Sulfonated aluminium phthalocyanines as sensitizers for photochemotherapy. Effects of small light doses on localization, dye fluorescence and photosensitivity in V79 cells.

V79 cells incubated with di- or tetrasulfonated aluminium phthalocyanines (AlPcS2 or AlPcS4) showed a granular fluorescence pattern. Co-staining with the lysosomotropic dye acridine orange (AO) indicated that the granules that were stained by these photoactive phthalocyanines were identical to lysosomes. Small light exposures made the lysosomes permeable to the dyes without inactivating the cells. Also, the lysosomal enzymes beta-AGA and cathepsin (L+B) were inactivated by small light exposures when AlPcS4 was present. Such small and almost nontoxic light exposures caused a redistribution of the dyes in the cells that was accompanied by a more than 10-fold increase in the fluorescence quantum yields of the dyes. Surprisingly, this redistribution and increase in fluorescence did not result in any significant increase in the photosensitivity of the cells.