Photodynamic cell killing effects and acute skin photosensitivity of aluminum-chloro-tetrasulfonated phthalocyanine and hematoporphyrin derivative.

UNLABELLED

Aluminum-chloro-tetrasulfonated phthalocyanine (PC) showing an absorption peak at 678 nm was compared to hematoporphyrin derivative (HpD), a photosensitizer commonly used in the photodynamic therapy (PDT) of cancers.

IN VITRO STUDIES

KK-47 cells were exposed to long-wavelength ultraviolet (UVA) or red light (greater than 600 nm, greater than 640 nm and greater than 660 nm) after drug sensitization. With UVA irradiation, a higher photodynamic cell killing effect was observed in the cells treated with HpD than with PC. However, with red light irradiation (both greater than 640 nm and greater than 660 nm) PC resulted in greater cell damage. PC was less toxic to KK-47 cells in the dark. In vivo studies: Using a gold vapor laser (GVL: 627.8 nm, 200 mW/cm2, 200 J/cm2), the photodynamic tumor response was determined in C3H/He mice bearing transplantable squamous cell carcinoma. No significant difference was observed in the tumor volume between the PC and HpD groups, except that the PC group (10.0 mg/kg body weight) showed a significantly higher remission rate (3/6) than the control group (0/10, P less than 0.05). Skin photosensitivity test: Skin photosensitivity was estimated by measuring changes in back skin thickness due to photosensitization. With UVA irradiation, a stronger skin reaction was observed in the HpD group, while with visible light irradiation there was no significant difference between the HpD and PC groups. Based on the superior cell killing effect with red light, reduced toxicity to the cells in the dark and mild skin reaction with UVA, PC may be a more promising photosensitizer for PDT.