Investigation of the Photodynamic Effects of Curcumin Against Candida albicans

Abstract

This study describes the association of curcumin with light emitting diode (LED) for the inactivation of Candida albicans. Suspensions of Candida were treated with nine curcumin concentrations and exposed to LED at different fluences. The protocol that showed the best outcomes for Candida inactivation was selected to evaluate the effect of the preirradiation time (PIT) on photodynamic therapy (PDT) effectiveness, the uptake of curcumin by C. albicans cells and the possible involvement of singlet oxygen in the photodynamic action. Curcumin-mediated PDT was also assessed against biofilms. In addition to the microbiological experiments, similar protocols were tested on a macrophage cell line and the effect was evaluated by Methyltetrazolium assay (MTT) and SEM analysis. The optical properties of curcumin were investigated as a function of illumination fluence. When compared with the control group, a statistically significant reduction in C. albicans viability was observed after PDT (P < 0.05), for both planktonic and biofilm cultures. Photodynamic effect was greatly increased with the presence of curcumin in the surrounding media and the PIT of 20 min improved PDT effectiveness against biofilms. Although PDT was phototoxic to macrophages, the therapy was more effective in inactivating the yeast cell than the defense cell. The spectral changes showed a high photobleaching rate of curcumin.

Susceptibility of clinical isolates of Candida to photodynamic effects of curcumin

“…In addition, no evidence of colony growth was observed for C. albicans and C. tropicalis isolates after photosensitization with 20 mM of CUR and illumination at 5.28 and 18 J/cm 2 of LED light, respectively. These results are in agreement with those recently published in which a reference strain of C. albicans (ATCC 90028) was efficiently killed after CUR-mediated PDT [23]. The photodynamic effect of CUR against Candida species has not been widely documented in the medical literature, but its antibacterial effect has been described with the use of comparable CUR concentrations (1-25 mM) and light fluences (0.5-30 J/cm 2 ) [26].…”

“…Some previous investigations have already suggested that CUR per se may have antifungal properties [29,30] and its combination with light has been proposed in order to improve its antifungal action [23]. The results showed that the use of CUR in association with light was able to promote a significant antifungal effect against the planktonic form of the yeasts.…”

“…A stock solution of CUR (600 mM) was prepared in DMSO and then diluted in saline solution to obtain the concentrations to be tested. A light emitting diode (LED) based device, composed of eight royal blue LEDs (LXHL-PR09, Luxeon 1 III Emitter, Lumileds Lighting, San Jose, CA), was used to excite CUR [23]. The LED device provided a uniform emission from 440 to 460 nm, with maximum emission at 455 nm.…”

“…Aliquots of 100 ml of the standardized suspensions of Candida were individually transferred to separate wells of a 96-well microtitre plate. Curcumin solutions were added to the wells to give the final concentrations of 5, 10, and 20 mM, which correspond to 1.8, 3.7, and 7.4 mg/l [23]. After dark incubation for 20 minutes (pre-irradiation time), the plate was placed on the LED device and illumination was performed at 5.28, 18, 25.5, and 37.5 J/cm 2 (PDT groups).…”

“…An increasing number of investigations have suggested that CUR exhibits potential therapeutic applications that may be enhanced by combination with light, as it displays a high light absorption in the visible spectral region, around 400-500 nm [23][24][25][26]. Recently, this natural compound has been shown to possess phototoxic potential against yeast cells [23].…”