Synthesis and electrophoretic deposition of zinc oxide and zinc oxide-bioactive glass composite nanoparticles on AZ31 Mg Alloy for biomedical applications

In the present study, zinc oxide-bioactive glass composite nanoparticles were synthesized through a sonochemical/sol-gel method. The results revealed that the composite nanoparticles consisted of zinc oxide (ZnO) cores (259 +/- 9 nm) surrounded by a thin bioactive glass (BG) shell with 26 +/- 3 nm thickness. The zinc oxide and zinc oxide-bioactive glass composite nanoparticles were electrophoretically deposited on the AZ31 substrate involving an intermediate oxide layer applied using plasma electrolytic oxidation. The composite nature of the zinc oxide-bioactive glass nanoparticles facilitated the application of lower voltages during electrophoretic deposition compared to simultaneous deposition of individual zinc oxide particles. Dopamine was used in the bath as a surfactant and polyethyleneimine as a binder to ensure complete adhesion between coating and substrate. Microscopic examinations confirmed more uniformity in the coatings constituted of composite nanoparticles. Electrochemical impedance spectroscopy in a phosphate-buffered saline solution revealed a significant improvement in barrier performance of the composite coatings compared to the zinc oxide coating. According to the short-term bioactivity evaluations in simulated body fluid, more Ca-P deposits were formed on the composite coating. Furthermore, the adhesion between the coating and substrate increased significantly in this coating, mainly due to the rough surface of the nanoparticles.