Photosensitization of Colpoda inflata cysts by meso-substituted cationic porphyrins

Abstract

Colpoda inflata cysts accumulate significantly large amounts of meso-substituted cationic porphyrins, including meso-tetrakis(N-methyl-4-pyridyl)porphine (TMP-C1) and its mono-N-methyldecyl (TMP-C10) and -tetradecyl (TMP-C14) analogues, upon incubation for 1 h with 1–48 µM porphyrin concentrations. All three porphyrins at concentrations greater than 10 µM exhibited a significant toxicity toward the cysts, in particular lowering the degree of excystment. Upon visible light irradiation of the porphyrin-loaded cysts, extensive photodamage was observed even in the presence of 1 µM porphyrin, as shown by light microscopy observations and counting of vegetative emerging cells. The presence of one decyl or tetradecyl hydrocarbon chain caused about 10-fold enhancement of the phototoxic effects.