In the presence of oxygen, reactive oxygen species or free radicals are produced, causing cell damage by disrupting the cytoplasmic membrane; the increased permeability causes damage to intracellular

targets and reduces the formation of germ tubes. 14, 15, 16 and 17 The main photosensitizers used in antifungal PDT are phenothiazine dyes, phthalocyanines and porphyrins associated with lasers and other non-coherent light sources.12, 18, 19 and 20 Erythrosine has attracted AZD6244 clinical trial interest as a photosensitizer because it is not toxic to the host and has already been approved for use in dentistry.21 Erythrosine is used to detect dental biofilms. This dye has shown potent photodynamic activity and can reduce 3.0–3.7 log10 of Streptococcus mutans biofilm. 21 and 22 Light-emitting diodes (LEDs) have been suggested as alternative light sources to lasers due to their wider emission bands, smaller size, reduced weight and cost, greater flexibility in treatment irradiation time and easy operation.23 and 24 LEDs are used in dentistry as bleaching tools that do not damage oral tissues. LEDs have shown potent activity in PDT and lack of absence of antimicrobial action alone.19, 25 and 26 In PDT against Candida spp., red and blue LEDs were used with phenothiazines (methylene blue PI3K inhibitor and toluidine blue) and Photogem photosensitizers, reducing planktonic cultures by 3.41 log10 and biofilms by less than 1 log10. 19,

25 and 26 However, the effect of erythrosine dye and green LEDs against Candida spp. has not been described. The aim of this study was to evaluate the effect

of PDT mediated by erythrosine dye and green LEDs on planktonic cultures and biofilms of C. albicans and C. dubliniensis. Erythrosine (Aldrich Chemical Co., Milwaukee, WI, USA) was used for the sensitization of yeasts. Erythrosine solution was prepared by dissolving the powdered dye in phosphate-buffered saline (PBS, pH 7.4) and sterilized by filtration through 0.22-μm pore diameter membranes (MFS, Dublin, CA, EUA). After filtration, the dye solution was stored in the dark. The absorption spectrum (400–800 nm) many of the erythrosine solution (1.0 μM in PBS) was verified in a spectrophotometer (Cary 50 Bio, Varian Inc., Palo Alto, CA, USA) coupled to a microcomputer. A green light-emitting diode (LED) (MMOptics, São Carlos, SP, Brazil) was used as the light source with a wavelength of 532 ± 10 nm, an output power of 90 mW, an energy of 16.2 J, a time of 3 min, a fluence rate of 237 mW cm−2 and a fluence of 42.63 J cm−2. The area irradiated in planktonic cultures and biofilms was 0.38 cm2. The temperature at the bottom of the 96-well microtiter plates (Costar Corning, New York, NY, USA) was monitored using an infrared thermometer (MX4, Raytek, Sorocaba, SP, Brazil); no increases in temperature were observed after irradiation with the LED. Reference strains of C. albicans (ATCC 18804) and C.