Photodynamic inactivation of planktonic cells, pseudohyphae and biofilms Candida albicans by cationic porphyrins

Candidiasis is an opportunistic fungal infection that is considered to be the most common in humans. Recently, Candida albicans infections have increased worldwide due to enlarged use of antifungals and medical devices, such as heart valves, vascular bypasses, dental implants, and catheters, where fungal biofilms can form. In this work, two cationic porphyrins were evaluated as photosensitizing agents for the photodynamic inactivation (PDI) of C. albicans under different culture conditions. The photosensitizers used were 5,10,15-tris[4-(3-N,N,N-trimethylamoniopropoxi)phenyl]-20-(4-trifluormethylphenyl) porphyrin (AB₃) and 5,10,15,20-tetrakis[4-(3-N,N,N-trimethylamoniopropoxy) phenyl]porphyrin (A₄). Both porphyrins were rapidly bound to cells in 5 min. Photodynamic treatment was performed using different concentrations of photosensitizer (0.5-5.0 µM) and different times of irradiation (5-30 min) with white light (90 mW/cm²). C. albicans planktonic cells treated with 2.5 and 5.0 µM were eliminated after 5 and 15 min of irradiation, respectively. The addition of reactive oxygen species scavengers showed that singlet molecular oxygen was involved in the photoinactivation. Also, a contribution of type I mechanism was detected in the yeast inactivation. These agents were also effective to photoinactivate C. albicans pseudohyphae suspended in PBS, producing a reduction of 6 log after 15 min of irradiation. Furthermore, the biofilms of C. albicans that incorporated the porphyrins (5 mM) during the proliferation stage were completely photoinactivated after 60 min of irradiation. Therefore, the results indicate both porphyrins present potential applications as a phototherapeutic agent for fungal inactivation under different culture conditions.