Abstract: BACKGROUND AND AIM: To investigate the skin phototoxicity of di-sulfo-di-phthalimidomethyl phthalolcyanine zinc (ZnPcS2 P2)-based-photodynamic therapy. MATERIALS AND METHODS: Kunming mice were assigned to five dose groups,receiving intravenous administration of 0.9％NS at 0.2 ml/10 g body weight,the solvent at 0.2 ml/10 g body weight,hemoporphyrin injection at dosage of 15 mg/kg body weight, ZnPcS2 P2 at dosages of 2 or 5 mg/kg body weight. Mice were exposed to simulated sunlight (10,20,30,40 mW/cm2) 1,3,24,48,72,96 h and 7 d after a single intravenous injection.Skin phototoxicity was investigated by the weight of the slices taken from earflaps by perforex(diameter=6 mm). RESULTS: When mice were exposed to light(40 mW/cm2) 1,3,24 h after dosing, there were significant differences of the weight of ears between ZnPcS2 P2(2 or 5 mg/kg) and control groups(P<0.05). There were no significant findings in ZnPcS2 P2(2 mg/kg)ZnPcS2 P2 group 48 h after dosing,and in ZnPcS2 P2(5 mg/kg) group 7 d after dosing.When ZnPcS2 P2(2 mg/kg) group was exposed to light(10,20,30,40 mW/cm2) 1 or 3 hr after administration, there were significant differences of the weight of ears between 10 mW/cm2 and 20，30，40 mW/cm2 groups(P<0.05). CONCLUSION: In Kunming mice ZnPcS2 P2(2 mg/kg) caused phototoxicity 1,3，24 h after administration, the potential for phototoxicity was essentially gone after 48 h.Phototoxicity was gone in the skin of mice exposed to simulated sunlight 7 d after injection of ZnPcS2 P2(5 mg/kg). ZnPcS2 P2(2 mg/kg) caused skin phototoxicity,the saturated irradiance of the light was 20 mW/cm2.

Key words: photodynamic therapy, phototoxicity, photosensitizer