Enhancing the efficacy of antimicrobial photodynamic therapy through curcumin modifications

Curcumin serves as a photosensitizer (PS) in the context of microbial inactivation when subjected to light exposure, to produce reactive oxygen species, which exhibit efficacy in eradicating microorganisms. This remarkable property underscores the growing potential of antimicrobial photodynamic therapy (aPDT) in the ongoing fight against bacterial infections. Considering this, we investigate the efficacy of various in vitro curcumin formulations within a PDT protocol designed to target Staphylococcus aureus. Specifically, we conduct a comparative analysis involving synthetic curcumin (Cur-Syn) and curcumin derivatives modified with chlorine (Cl), selenium (Se), and iodine (I) (Cur-Cl, Cur-Se, Cur-I). To assess the impact of aPDT, we subject S. aureus to incubation with curcumin, followed by irradiation at 450 nm with energy doses of 3.75, 7.5, and 15 J/cm². Our investigation encompasses an evaluation of PS uptake and photobleaching across the various curcumin variants. Notably, all three modifications (Cur-Cl, Cur-Se, Cur-I) induce a significant reduction in bacterial viability, approximately achieving a 3-log reduction. Interestingly, the uptake kinetics of Cur-Syn and Cur-Se exhibit similarities, reaching saturation after 20 min. Our findings suggest that modifications to curcumin have a discernible impact on the photodynamic properties of the PS molecule.