Fungicidal effect of combined nano TiO₂ with erythrosine for mediated photodynamic therapy on Candida albicans: an in vitro study

Background and objective: Candida albicans is an opportunistic pathogen that can cause oral candidiasis. Antifungal drugs have been used for treatment, but resistance to these drugs has emerged in recent years. Photodynamic therapy is one of the alternative treatments. The purpose of this study was to evaluate the killing of C. albicans biofilms in photodynamic therapy in vitro by erythrosine (Ery) gel on its own or in combination with nano-titanium dioxide (TiO₂) stimulated by blue light (BL). Methods: Four test groups were studied, namely, Ery gel at 220 and 440 μM, in the presence or absence of 1% TiO₂ + BL, and the control group. After C. albicans biofilms were prepared, a photosensitizer was applied to them for 15 min. Test groups were then activated by BL with 15 J/cm² energy for 1 min, and the number of CFU/mL in log₁₀ was compared between the test and control groups. In addition, the generation of reactive oxygen species by the effective photosensitizer was tested by electron spin resonance spectrometer (ESR) using 2,2,6,6-tetramethyl-4-piperidone and 5,5-dimethyl-1-pyrroline N-oxide. Results: C. albicans survival rates were different with statistical significance across all groups by the Kruskal-Wallis test (p < 0.001). The group of 440 μM Ery gel + 1% TiO₂ + BL showed the highest efficacy (p = 0.05). Results of ESR showed that all Ery gel + BL groups generated significantly more singlet oxygen compared with control groups. None of the groups, however, generated detectable levels of hydroxyl radical and superoxide anion. Conclusion: Erythrosine with blue light is an effective photosensitizer that can kill C. albicans, and nano-titanium dioxide acts as a catalyst that enhances the effect of erythrosine.