Abstract Magnesium and its alloys have attracted considerable attention as biodegradable implants due to their biodegradability, mechanical properties comparable to bone, excellent biocompatibility, and high bioactivity. The main challenge of magnesium-based implants is their poor corrosion resistance in physiological environments. Therefore, controlling the degradation or corrosion rate of magnesium alloys is crucial for safe biomedical applications. Various polymeric, ceramic, and composite coatings have been applied to enhance the corrosion resistance, bioactivity, and biocompatibility of magnesium alloys. According to the available research, the polycaprolactone-carbon nanotube-copper oxide coating on magnesium alloy has not been thoroughly investigated so far. Thus, the aim of the present study is to eva‎luate the corrosion resistance and antimicrobial properties of a polycaprolactone-carbon nanotube-copper oxide coating on magnesium alloy for medical applications. In this study, impedance test results showed that the addition of 0.5% and 1% by weight of reinforcing agents to the coating increased the corrosion resistance by approximately 5.5 and 12 times, respectively. Furthermore, the presence of 0.5% and 1% by weight of reinforcing agents in the coating increased the charge transfer resistance by approximately 37 and 118 times, respectively. Polarization test results also indicated that the corrosion potential shifted toward more positive values with the addition of reinforcing agents to the coating and with an increase in these agents up to 1% by weight. Additionally, Tafel extrapolation from polarization test results revealed that the corrosion current density decreased with the addition of carbon nanotubes and CuO to the PCL-based coating and with an increase in their concentration up to 1% by weight. The contact angle test results also showed a significant increase in the contact angle with the addition of 0.5% and 1% by weight of CNT and CuO to the PCL polymer, which was attributed to the hydrophobic nature of the coating in the presence of reinforcing agents. Moreover, the antibacterial test demonstrated that the antibacterial properties of the substrate improved with the addition of reinforcing materials. In the bioactivity test conducted in simulated body fluid (SBF), it was observed that the apatite formation increased with the addition of 0.5% and 1% by weight of reinforcing agents to the coating, making the coating suitable for in vivo implantation.

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