1 June 1992 Spectroscopic investigation of light-induced intracellular reactions of hydrophilic meso-tetraphenylporphyrins
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Light-induced reactions of different hydrophilic meso-tetraphenyl porphyrins (TPPS4, TPPC4, T4MPyP) were investigated during PDT treatment. These measurements were carried out in vitro using micro-spectrofluorometry and were correlated with measurements in buffer solutions. In the case of the anionic TPPS4, before light exposure, a neutral free base and a protonated species could be detected simultaneously in the cells. During irradiation, the protonated species first disappeared. Due to the fact that a coexistence of a protonated and unprotonated species requires a pH value around 5, TPPS4 was at first located in the lysosomes (pH 5) and was released into the cytoplasm during irradiation as a result of lysosomal rupture. Further light exposure led to a drastic fluorescence formation in the nuclei, in particular the nucleoli of the cells, which was concomitant with a renewed observation of a fluorescence emission spectrum similar to that of the protonated species. In the case of the anionic TPPC4, a similar fluorescence increase was observed during irradiation. However, the formation of a protonated species played a less important role. The cationic T4MPyP again showed fluorescence increase during irradiation. Two Soret-bands separated by about 20 nm could be detected. The red-shifted band may be due to a special intercalation of T4MPyP in nucleic acids.
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Angelika C. Rueck, Wolfgang S. L. Strauss, Herbert Schneckenburger, Rudolf W. Steiner, "Spectroscopic investigation of light-induced intracellular reactions of hydrophilic meso-tetraphenylporphyrins", Proc. SPIE 1645, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy, (1 June 1992); doi: 10.1117/12.60950; https://doi.org/10.1117/12.60950

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