| Abstract: | The effect of the central metal atom on the photodynamic activity of phthalocyanine dyes has been estimated by cytotoxicity to cultured Chinese hamster cells. Chloroaluminium phthalocyanine,, followed by the Zn- derivate, were found to be the only active dyes. In parallel it was found that visible light (615 +/- 10 nm) excitation of phthalocyanines dissolved in dimethylsulphoxide in the presence of oxygen generates superoxide radical anion. O2- radicals were spin--trapped with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and identified by electron spin resonance. The quantum yields for O2- generation range from 10(-5) (Zn-phthalocyanine) to 4.2 X 10(-4) (Ga-phthalocyanine). The efficiency of generating O2- was apparently uncorrelated with the phototoxicity of the same dyes. Furthermore, the biological photodamage could not be inhibited by the addition of superoxide dismutase. It is concluded that O2- is involved very little, if at all, in the phthalocyanine-induced photo-killing of mammalian cells. |
