COMPETITION BETWEEN PHOTOBLEACHING AND FLUORESCENCE INCREASE OF PHOTOSENSITIZING PORPHYRINS AND TETRASULFONATED CHLOROALUMINIUMPHTHALOCYANINE

The time-dependent fluorescence changes of photosensitizing porphyrins and tetrasulphonated chloroaluminiumphthalocyanine (AlClSPc) were measured at different intracellular sites using video-enhanced microscopy and image processing. To obtain variations in intracellular fluorescence intensity, different radiant exposures of a Kr+ laser-pumped dye laser were delivered via a 600 μm plastic-clad silica fibre connected to the microscope. During irradiation, competition between photobleaching and fluorescence increase of the different dyes was observed. The porphyrins normally showed photobleaching, which was dependent on the sensitizer and its specific accumulation within the cell. Photobleaching was less pronounced for hydrophilic uroporphyrin than for more hydrophobic dyes. In contrast with an almost exponential decrease in porphyrin fluorescence with increasing light dose, the fluorescence intensity of AlClSPc significantly increased at the beginning of irradiation, and could be correlated with intracellular deaggregation. © 1990.