Combined bisdemethoxycurcumin and potassium iodide-mediated antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy is emerging as a promising way to treat infections with minimal side effects. Typically, a single photosensitizer used in photodynamic therapy is capable of generating only one type of reactive oxygen species, which may have inadequate capability to eradicate certain types of microbes, especially Candida species. Thus, the use of combined photosensitizers is examined as a means of achieving superior antimicrobial results. We postulate that bisdemethoxycurcumin, a type I reactive oxygen species generator, combined with potassium iodide, an antimicrobial iodide molecule, might exhibit superior antimicrobial effects compared to a single photosensitizer-mediated photodynamic therapy. The effects of bisdemethoxycurcumin + potassium iodide + dental blue light on Candida albicans reduction were examined. Candida biofilms were treated with 20, 40 or 80 μM bisdemethoxycurcumin, 100 mM potassium iodide or a combination of these species for 20 min before irradiation with a dental blue light (90 J/cm²). The negative and positive controls were phosphate buffer saline and nystatin at 1 : 100,000 units/ml, respectively. Candidal numbers were quantified at 0, 1, 6 and 24 h. Hydroxyl radicals were spectrophotometrically measured using 2-[6-(4'amino phynoxyl-3H-xanthen-3-on-9-yl)] benzoic acid or APF probe-mediated fluorescence intensity (Varioskan) at 490/515 nm (excitation/emission). Candidal counts and hydroxyl radical comparisons were performed using the Kruskal-Wallis test and one-way ANOVA, respectively. Correlations between candidal numbers and hydroxyl radical levels were done with a Pearson correlation test. Forty μM bisdemethoxycurcumin+100 mM KI could provide a 3.5 log₁₀ CFU/ml reduction after 6 h. Bisdemethoxycurcumin alone generated OH levels that were strongly correlated with candidal reduction. In conclusion, 40 μM bisdemethoxycurcumin+100 mM KI could reduce C. albicans biofilm.