EVALUATION OF PORPHYRIN CHARACTERISTICS REQUIRED FOR PHOTODYNAMIC THERAPY

Abstract
— The cytotoxicity (in the dark), phototoxicity (red light) and subcellular localization (using confocal laser scanning microscopy) were determined for 15 porphyrins (1–15) in C6 glioma cells. The partition coefficient in 2‐octanol was also determined for each porphyrin at pH 7.4. The cytotoxicity increased with π (log of partition coefficient) up to π values of +2. The 7 porphyrins with cationic side chains exhibited a classical parabolic correlation between phototoxicity and π, with maximal activity at a π value of approximately 1.0. There was also a significant correlation between subcellular localization and degree of phototoxicity, with the three most photosensitive porphyrins all possessing cationic side chains, and all three localizing in mitochondria.