voltage decreased. The nMgO-coated Mg showed a homogeneous surface and distinct degradation mode during the 9-day immersion studies in revised simulated body fluid (r-SBF) and Dulbecco's modified Eagle's medium (DMEM), when compared with the noncoated Mg controls. The nMgO coating initially mitigated hydrogen gas formation. The degradation layer on nMgO-coated Mg was thicker than the noncoated Mg and enriched with Ca and P that are favorable for skeletal implant applications. In the direct culture study with bone marrow derived mesenchymal stem cells (BMSCs) in vitro , the cell adhesion density and morphology were not affected by the solubilized degradation products released by the nMgO-coated Mg under indirect contact. However, at the cell-biomaterial interface, the cell spreading decreased under direct contact, possibly because of the continuous dynamic degradation of the samples. The electrophoretically deposited nMgO coatings on Mg-based medical implants should be further studied to improve the coating-substrate and cell-material interfaces for clinical applications.