Curcumin-mediated anti-microbial photodynamic therapy against Candida dubliniensis biofilms

The purpose of this study was to evaluate the effectiveness of anti-microbial photodynamic therapy (aPDT) mediated by curcumin (Cur) associated with LED light against biofilms of Candida dubliniensis, and further, investigate cellular uptake and drug penetration through the biofilms under confocal laser scanning microscopy (CLSM). Four C. dubliniensis strains were tested: three clinical isolates from HIV-positive patients and one reference strain (CBS 7987). Biofilms were treated with three Cur concentrations (20.0, 30.0, and 40.0 μM). All samples were incubated in the dark for 20 min and exposed to a 5.28 J/cm² of LED light fluence. Additional samples of each strain were treated either with Cur or LED light only. Control samples had neither Cur nor light. After aPDT, results were read using the XTT salt reduction method. The data were statistically analyzed by two-way ANOVA followed by Games-Howell post-hoc test (α = 0.05). Confocal laser scanning microscopy was used to verify both the uptake of Cur by yeast cells and its penetration through the biofilm. The results showed that aPDT promoted significant reduction on the metabolism of the biofilm-organized cells of C. dubliniensis. Further, while Cur was rapidly taken up by C. dubliniensis cells, a longer time interval was required to allow Cur penetration into biofilm cells. Based on these results, aPDT associating LED and Cur presents promising potential on fungal control of biofilms of C. dubliniensis.