Photodynamic activity of 5,10,15,20-tetrakis (4-methoxyphenyl)porphyrin on the Hep-2 human carcinoma cell line: Effect of light dose and wavelength range

The photodynamic activity of 5,10,15,20-trtmkis(4-methoxyphenyl)porphyrin (TMP) has been investigated in two systems: reverse micelles of n-heptane/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water-bearing photooxidizable substrates and on a Hep-2 human carcinoma cell line. The effect of variation in the light dose and wavelength range (360-800, 455-800. and 590-800 nm) was compared in both media. The aerobic singlet oxygen-mediated photooxidation of L-tryptophan (Trp) was used as a model of biological substrate in a micellar system. A considerable increase of the observed rate constants of Trp (k(obs)(Trp)) was noted, increasing the irradiated area of the TMP spectrum. In vitro, the survival curves of Hep-2 cells. treated with TMP. were markedly dependent on the light wavelength ranges used for irradiation. A linear behavior between k(obs)(Trp) and the photoinactivation rate of Hep-2 cells was found, indicating that the singlet oxygen (O-1(2)) is the main species responsible for cell inactivation. These results contributed to an understanding of the photodynamic process yielded by this porphyrin in vitro and the sensitivity of Hep-2 cells to photodamage. (C) 2001 Academic Press.