Multi-functional ceramic hybrid coatings on biodegradable AZ31 Mg implants: electrochemical, tribological and quantum chemical aspects for orthopaedic applications

Abstract

Application of biodegradable implants has received increasing attention for the treatment of bone damage due to their low adverse effects. To achieve better biocompatibility and enhanced corrosion resistance of biodegradable implants with improved wear resistance, multifunctional coatings need to be developed. Herein, a ceramic hybrid coating has been fabricated by a plasma electrolytic oxidation (PEO) technique using Ta₂O₅ nanoparticle inclusion on AZ31 Mg alloy in order to attain superior corrosion, wear behavior, and surface porosity that enable improved bioactivity. X-ray diffraction analysis of PEO coatings showed that the surface coating is mainly composed of Mg₃(PO₄)₂, MgO and Ta₂O₅ in different quantities based on PEO processing. Furthermore, scanning electron microscopy (SEM) analysis was employed to observe the surface of the resultant PEO hybrid coatings after and before wear tests. With Ta₂O₅ nanoparticles, PEO coatings showed excellent wear compared with pure PEO coatings. The efficiency of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements in simulated body fluid. Furthermore, in vitro cell culture studies were performed on MG-63 human cells to evaluate the biocompatibility of PEO coatings. A quantum chemical approach and force-field molecular dynamics simulation were employed to evaluate the interaction between the AZ31 Mg surface and PEO hybrid coatings. All of the observations evidently showed that the ceramic hybrid PEO coating provides improved wear and corrosion protection performance with superior biocompatibility with Ta₂O₅ nanoparticles, when compared to pure PEO coatings, due to its synergistic beneficial effect.