Antifungal Efficacy of TiO2 Nanoparticles Under Ultraviolet Irradiation

摘要

In this study, Candida albicans (C. albicans), the most common pathogen fungus in oral disease, was employed to investigate the antifungal activity of photocatalytic TiO2 nanoparticles P25. The antifungal experiment was conducted in two groups of P25 with different concentrations (0.2 mg mL(-1) and 0.4 mg mL(-1)) under ultraviolet A (UVA) and ultraviolet C (UVC) irradiation, respectively. Hydroxyl radicals were detected using electron paramagnetic resonance spectrometer (EPR). TiO2 nanoparticles with the concentration of 0.4 mg mL(-1) under UVA irradiation produced more hydroxyl radicals than other groups. However, no significant decrease of colonies was observed when C. albicans was exposed to irradiation for 15 min with the existence of P25. The maximum and minimum survival rate of C. albicans was 80.7% under UVA with 0.4 mg mL(-1) P25 and 3.2% under UVC with 0.2 mg mL(-1) P25, respectively. Under UVA irradiation, C. albicans containing TiO2 nanoparticles showed little decrease of fungal activity, while the amount of fungus in the suspension under UVC irradiation was significantly reduced. However, the great antifungal efficacy of UVC irradiation cannot be excluded. The scanning electron microscope (SEM) images demonstrated that the adsorption of P25 on C. albicans was associated with the concentration of P25. The higher the concentration was, the more obvious the agglomeration was formed between microorganisms and P25 nanoparticles. Under the UV irradiation, TiO2 nanoparticles performed a "sun block" effect for C. albicans with low photocatalytic antifungal efficacy while the suspension without TiO2 nanoparticles was inactivated faster. TiO2 nanoparticles P25 under UVA or UVC irradiation showed photocatalytic activity despite the fact that the antifungal activity of P25 under UV after 15 min became weak. Furthermore, no additional antifungal effects of P25 under UVA or UVC were observed.