Electrochemical Deposition of Copper on Bioactive Porous Titanium Dioxide Layer: Antibacterial and Pro-Osteogenic Activities

Ti surfaces must exhibit antibacterial activity without cytotoxicity to promote bone reconstruction and prevent infection simultaneously. In this study, we employed a two-step electrochemical treatment process, namely, microarc oxidation (MAO) and cathodic electrochemical deposition (CED), to modify Ti surfaces. During the MAO step, a porous TiO2 (pTiO(2)) layer with a surface roughness of approximately 2.0 mu m was generated on the Ti surface, and in the CED step, Cu was deposited onto the pTiO(2) layer on the Ti surface, forming Cu@pTiO(2). Cu@pTiO(2) exhibited a similar structure, adhesion strength, and crystal phase to pTiO(2). Moreover, X-ray photoelectron spectroscopy (XPS) confirmed the presence of Cu in Cu@pTiO(2) at an approximate concentration of 1.0 atom %. Cu@pTiO(2) demonstrated a sustained release of Cu ions for a minimum of 28 days in a simulated in vivo environment. In vitro experiments revealed that Cu@pTiO(2) effectively eradicated approximately 99% of Staphylococcus aureus and Escherichia coli and inhibited biofilm formation, in contrast to the Ti and pTiO(2) surfaces. Moreover, Cu@pTiO(2) supported the proliferation of osteoblast-like cells at a rate comparable to that observed on the Ti and pTiO(2) surfaces. Similar to pTiO(2), Cu@pTiO(2) promoted the calcification of osteoblast-like cells compared with Ti. In summary, we successfully conferred antibacterial and pro-osteogenic activities to Ti surfaces without inducing cytotoxic effects or structural and mechanical alterations in pTiO(2) through the application of MAO and CED processes. Moreover, we found that the pTiO(2) layer promoted bacterial growth and biofilm formation more effectively than the Ti surface, highlighting the potential drawbacks of rough and porous surfaces. Our findings provide fundamental insights into the surface design of Ti-based medical devices for bone reconstruction and infection prevention.