In vitro biocorrosion, antibacterial and mechanical properties of silicon-containing coatings on the magnesium-hydroxiapatite nanocomposite for implant applications

In this study, to control the rapid degradation rate of Mg/27.5HA nanocomposite, the single-layered Si and double-layered MgO/Si coatings were fabricated on Mg/27.5HA by milling-multi steps pressing-sintering powder metallurgy method. The microstructure, chemical composition and cross-section of the coatings as well as the corrosion products were characterized using FE-SEM, XRD, FT-IR and TEM. The degradation behavior of uncoated, Si- and MgO/Si-coated nanocomposites was examined by impedance measurements, potentiodynamic polarization and weight loss tests. The corrosion resistance of Mg/27.5HA was significantly improved by double-layer MgO/Si coating resulted in the lower corrosion current; 7.9 mA/cm2 versus 187.4 mA/cm2 for the uncoated sample, as well as the higher corrosion potential; −1292.3 versus −1487.3 mVSCE. In addition, immersion tests indicate the decrease in weight loss rate of Si-coated and MgO/Si-coated Mg/27.5HA nanocomposites compared to the uncoated sample. After 28 days of immersion in SBF, much less degradation rates of the Si- and MgO/Si-coated nanocomposites led to the slower losses of the mechanical properties. Antibacterial tests on the bare and coated samples consisting MgO revealed the antibacterial activity against Staphylococcus aureus and Escherichia coli. Moreover, according to the in vitro cell culture test, a significant enhancement in the biocompatibility was obtained for Mg/27.5HA nanocomposite with Si-containing coatings.