Application of Riboflavin and Curcumin as Natural Photosensitizers for Antimicrobial Photodynamic Inactivation against Staphylococcus aureus: A Study for Skin Disease

Atopic Dermatitis (AD) and Actinic Keratosis (AK) are becoming increasingly prevalent in developing countries, including Indonesia. Staphylococcus aureus, a common microorganism associated with both conditions, presents treatment challenges due to the increasing antibiotic resistance and associated side effects. Photodynamic Inactivation (PDI), which employs natural photosensitizers such as riboflavin and curcumin in combination with Omega Light LED-a technology commonly used in aesthetic treatments-offers a potential alternative. In this study, riboflavin and curcumin were applied separately at a concentration of 0.015% (w/v) and irradiated with red (λ = 640 nm), blue (λ = 423 nm), or green (λ = 532 nm) light using an Omega Light LED device (O'melon). Cell viability was assessed using an ELISA reader at 595 nm after irradiation durations of 10, 30, and 60 minutes. Skin toxicity was predicted using Toxtree 3.1.0, Pred-Skin 3.0, and pkCSM web-based tools. Results showed that the photosensitizers without irradiation were not cytotoxic to Staphylococcus aureus. However, the combination of blue light and photosensitizers significantly inhibited bacterial viability. Riboflavin achieved 49.0±4.8% inhibition within 10 minutes, indicating a rapid but transient effect, whereas curcumin elicited a slower yet sustained antibacterial response, achieving 34.2 ± 1.6% inhibition after 30 minutes. Computational toxicity predictions suggested no clear evidence of skin irritation; however, a potential for skin sensitization remains. These findings support the potential of riboflavin- and curcumin-based PDI using Omega Light LED as a promising non-antibiotic approach for managing Staphylococcus aureus infections in AD and AK.