Photoinduced Reactions of Porphyrin Photosensitizers B: Hydrophilic Meso — Theraphenylporphyrins
Light-induced reactions of the hydrophilic meso-tetraphenylphorphyrin-tetra-suifonate (TPPS4) were investigated during PDT-treatment. These measurements were carried out in vitro using microspectrofluorometry and were correlated with measurements in buffer solutions. Before light exposure neutral free base and dictation of this porphyrin could be detected simultaneously in the cells. During irradiation (6J/cm2) the dication disappeared. Due to the fact, that coexistence of these protonated and unprotonated species requires a pH value around 5, we deduce that the sensitizers were first of all localized in the lysosomes (pH 5) and were released into the cytoplasm (pH 7) during irradiation as a result of lysosomal rupture. Further light exposure (12J/cm2) led to a drastic fluorescence formation in the nuclei and the nucleoli of the cells which was concomitant with a renewed observation of a fluorescenceemission spectrum similar to that of a protonated meso-te-traphenylporphyrin.
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