title: Influence of incubation time and sensitizer localization on meta-tetra(hydroxyphenyl)chlorin (mTHPC)-induced photoinactivation of cells.
abstract: 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.
authors.affiliation: CRAN UMR 7039 CNRS, INPL, UHP, Centre Alexis Vautrin, Vandoeuvre-Les-Nancy, France.
authors.forename: Siarhei
authors.initials: S
authors.lastname: Sasnouski
authors.forename: Emilie
authors.initials: E
authors.lastname: Pic
authors.forename: Dominique
authors.initials: D
authors.lastname: Dumas
authors.forename: Vladimir
authors.initials: V
authors.lastname: Zorin
authors.forename: Marie-Ange
authors.initials: MA
authors.lastname: D'Hallewin
authors.forename: François
authors.initials: F
authors.lastname: Guillemin
authors.forename: Lina
authors.initials: L
authors.lastname: Bezdetnaya
mesh_terms: D000042:Absorption; D045744:Cell Line, Tumor; D006801:Humans; D008652:Mesoporphyrins / Q000493:pharmacokinetics / Q000494:pharmacology*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D008652:Mesoporphyrins; D017319:Photosensitizing Agents; C072269:temoporfin