Biodegradation and mechanical performance of Silane-chitosan-graphene oxide composite coating on AZ31 magnesium alloys for biomedical applications.

Biodegradable magnesium alloy medical implants have attracted considerable interest thanks to their remarkable biocompatibility and mechanical properties. However, the rapid corrosion rate of magnesium alloys in physiological environments presents a major challenge to their practical application. Therefore, this study attempted to design a silane/chitosan /graphene oxide composite coating that reduces the corrosion and enhances the biodegradation of magnesium alloys used in temporary implants. The composite fabrication process adopted a cost-effective spin-coating technique providing a uniform coating of magnesium alloy substrates. Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) results showed a dense and compact silane/chitosan/graphene oxide (Silane/CS/GO) coating on the magnesium coated alloy surface. The mechanical properties of the fabricated silane/chitosan/graphene oxide composite were also investigated by microindentation and scratch tests. The hardness of the magnesium alloy increased from ~268 HV ±13.4 to ~644.13 HV ± 32.2 upon the application of the coating. Moreover, the results showed that the cohesive critical load (L) of the ternary composite was greater than L ~ 3.02 ± 0.15 N. In addition, compared to uncoated AZ31 alloys, the friction coefficient and wear volume of the ternary composite decreased from ~0.13 ± 0.02 to ~0.07 ± 0.004 and from ~18 to ~0.04 (10μm), respectively. Finally, the corrosion of the composite coating was assessed in simulated body fluid (SBF) in vitro at 37 °C. Hydrogen evolution results revealed that graphene oxide seemed to delay the diffusion of corrosive ions into the Mg matrix, while Silane prevented the coupling of GO graphene oxide sheets to the metal surface. Consequently, silane / chitosan /graphene oxide composite coatings could be a very useful material for coating magnesium implant devices. It contributed to reduce the corrosion of the substrate and alleviate the cost and discomfort of implants.