TiO ₂ Nanotubes Decorated with Ag and Zn Nanoparticles on CP-Ti for Biomedical Applications: Evaluation of Electrochemical and Antibacterial Behavior against Staphylococcus aureus

Premature implant failure caused by corrosion and biofilm formation remains a relevant clinical challenge. Although TiO₂ nanotubular coatings (NTTs) improve the corrosion resistance of titanium, their limited intrinsic antibacterial activity restricts performance in biomedical environments. To address this limitation, this study develops TiO₂ nanotubes functionalized with zinc nanoparticles (Zn.NTTs), produced through a simple and clean photoreduction route, and compares them with silver incorporated nanotubes (Ag.NTTs), widely recognized for their antibacterial efficiency. The novelty of this work lies in demonstrating the direct photoreduction-based incorporation of Zn nanoparticles (NPs) onto NTTs combined with detailed electrochemical and antibacterial evaluations against biofilm-forming Staphylococcus aureus, an approach still little explored. NTTs were synthesized by electrochemical anodization in a glycerol/water electrolyte containing fluoride ions followed by immersion in metal nitrate solutions and UV-A irradiation to promote in situ nanoparticle formation. SEM confirmed the presence of well-organized nanotubes with uniform diameters of 42 ± 5 nm. AFM analyses showed increased surface area, 208% for Ag.NTT and 178% for Zn.NTT relative to CP-T, and quadratic roughness (Sz) values of 1.641 and 1.564 μm, respectively. TEM revealed nanoparticle diameters of 14 ± 3 nm for Ag and 17 ± 2 nm for Zn. XPS confirmed metallic (Ag⁰, Zn⁰) and oxidized (Ag₂O, ZnO) species, indicating partial oxidation after photoreduction. Electrochemical tests in simulated body fluid (SBF) demonstrated that Ag.NTT and Zn.NTT coatings exhibit enhanced resistive and capacitive behavior compared with NTT and CP-Ti, attributed to the formation of Ag₂O and ZnO, which generate stable passivation regions and reinforce the corrosion barrier. Antibacterial assays showed inhibition zones of 4.0 ± 0.8 mm for Ag.NTT and 1.3 ± 0.8 mm for Zn.NTT. These results demonstrate that Zn.NTT provides a combination of enhanced corrosion resistance and antibacterial action, highlighting its potential use for titanium-based biomedical implants.