Tailoring Graphene Oxide-Infused Hydroxyapatite Coatings on Titanium: Electrochemical Insights and Simulation for Enhanced Bone Implant Performance.

Abstract

Inspired by the self-healing capabilities of skeletal tissues, advanced osteoinductive treatments, such as calcium phosphate ceramics, have been developed to improve bone repair. Hydroxyapatite (HAP), renowned for its osteoconductive and osteoinductive properties, is commonly used in dental and orthopedic implants. However, HAP's mechanical limitations under load-bearing conditions drive the need for composites that incorporate reinforcing materials. Graphene, with its superior surface area, conductivity, mechanical strength, and biocompatibility, is an ideal candidate for enhancing HAP composites. This study explores the development of graphene oxide (GO)-based nano HAP (n-HAP/GO) composite coating via electrophoretic deposition (EPD) on titanium (Grade-2) surfaces, optimizing deposition voltages (60-90 V) and time (3 min) to achieve uniform, adherent, and crack-free coatings. Various characterization techniques, including high-resolution transmission electron microscopy (HR-TEM), high-resolution scanning electron microscopy (HR-SEM), optical microscope, contact angle measurement, and electrochemical analyses (open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS)), were employed to assess morphology, bioactivity, and corrosion resistance. Results indicate that coatings deposited at 80 V for 3 min exhibited better characteristics including reduced porosity, enhanced hydrophilicity, and improved corrosion resistance, which records the highest corrosion potential (<i>E</i> _corr) (-164.16 mV vs SCE) and the lowest corrosion current density (<i>i</i> _corr) (39.848 nA/cm²). COMSOL Multiphysics software was used to analyze changes in coating thickness due to variations in coating parameters (voltages, time, and bath concentration). The results demonstrate that adjusting the coating voltage to 80 V produced a more controlled and desirable coating thickness of 21.0 to 22.5 μm, which aligns with experimental findings. Additionally, antibacterial tests confirmed enhanced activity against <i>S. aureus</i> and <i>E. coli</i>. The findings of the study suggest that n-HAP/GO composite coatings prepared by EPD at 80 V for 3 min significantly improve the bioactivity and corrosion resistance of titanium implants, offering promising applications in bone implants and infection prevention.