Photodynamic activity of 5,10,15,20-tetrakis (4-methoxyphenyl)porphyrin onthe 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/so dium bis(2-ethylhexyl)sulfosuccinate (AOT)/water-bearing photooxidizable su bstrates 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) w as compared in both media. The aerobic singlet oxygen-mediated photooxidati on of L-tryptophan (Trp) was used as a model of biological substrate in a m icellar system. A considerable increase of the observed rate constants of T rp (k(obs)(Trp)) was noted, increasing the irradiated area of the TMP spect rum. In vitro, the survival curves of Hep-2 cells. treated with TMP. were m arkedly dependent on the light wavelength ranges used for irradiation. A li near behavior between k(obs)(Trp) and the photoinactivation rate of Hep-2 c ells was found, indicating that the singlet oxygen (O-1(2)) is the main spe cies responsible for cell inactivation. These results contributed to an und erstanding of the photodynamic process yielded by this porphyrin in vitro a nd the sensitivity of Hep-2 cells to photodamage. (C) 2001 Academic Press.