Electrophoretic deposition of bioactive glass 58S- xSi3N4 (0 < x < 20 wt.%) nanocomposite coating on AISI 316L stainless steel substrate for biomedical applications

This paper aims to investigate the biocompatibility, bioactivity and properties of bioactive glass 58S-xSi₃N₄ (0 < x < 20 wt.%) nanocomposite coating on AISI 316 L stainless steel substrate, applied by electrophoretic deposition method. The implications of adding Si₃N₄ nanoparticles up to 20 wt.% to the bioactive glass coating for the structural and biomedical properties of deposited coatings were investigated. The deposited coating samples were characterized by X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), and energy dispersive X-ray spectroscopy (EDS). For the evaluation of cellular toxicity, the MTT cytotoxicity test with MG63 bone cell was performed. Bioactivity test was also conducted in simulated body fluid (SBF) up to 28 days. Results showed that increase in the Si₃N₄ content of composite samples is associated with a significant decrease in the average size of composite powder, inferring that Si₃N₄ additive has become nucleation sites during synthesis. Stereomicroscope images showed that with an increase in deposition time up to 70 min, a uniform coating can be attained. An increase in the Si₃N₄ content is associated with a significant reduction in surface roughness and non-uniformities of the deposited layer. The addition of Si₃N₄ in the composite layer slightly increases the wetting angle. The highest cellular toxicity was observed for the AISI 316 L sample at the concentration of 10 micromolar, while the lowest cellular toxicity is attributed to the BG-20 %Si₃N₄ sample at the concentration of 75 micromolar, exhibiting viability values similar to the control sample. Bioactivity assessment of deposited coatings indicated a remarkable improvement in the bone-forming ability of Si₃N₄-containing bioactive glass composite.