Photodynamic Antimicrobial Chemotherapy (PACT) using methylene blue inhibits the viability of the biofilm produced by Candida albicans

Background: Candida albicans is an opportunistic fungus, an etiological agent of human infections, presenting high rates of morbidity and mortality. The resistance of C. albicans to conventional therapies has been reported due to the extensive use of conventional antifungals. Photodynamic antimicrobial chemotherapy (PACT) is a technique that combines a visible light with a specific wavelength and a photosensitizer, producing ROS and permanent damages in the treated cells. Methods: In this work, the effects of PACT, using Methylene Blue (MB), as a photosensitizer, on C. albicans development were studied. Results: Significant reduction in both cell growth and biofilm formation after PACT were observed, in a dependent manner on both MB concentration and fluence. In the presence of MB 0.02 mg/mL, it was observed inhibition in biofilm formation of 58, 70 and 74%, using fluences of 10, 20 and 30 J/cm(2), respectively. Also, it was observed inhibition of 54, 66 and 55% in the presence of MB 0.01, 0.02 and 0.05 mg/mL, respectively in the viability of biofilm produced by C. albicans. The number of both yeast and filaments present in the structure of biofilm were reduced after PACT. Furthermore, PACT changed the growth kinetics of C. albicans. Interestingly, we demonstrated increase in the extent of lag phase and an alteration in the profile of the exponential phase after PACT. Conclusions: Taken together, these results indicate the potential PACT effects using MB to decrease the C. albicans development.