Photodynamic inactivation of yeast sensitized by porphyrins substituted by amino groups

EZEQUIEL D. QUIROGA, M. GABRIELA ALVAREZ, S. JIMENA MORA, M. ELISA MILANESIO Y EDGARDO N. DURANTINI

San Juan

Congreso; 2da Reunión Conjunta Sociedades de Biología; 2011

The development of new therapeutic alternatives such as photodynamic inactivation (PDI) is necessary due to antimicrobial resistance. The PDI is based on the incorporation of the sensitizer in microbial cells and the subsequent illumination with visible light induces lethal damage in cells. In this study the photodynamic activity of 5,10,15,20-tetrakis [4-(3-N,N-dimethylaminopropoxy) phenyl]porphyrin (TAPP) and 5,10,15,20-tetrakis [4-(3-N,N,Ntrimethylaminepropoxy) phenyl]porphyrin (TAPP4+) were compared on Candida albicans. The quantum yields of singlet molecular oxygen were 0.74 and 0.72 for TAPP and TAPP4+, respectively. The cultures treated with 5 ìM porphyrin showed a binding of 1,04 for TAPP and 1.5 nmol/106 cells for TAPP4+ after 30 min of incubation. Cell survival with both sensitizers caused a decrease of ~5 log, after 30 min of irradiation. The PDI was also confirmed by the delay in the growth curves of C. albicans. Studies of fluorescence microscopy showed that the sensitizers are located in an irregular manner into the cells. TAPP+4 presents positive charges on the periphery of the macrocycle, while TAPP bears aliphatic amino groups. At physiological pH, these amino groups are in equilibrium with the protonated form giving intrinsic positive charges on the agent. This effect can significantly increase its activity in the PDI.