Photodynamic Treatment of Yeast With Chloroaluminum‐phthalocyanine: Role of the Monomeric Form of the Dye

The effect of photodynamic treatment on the yeast Kluyveromyces marxianus with aluminum‐phthalocyanines has been studied. It was found that the nonsulfonated sensitizer caused light‐dependent loss of colony‐forming capacity, whereas the mono‐ and tetrasulfonated forms did not induce loss of clonogenicity. The effect of the nonsulfonated sensitizer increased with longer preincubation periods of cells with the dye. Formation of cellattached, mostly intracellularly localized monomelic sensitizer also increased with time. The amount of cell‐bound multimeric nonsulfonated phthalocyanine did not vary with time. Experiments designed to specifically increase the amount of cell‐attached monomers led also to an increased photoinactivation of the cells. It is therefore concluded that the photodynamic effect of the nonsulfonated Al‐phthalocyanine is mediated by the monomeric form of the dye.