BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES–III. PHOTOINACTIVATION OF V‐79 CHINESE HAMSTER CELLS BY TETRASULFOPHTHALOCYANINES*

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Abstract
Abstract—Tetrasulfophthalocyanine and a series of its metal chelates were tested for their ability to photoinactivate V‐79 Chinese hamster cells. Incubation of cells for 1 h with tetrasulfophthalocyanine at 5 μMeffectively sensitized cells towards red light. At the 1% survival level, the dye was 4 x more efficient than hematoporphyrin, efficiency being defined in terms of drug concentration in the medium and incident light fluence rather than on the basis of quanta absorbed. Chelation of the dye with metal ions resulted in most cases in a greatly diminished photosensitizing effect, except for cerium. The cerium complex was about 5 x more effective for cell killing than the metal free tetrasulfophthalocyanine and 20 x more efficient as compared to hematoporphyrin. Hypoxic conditions resulted in total loss of photoactivity indicating the involvement of oxygen in the action mechanism. The inactivation by near‐UV light by these drugs was also investigated. The potential of sulfonated phthalocyanines as novel photosensitizers for photodynamic cancer therapy is discussed.