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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 (TiO 2 ) 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% TiO 2 + 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/cm 2 energy for 1 min, and the number of CFU/mL in log 10 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% TiO 2 + 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.

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This study focuses on the role of photosensitizers in photodynamic therapy. The photosensitizers were prepared in combinations of 110/220 µM erythrosine and/or 10/20 µM demethoxy/bisdemethoxy curcumin with/without 10% (w/w) nano-titanium dioxide. Irradiation was performed with a dental blue light in the 395–480 nm wavelength range, with a power density of 3200 mW/cm2 and yield of 72 J/cm2. The production of ROS and hydroxyl radical was investigated using an electron paramagnetic resonance spectrometer for each individual photosensitizer or in photosensitizer combinations. Subsequently, a PrestoBlue® toxicity test of the gingival fibroblast cells was performed at 6 and 24 h on the eight highest ROS-generating photosensitizers containing curcumin derivatives and erythrosine 220 µM. Finally, the antifungal ability of 22 test photosensitizers, Candida albicans (ATCC 10231), were cultured in biofilm form at 37 °C for 48 h, then the colonies were counted in colony-forming units (CFU/mL) via the drop plate technique, and then the log reduction was calculated. The results showed that at 48 h the test photosensitizers could simultaneously produce both ROS types. All test photosensitizers demonstrated no toxicity on the fibroblast cells. In total, 18 test photosensitizers were able to inhibit Candida albicans similarly to nystatin. Conclusively, 20 µM bisdemethoxy curcumin + 220 µM erythrosine + 10% (w/w) nano-titanium dioxide exerted the highest inhibitory effect on Candida albicans.

Azulene samples in ethanol/distilled water (1, 10 and 100 µm) were irradiated with a 638 nm red laser (0.5 watts, light‐to‐target distance 2 cm, energy density 4 or 40 J cm−2) by either continuous, fractionation or pulse mode. Singlet oxygen in the samples was measured using 10 µm 9,10‐dimethyl anthracene (positive control 10 μm erythrosine) and relative fluorescence intensities were measured at 375/436 nm excitation/emission. Peripheral blood mononuclear cells (PBMCs, 1 × 105cells/well) preincubated with 0.01 μg mL−1 rhTNF‐α for 6 h were cultured with irradiated azulene samples in RPMI‐1640 under standard conditions. PGE2 was quantified by rhPGE2 ELISA kit using a Varioscan® microplate reader at an excitation wavelength of 420 nm. Kruskal Wallis with Dunn`s test was performed at a significance level of P < 0.05. The highest singlet oxygen amount was found in 10 µm azulene samples irradiated at 40 J cm−2 under continuous mode (P = 0.001 when compared with 10 µm erythrosine). PGE2 expression in rhTNF‐α‐induced PBMCs was reduced to 45% of control by 1 µm azulene irradiated at 40 J cm−2 under fractionation mode. Fractionation mode with intermediate laser energy density in the presence of low concentration of azulene could increase singlet oxygen and tend to reduce PGE2.

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Objective Incorporating an enhancer such as nano-titanium dioxide into antimicrobial photodynamic therapy can improve treatment outcome.This study aimed to compare the anticandidal efficacy of photodynamic therapy by erythrosine with nano-titanium dioxide (nano-TiO2) stimulated by a blue light emitting diode with three standard dental antifungal agents. Materials and Methods Candida albicans biofilms on acrylic resin plates were treated for 15 minutes with either nystatin, fluconazole, Polident, 220µM erythrosine + 1% (w/w) nano-TiO2 + 15 J/cm2 blue light photodynamic therapy (Ery PDT), or distilled water. For the Ery PDT group, blue light was applied for 1 minute after incubation. After 1, 3, and 6 hours, the colony forming units in log10 (log10CFU/mL) were compared. The ultrastructure of C. albicans on the acrylic resin plates treated with erythrosine + nano-TiO2 + blue light was examined using transmission electron microscopy at magnification of 30,000x. Results After 1 hour, nystatin, Polident, and Ery PDT indifferently inhibited C. albicans. At 6 hours, Ery PDT reduced the number of viable C. albicans in biofilms by 0.28log10 CFU/mL, which was equal to the effect of fluconazole and Polident. Transmission electron microscopy demonstrated that Ery PDT altered the C. albicans cell morphology by inducing cell wall/membrane rupture. Conclusion Photodynamic therapy with erythrosine + nano-TiO2 + blue light at low light power density (15 J/cm2) was as effective at inhibiting C. albicans biofilm on acrylic resin as fluconazole and Polident.