TiO2 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.