Efficient photodynamic inactivation of Candida albicans by porphyrin and potassium iodide co-encapsulation in micelles

Photodynamic inactivation of bacterial and fungal pathogens is a promising alternative to the extensive use of conventional single-target antibiotics and antifungal agents. The combination of photosensitizers and adjuvants can improve the photodynamic inactivation efficiency. In this regard, it has been shown that the use of potassium iodide (KI) as adjuvant increases pathogen killing. Following our interest in this topic, we performed the co-encapsulation of a neutral porphyrin photosensitizer (designated as P1) and Kl into micelles and tested the obtained nanoformulations against the human pathogenic fungus Candida albicans. The results of this study showed that the micelles containing P1 and Kl displayed a better photodynamic performance towards C. albicans than P1 and Kl in solution. It is noteworthy that higher concentrations of Kl within the micelles resulted in increased killing of C. albicans. Subcellular localization studies by confocal fluorescence microscopy revealed that P1 was localized in the cell cytoplasm, but not in the nuclei or mitochondria. Overall, our results show that a nanoformulation containing a photosensitizer plus an adjuvant is a promising approach for increasing the efficiency of photodynamic treatment. Actually, the use of this strategy allows a considerable decrease in the amount of both photosensitizer and adjuvant required to achieve pathogen killing.