Method: Reference strains of Candida tropicalis (ATCC 4563) and Candida glabrata (ATCC 2001) were included in this study. Standard suspensions of each strain were obtained and then 100µL of the suspensions were transferred to 96-well microtiter plates. The samples were photosensitized with 20µM-Curcumin (CUR) and exposed to 5.28, 2.64 and 1.32 J/cm2 of LED light fluence. Control suspensions were treated with CUR only, or not exposed to LED light or CUR. Aliquots of experimental and control samples were serial diluted and plated in duplicate on Sabouraud Dextrose Agar. After plates incubation (37°C for 48 h), colonies were counted and the colony-forming unit per milliliter were calculated (CFU/ml). Metabolic activity of samples was measured by XTT reduction assay. The XTT solution was prepared by adding 1.5ml of XTT in 300µL of menadione solution (0.4M). Then, 12µL of this solution was added to each samples and incubated in dark (37°C/ 3h). After this, the proportional colorimetric changes were analyzed in a microtiter plate reader at 492 nm. The experiments were performed with ten replicates for each condition and data were statistically analyzed using Kruskal Wallis and Dunn test (α=5%).
Result: A significant reduction on C. glabrata growth and metabolism were seen with the use of 2.64 and 5.28J/cm2. Similar findings were found for C. tropicalis, but for this species the metabolism were comparable among the three light fluencies used. The absence of colony growth and cell metabolism were not observed for any Candida species after photodynamic treatment.
Conclusion: Curcumin-mediated PDT proved to be effective to reduce the metabolic activity and colony growth of different Candida species.