In vitro photodynamic inactivation effects of hypocrellin B on azole-sensitive and resistant Candida albicans

Background and aim The extensive use of antifungal drugs has led to resistance from Candida albicans . The search for alternative treatment against drug-resistant C. albicans is highly desirable. Antimicrobial photodynamic therapy (aPDT) is an emerging and promising approach for treating localized and superficial C. albicans infections. The aim of this study was to investigate the photodynamic inactivation (PDI) effects of hypocrellin B (HB) on azole-sensitive and resistant C. albicans in vitro . Methods The PDI efficacies of HB on standard C. albicans strain (ATCC 10231), azole-sensitive clinical isolate of C. albicans , and azole-resistant clinical isolate of C. albicans were assessed. The uptake of HB in C. albicans cells was investigated by confocal laser scanning microscopy (CLSM). The PDI effects on cellular structure and surface characteristics were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results HB exhibited no significant dark toxicity, but inactivated the azole-sensitive and resistant C. albicans in a light-dose and PS concentration-dependent manner. CLSM images indicated that PDI treated C. albicans cells showed stronger fluorescence compared to untreated cells. TEM images suggested that significant damage to the cell wall, membrane, and cytoplasm were induced by HB-mediated PDI. SEM analysis revealed that the surface of C. albicans cells became twisted and ruptured after PDI treatment. Conclusions Azole-sensitive and resistant C. albicans could be effectively inactivated by HB in the presence of light, and HB-mediated aPDT shows promise as an antifungal treatment for C. albicans .