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1 August 2007 Influence of Incubation Time and Sensitizer Localization on Meta-tetra(hydroxyphenyl)chlorin (mTHPC)-Induced Photoinactivation of Cells
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Abstract

Sasnouski, S., Pic, E., Dumas, D., Zorin, V., D'Hallewin, M-A., Guillemin, F. and Bezdetnaya, L. Influence of Incubation Time and Sensitizer Localization on Meta-tetra(hydroxyphenyl)chlorin (mTHPC)-Induced Photoinactivation of Cells. Radiat. Res. 168, 209–217 (2007).

The present study addresses the impact of different aggregation states of meta-tetra(hydroxyphenyl)chlorin (mTHPC) on the photoinactivation of cells. Measurements of the photophysical properties of mTHPC in MCF-7 cells showed progressive sensitizer aggregation with increasing incubation time. Reconstructed absorption spectra of intracellular mTHPC showed a significant decrease in the molar extinction coefficient and broadening of the Soret band at 24 h incubation compared to 3 h. Intracellular photobleaching of mTHPC slowed down, and the profile changed from mono- to bi-exponential upon incubation. Fluorescence lifetime imaging (FLIM) measurements revealed a substantial decrease in the lifetime of mTHPC fluorescence at 24 h compared to 3 h. In addition, the intracellular localization of mTHPC as observed by fluorescence microscopy changed from a diffuse homogeneous fluorescence pattern at short incubation times to a punctiform pattern at 24 h. The efficiency of photodynamic therapy (PDT) assessed by a clonogenic assay was three times greater at 24 h. However, when the survival curves were replotted as a function of the number of absorbed photons, the efficiency was 1.8 times greater at 3 h than at 24 h. The loss of photosensitizing efficiency at higher mTHPC concentrations was attributed to self-quenching of the triplet states of the sensitizers.

Siarhei Sasnouski, Emilie Pic, Dominique Dumas, Vladimir Zorin, Marie-Ange D'Hallewin, François Guillemin, and Lina Bezdetnaya "Influence of Incubation Time and Sensitizer Localization on Meta-tetra(hydroxyphenyl)chlorin (mTHPC)-Induced Photoinactivation of Cells," Radiation Research 168(2), 209-217, (1 August 2007). https://doi.org/10.1667/0033-7587(2007)168[209:IOITAS]2.0.CO;2
Received: 14 November 2006; Accepted: 1 February 2007; Published: 1 August 2007
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