Tetraamido-substituted 2,3-naphthalocyanine zinc(II) complexes as phototherapeutic agents: synthesis, comparative photochemical and photobiological studies.

The aim of this study is to report the synthesis and photochemical and phototherapeutic activities of tetraamido-substituted 2,3-naphthalocyanine zinc(II) complexes (ZnNcs 5-8). Four naphthalocyanine complexes, tetrabenzamido- (ZnNc 5), tetramethoxybenzamido- (ZnNc 6), tetrahexylamido- (ZnNc 7) and tetradodecylamido- (ZnNc 8) naphthalocyanine zinc complexes absorbing at around 770 nm were synthesized. The dye-sensitized photo-oxidation of 1,3-diphenylisobenzofuran via 1O2 was studied in more detail in order to compare the quantum yields of these different sensitizers. Pharmacokinetic and photodynamic therapy studies of Lewis lung carcinoma in mice were carried out after administration of liposome incorporated ZnNcs 5-8. The phototherapeutic efficiency was evaluated by changes in the mean tumour diameter with time, regrowth delay (days), average survival time (days) and electron microscopy observations. According to all assessment criteria used, the most promising photosensitizer seems to be tetrabenzamido-substituted ZnNc 5. We suggest that mainly structural properties are the reason for the better results observed. The morphological analysis confirms the mechanism of photonecrosis, which was observed in our previous work with unsubstituted and substituted ZnNcs 1-4. Direct photodamage to the membrane, mitochondria and rough endoplasmic reticulum in the neoplastic cells and delayed photodestruction of the endothelial cells surrounding the tumour tissue were detected. Also, changes in lysosomes were observed. The data presented through different parameters are compared with such obtained for other photodynamic therapy sensitizers.