Evaluation of antifungal activity of visible light-activated doped TiO₂ nanoparticles

Titanium dioxide (TiO₂) is a well-known material for its biomedical applications, among which its implementation as a photosensitizer in photodynamic therapy has attracted considerable interest due to its photocatalytic properties, biocompatibility, high chemical stability, and low toxicity. However, the photoactivation of TiO₂ requires ultraviolet light, which may lead to cell mutation and consequently cancer. To address these challenges, recent research has focused on the incorporation of metal dopants into the TiO₂ lattice to shift the band gap to lower energies by introducing allowed energy states within the band gap, thus ensuring the harnessing of visible light. This study presents the synthesis, characterization, and application of TiO₂ nanoparticles (NPs) in their undoped, doped, and co-doped forms for antimicrobial photodynamic therapy (APDT) against Candida albicans. Blue light with a wavelength of 450 nm was used, with doses ranging from 20 to 60 J/cm² and an NP concentration of 500 µg/ml. It was observed that doping TiO₂ with Cu, Fe, Ag ions, and co-doping Cu:Fe into the TiO₂ nanostructure enhanced the visible light photoactivity of TiO₂ NPs. Experimental studies were done to investigate the effects of different ions doped into the TiO₂ crystal lattice on their structural, optical, morphological, and chemical composition for APDT applications. In particular, Ag-doped TiO₂ emerged as the best candidate, achieving 90-100% eradication of C. albicans.