Cell uptake of Zn(II)-phthalocyanine-containing liposomes by clathrin-mediated endocytosis

The study of uptake mechanisms of therapeutic drugs has a growing interest in biomedical research. In this work the cell uptake and phototoxicity of the photosensitizer Zn(II)-phthalocyanine (ZnPc) in dipalmitoyl-phosphatidyl-choline liposomes have been studied in the presence or absence of inhibitors of macropinocytosis (cytochalasin D), and clathrin-mediated endocytosis (dynasore). No differences in the uptake or photodynamic damage were observed in A-549 cells subjected to incubation with either ZnPc alone or in combination with cytochalasin D. On the contrary, co-incubation of A-549 cells with ZnPc and dynasore resulted in a significant decrease of photodamage as well as negligible uptake of the photosensitizer. These results indicate that ZnPc is internalized into cells preferentially by a mechanism of clathrin-mediated endocytosis.