Antimicrobial photodynamic therapy as a new approach for the treatment of vulvovaginal candidiasis: preliminary results.

In this work, we present the efficacy of photodynamic therapy against yeast cells in an animal model. We tested two photosensitizers, methylene blue and protoporphyrin IX. Thirty-seven female BALB-c mice with a body mass of 20-25 g were used. To achieve persistent vaginitis, estrus was induced by subcutaneous injection of 0.1 mg/mL estradiol valerate applied weekly. Three days after pseudo-estrus, intravaginal inoculation with Candida albicans was performed. Mice were anesthetized with ketamine (80 mg/kg) and xylazine (10 mg/kg) by intraperitoneal injection before inoculation, and antimicrobial photodynamic therapy (aPDT) was performed 5 days after fungal inoculation. Two photosensitizers were tested, methylene blue (MB; 100 µM) and protoporphyrin IX (PpNetNI; 10 µM). Two custom-made LEDs emitting light at 660 and 630 nm at approximately 800 mW each were used for irradiation. The aPDT treatment reduced the fungal colony-forming units (CFUs) by one order of magnitude for the MB (p = 0.020) and PpNetNI (p = 0.018) photosensitizers. Seven days after the treatment, there were significantly fewer CFUs compared to the control group (p = 0.041 and p = 0.035 for MB and PpNetNI, respectively), but this was not increased compared to the initial number immediately after aPDT. Using aPDT as a therapeutic option to decrease fungal infection in a vaginal candidiasis model resulted in a significant reduction in the C. albicans population. Both photosensitizers were effective for preventing reinfection within 7 days. The aPDT also had no effect on the vaginal mucosa at the ultrastructural level. In addition to the fungicide effect, we observed reduced swelling and lack of the formation of abscesses, microabscesses coating the cornified epithelial layer, and the accumulation of neutrophils in the submucosa.

Antimicrobial photodynamic therapy on Candida albicans pre-treated by fluconazole delayed yeast inactivation.

Antimicrobial photodynamic therapy (APDI) has been used to treat localized infection and the aim of this study was to evaluate the effect of APDI combined with fluconazole in suspension of Candida albicans. C. albicans ATCC90028 was subcultured onto Sabouraud agar and inocula were prepared at yeast density of 1×10(6)CFU/mL. Methylene blue (MB) was used with concentration of 100mM. Yeast cells were incubated for 30min in 24-well plate and then irradiated by LED (660nm; 690mW; A=2.7cm(2); I=250mW/cm(2)) with radiant exposure of 30, 60, and 120J/cm(2). The same APDI setup was used with 2h fluconazole (0.5µg/mL) incubation. A UV-vis optical absorption spectroscopy was achieved following fractionated irradiation up to 960s. There were substantial differences in the killing effect following MB-mediated APDI and C. albicans was eradicated in the both APDI groups. The fluconazole combined to APDI delayed the complete inactivation of the yeast (p<0.05). Spectroscopy showed a decrease in absorption following irradiation for all absorption peaks. APDI presented an antagonist effect in the presence of fluconazole.

Photodynamic inactivation of Candida albicans biofilm: Influence of the radiant energy and photosensitizer charge.

BACKGROUND: The aim of this study is to investigate the photoinactivation of C. albicans biofilm on acrylic resin discs (the standard material for dental prosthesis) using the photosensitizers Methylene Blue and a Protoporphyrin IX. METHODS: Eighteen thermally activated Methyl Methacrylate Polymers were used for the biofilm growth of Candida albicans ATCC 10231. Two photosensitizers were tested: methylene blue (50µM) and protoporphyrin IX (10µM). Two custom-made LEDs emitting at 660nm and 630nm with approximately 800mW each were used for the irradiation, with duration ranging from 2 to 10min. RESULTS: This study demonstrates that MB decreased the aPDT CFUs by approximately two orders of magnitude, but the protoporphyrin was ineffective. CONCLUSION: The aPDT with MB significantly reduces (but does not sterilize) the amount of CFU after 10min of irradiation, and it is not dose-dependent. The lack of effect of the protoporphyrin is likely because the negative charges of the proteoglycans present in the extracellular matrix repel the negative charges of the PS, thus preventing its diffusion in the cells.

Aggregatibacter actinomycetemcomitans biofilm can be inactivated by methylene blue-mediated photodynamic therapy.

BACKGROUND: The purpose of this study was to evaluate the antibacterial effects of photodynamic action of methylene blue (MB) against Aggregatibacter actinomycetemcomitans organized on biofilm. METHODS: After the biofilm growth in 96 flat-bottom well plate, the following groups were used: control group, untreated by either laser or photosensitizer (PS); MB group or dark toxicity group, which was exposed to MB alone (100µM) for 1min (pre-irradiation time); laser group, irradiated with laser for 5min in the absence of PS and three antimicrobial photodynamic inactivation (APDI) groups, with three exposure times of 1, 3 and 5min of irradiation, corresponding to fluences of 15, 45, and 75J/cm(2) respectively. The results were compared to the control group for statistical proposes. Scanning electronic microscope analysis was used to access structural changes in biofilm. RESULTS: Red laser alone and MB alone were not able to inactivate bacterial biofilm. APDI groups showed differences when compared to the control group and they were dependent on the exposure time. No statistically significant differences were observed among the APDI groups at 1 and 3min of irradiation. On the other hand, 5min of APDI showed 99.85% of bacterial reduction (p=0.0004). In addition, the biofilm loose its structure following 5min APDI. CONCLUSIONS: The results of this study suggest that A. actinomycetemcomitans biofilm can be inactivated by MB mediated APDI.