Influence of incubation time and sensitizer localization on meta-tetra(hydroxyphenyl)chlorin (mTHPC)-induced photoinactivation of cells.

Fiche publication

Date publication

août 2007

Journal

Radiation research

Auteurs

Membres identifiés du Cancéropôle Est :
Dr BEZDETNAYA-BOLOTINE Lina , Dr DUMAS Dominique

Tous les auteurs :
Sasnouski S, Pic E, Dumas D, Zorin V, D'Hallewin MA, Guillemin F, Bezdetnaya L

Lien Pubmed

https://www.ncbi.nlm.nih.gov/pubmed/17638401

Résumé

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.