Blue-light activated molybdenum cluster-based photosensitizers in NaDES – formulated creams for dermatological photodynamic therapy

Photodynamic therapy (PDT) emerges as an innovative strategy combining light and drug treatment. The most prevalent use of this therapy is for the elimination of cancerous and pre-cancerous cells. However, in recent years PDT has been shown to be a suitable approach to combat the rising threat of antimicrobial resistance through the photoinactivation of pathogenic bacteria. Photosensitizers predicated on octahedral hexa-molybdenum cluster (Mo₆) complexes activated by blue light were formulated into semi-solid topical pharmaceutics containing three distinct types of Mo₆ clusters as potential novel actives for cosmetics purposes. For the first time, semi-solid cosmetic formulations were developed utilizing natural deep eutectic solvents as carriers of these active compounds and tested for their stability, viscosity, skin penetration, and singlet oxygen formation. After that, negligible toxicity for human cells was confirmed using in vitro testing on HaCaT cell lines. Finally, photoinactivation of the most prevalent skin bacterial pathogens Staphylococcus aureus and Cutibacterium acnes was demonstrated under mild conditions that preserve viability of natural symbiotic skin microflora.