PHOTOSENSITIZATION OF BACTERIA TO VISIBLE-LIGHT BY MESOSUBSTITUTED PORPHYRINS

Porphine derivatives bearing 2 or 4 cationic substituents in the meso positions of the tetrapyrrolic macrocycle are predominantly bound by the cytoplasmic membrane of Gram(+) and Gram(-) bacteria and, upon visible light irradiation, photosensitize an efficient inactivation of both bacterial types (over 99% killing upon 10 min irradiation with four 250 W tungsten lamps in the presence of 8.4 mu M photosensitizer). On the contrary, anionic meso-substituted porphines as well as one anionic peripherally substituted porphyrin (haematoporphyrin) are photoactive only toward Gram(+) bacteria in spite of efficient binding to the membrane of Gram(-) species and close similarity with the cationic analogues in the photogeneration of cytotoxic intermediate species.