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Photodynamic Studies of Metallo 5,10,15,20‐Tetrakis(4‐methoxyphenyl) porphyrin: Photochemical Characterization and Biological Consequences in a Human Carcinoma Cell Line ¶
Author(s) -
Milanesio M. E.,
Alvarez M. G.,
Yslas E. I.,
Borsarelli C. D.,
Silber J. J.,
Rivarola V.,
Durantini E. N.
Publication year - 2001
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2001)0740014psomtm2.0.co2
Subject(s) - chemistry , porphyrin , quantum yield , photochemistry , singlet oxygen , zinc , reaction rate constant , oxygen , organic chemistry , fluorescence , kinetics , physics , quantum mechanics
The photodynamic activities of the free‐base 5,10,15,20‐tetrakis(4‐methoxyphenyl)porphyrin (TMP) and their metal complexes with zinc(II) (ZnTMP), copper(II) (CuTMP) and cadmium(II) (CdTMP) have been compared in two systems: reverse micelle of n ‐heptane/sodium bis(2‐ethylhexyl)sulfosuccinate/water bearing photooxidizable substrates and Hep‐2 human larynx carcinoma cell line. The quantum yields of singlet molecular oxygen, O 2 ( 1 Δ g ), production (Φ Δ ) of TMP, ZnTMP and CdTMP in tetrahydrofuran, were determined yielding values of 0.65, 0.73 and 0.73, respectively, while O 2 ( 1 Δ g ) formation was not detected for CuTMP. In the reverse micellar system, the amino acid l ‐tryptophan (Trp) was used as biological substrate to analyze the O 2 ( 1 Δ g )‐mediated photooxidation. The observed rate constants for Trp photooxidation ( k obs Trp ) were proportional to the sensitizer quantum yield of O 2 ( 1 Δ g ). A value of ∼2 × 10 7 s −1 M −1 was found for the second‐order rate constant of Trp ( k r Try ) in this system. The response of Hep‐2 cells to cytotoxicity photoinduced by these agents in a biological medium was studied. The Hep‐2 cultures were treated with 1 μ M of porphyrin for 24 h at 37°C and the cells exposed to visible light. The cell survival at different light exposure levels was dependent on Φ Δ . Under these conditions, the cytotoxic effect increases in the order: CuTMP ≪ TMP < ZnTMP ∼ CdTMP, correlating with the production of O 2 ( 1 Δ g ). A similar behavior was observed in both the chemical and biological media indicating that the O 2 ( 1 Δ g ) mediation appears to be mainly responsible for the cell inactivation.