Intracellular distribution of photosensitizing porphyrins measured by video-enhanced fluorescence microscopy.

The intracellular distribution of photosensitizing porphyrins with different amounts of aggregates was measured in a fluorescence microscope using video-intensified detection and image processing. Porphyrin fluorescence was localized in the plasma membrane, cytoplasm, nuclear membrane and nucleoli. The fluorescence intensity in the plasma membrane decreased with increasing aggregation of the photosensitizers. In addition, a redistribution of the porphyrin molecules from the plasma membrane to the nuclear membrane and adjacent intracellular sites was observed with increasing incubation time. Photobleaching of porphyrin fluorescence was most pronounced in the plasma membrane and least efficient within the nucleoli.