Development of HAp/GO/Ag coating on 316 LVM implant for medical applications

In this study, antibacterial activity, biocompatibility, and corrosion resistance of 316 LVM implants were improved using the development of HAp/GO/Ag nanocomposite coatings by the dip-coating method. The XRD and FTIR results confirmed the synthesis of HAp/GO/Ag nanocomposites. HAp/Ag nanoparticles (68 nm) bound to epoxy, hydroxyl, and carboxyl functional groups on GO sheets (size of GO sheets varies from 255 to 1480 nm) by electrostatic interaction. FESEM images showed that HAp/GO/Ag coatings had higher density and fewer micro-cracks than pure HAp coatings. In addition, HAp/GO/Ag coatings showed optimized nano-hardness (4.5 GPa) and elasticity modulus (123 GPa). The results of potentiodynamic polarization demonstrated that HAp/GO/Ag coating has the lowest corrosion current density (0.31 μA/cm²), maximum protection efficiency (90.0%), and lowest release of Fe, Cr, and Ni ions (31, 24, and 15 ppb). In addition, EIS results showed that HAp/GO/Ag coatings could prevent electrolyte access to the substrate and provide high bio-corrosion resistance. A bone-like layer is formed on nanocomposite coatings after 28 days in SBF, proving that Ag and GO's addition does not interfere with the mineralization process. After 28 days of immersion in SBF, the lowest release of Fe, Cr, and Ni ions is related to nanocomposite coatings. Also, the release of Ag⁺ ions from the coatings is between 0.13 and 1.41, providing antibacterial activity without cytotoxicity. HAp/GO, HAp/Ag, and HAp/GO/Ag nanocomposites kill 47%, 92%, and 98% of E. coli bacteria, respectively. HAp/GO, HAp/Ag, and HAp/GO/Ag nanocomposites kill 47%, 92%, and 98% of E. coli bacteria, respectively. The cell culture results showed that human MG-63 osteoblast-like cells in contact with HAp/GO/Ag coating had the highest biocompatibility (98% of cells survived). Therefore, the development of HAp/GO/Ag nanocomposite coating on 316 LVM implant shows improved properties of nano hardness, corrosion resistance, antibacterial activity, and biocompatibility properties, which is a new turning point for nanocomposite coatings for medical applications.