Diopside/graphene-oxide nanocomposite coatings on AZ31 Mg alloy for biomedical applications: Surface characteristics, corrosion, and biocompatibility properties

Abstract

Surface functionalization of magnesium (Mg)-based alloys with coatings, represents a promising approach to improve the biocompatibility and corrosion resistance of these biodegradable materials for bone tissue engineering. In this study, electrophoretic deposition (EPD) was employed to apply diopside-graphene oxide (Dio/xGO) coatings at different GO concentrations (x= 0, 0.03, 0.06, and 0.12 g/L) onto AZ31 alloy. The study aimed to compare the surface characteristics, corrosion resistance, bioactivity, antibacterial property, and cytocompatibility of these coatings with the uncoated substrate. Diopside (CaMgSi2O6) powder was synthesized using the sol-gel method. FESEM imaging revealed that Dio/0.06GO nanocomposite coating exhibited a more compact morphology compared to the other ones. AFM studies indicated an increase in surface roughness with higher GO concentration, with a Sa=293.80 ± 23.75 nm measured in the Dio/0.12GO sample. A similar trend was observed in the coatings' wettability. The Dio/0.06GO coating exhibited the highest corrosion resistance, with a corrosion current density (icorr) 91.5% lower than the uncoated Mg alloy. Furthermore, apatite deposits with the highest Ca/P atomic ratio (1.61) formed on this coating after seven days of immersion in simulated body fluid (SBF), indicating its superior bioactivity compared to the other ones. Results from the antibacterial activity test showed that GO, particularly at higher concentrations, exhibited bactericidal effect against E. coli and S. aureus. In vitro cellular studies indicated that although Dio/0.12GO coating displayed the most favorable MCT3T-E1 osteoblast cellular adhesion, the highest cell viability (92.17 ± 1.2%) was associated with the Dio/0.6GO deposits. In conclusion, Dio/GO nanocomposite coatings showed the potential to improve corrosion resistance and biological properties in Mg alloy orthopedic applications.