Comprehensive evaluation of MWCNT/HAp and Cu-functionalized MWCNT/HAp coatings on Ti6Al4V implants: Enhancing surface characteristics and biocompatibility via plasma electrolytic oxidation

This study investigates the evolving relationships and interactions between two distinct materials used in hard tissue implants: multi-walled carbon nanotubes (MWCNTs) and copper nanoparticles (Cu NPs). The surface modification of the Ti6Al4V implant substrate was achieved using hydroxyapatite (HAp) and its composite materials with MWCNTs and Cu-functionalized MWCNTs electrolytes. The plasma electrolytic oxidation (PEO) method was employed to enhance the physicochemical properties of the coatings. Incorporating MWCNTs into the HAp composite significantly improved these properties, resulting in superior overall corrosion resistance. MWCNTs effectively inhibited the corrosion process of the underlying metal substrate and reduced the formation of corrosion products. Additionally, it helped stabilize the HAp particles in the coating, reducing their dissolution in the corrosive environment. Additionally, the PEO process led to the formation of copper oxides (CuO and Cu2O) from Cu NPs, which were carefully analysed for their impact on coating properties. The antibacterial properties of the coatings were attributed to specific mechanisms of copper oxide products, including CuO and Cu2O, which generate reactive oxygen species (ROS) and induce oxidative stress in bacteria. These mechanisms, involving ion release, surface interactions, and intracellular effects, were discussed in detail to explain the observed antibacterial activity. Additionally, this study provides a detailed comparison of MWCNTs and Cu/ MWCNT coatings applied on Ti6Al4V using a HAp-containing electrolyte, highlighting the physicochemical and antibacterial effects and the factors influencing these properties. The findings suggest that these composite coatings offer promising potential for enhancing the performance of dental implants, thereby contributing to better implant longevity and biocompatibility.