Investigating a nanocomposite coating of cerium oxide/merwinite via PEO/ EPD for enhanced biocorrosion resistance, bioactivity and antibacterial activity of magnesium-based implants

Magnesium alloys have gained attention as potential biodegradable metallic biomaterials due to their mechanical properties akin to human bone. However, their rapid corrosion within the body prior to full bone fracture healing presents a significant challenge. Hence, our study aimed to address their drawbacks by employing a cerium oxide/merwinite nanocomposite coating. In this investigation, we sought to enhance corrosion resistance and antibacterial properties by depositing a porous cerium oxide layer onto AZ31 magnesium alloy via plasma electrolytic oxidation (PEO), while improving biocompatibility through a secondary merwinite silicate coating applied via electrophoretic deposition (EPD). Surface morphology and chemical composition were analyzed using Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive Spectroscopy (EDS) pre- and post-immersion in Simulated Body Fluid (SBF). Coating phases were examined through X-ray Diffraction (XRD), antibacterial efficacy was evaluated via viable cell counts in contact with Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive), and corrosion resistance was assessed using Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) tests following SBF immersion. Furthermore, adhesion and toxicity were investigated to assess biocompatibility. The findings revealed that the composite coating exhibited a higher calcium-to-phosphate ratio (Ca/P = 1.31) along with enhanced cell adhesion, increased cell viability, reduced toxicity, and 99.99 % antibacterial activity.