SERUM-ALBUMIN AS A VEHICLE FOR ZINC PHTHALOCYANINE - PHOTODYNAMIC ACTIVITIES IN SOLID TUMOR-MODELS

Zinc phthalocyanine (ZnPc) is a second-generation photosensitiser for the photodynamic therapy (PDT) of cancer. Unsubstituted ZnPc is, howev er, highly insoluble in most common solvents, and for clinical applica tions the material needs to be incorporated in liposomes. We report a simple, alternative procedure to formulate ZnPc through non-covalent b inding to bovine serum albumin (BSA). Intravenous administration of Zn Pc-BSA preparations, at a molar ratio of 11:1 and at a ZnPc dose equiv alent to 0.5 mol kg(-1), to tumour-bearing mice followed 24 h later by PDT was shown to provide tumour control in two different models, the EMT-6 tumour in Balb/c mice and the human colon T380 carcinoma in nude mice. Analysis of serum fractions from treated animals showed that Zn Pc readily redistributes over the serum high-density lipoprotein (HDL) fraction. We also demonstrated the absence of hepatic toxicity of the ZnPc-BSA preparation by monitoring the hepatic cytochrome P450 activi y in treated animals and the viability of human cultured hepatocytes.