Effects of fluence rate on cell survival and photobleaching in meta-tetra-(hydroxyphenyl)chlorin-photosensitized Colo 26 multicell tumor spheroids.
Fiche publication
Date publication
mars 2001
Journal
Photochemistry and photobiology
Auteurs
Membres identifiés du Cancéropôle Est :
Dr BEZDETNAYA-BOLOTINE Lina
Tous les auteurs :
Coutier S, Mitra S, Bezdetnaya LN, Parache RM, Georgakoudi I, Foster TH, Guillemin F
Lien Pubmed
Résumé
We report the influence of fluence rate on the photobleaching and cell survival in Colo 26 multicell spheroids photosensitized by meta-tetra-(hydroxyphenyl)chlorin (mTHPC). Photosensitizer degradation and therapeutic efficacy increased dramatically and progressively when the fluence rate was reduced over the range from 90 to 5 mW cm-2. These experimental results were compared to a mathematical model of photobleaching based on self-sensitized singlet oxygen reactions with the photosensitizer ground state. This model incorporates photophysical parameters obtained from microelectrode measurements of oxygen depletion at the surface of mTHPC-sensitized spheroids and was refined by including the inhomogeneous distribution of mTHPC in spheroids and oxygen depletion in the bulk medium. Since the model is consistent with the experimental data we conclude that the fluence rate dependence of the cell survival and of mTHPC photobleaching is due to photochemical oxygen consumption and a predominantly singlet oxygen-mediated mechanism of mTHPC photobleaching. The threshold dose of reacting singlet oxygen was calculated to be 7.9 +/- 2.2 mM in this system.
Mots clés
Animals, Cell Survival, drug effects, Colorectal Neoplasms, metabolism, Mesoporphyrins, metabolism, Mice, Photosensitizing Agents, metabolism, Tumor Cells, Cultured
Référence
Photochem. Photobiol.. 2001 Mar;73(3):297-303