There has been considerable interest in the development of novel photosensitisers for photodynamic therapy (PDT). The use of liposomes as drug delivery systems containing simultaneously two or more drugs is an attractive idea to create a new platform for PDT application. Therefore, the aim of this study was to evaluate the synergistic effect of diethyldithiocarbamate (DETC) and zinc phthalocyanine (PDT) co-encapsulated in liposomes. The reverse-phase evaporation method resulted in the successful encapsulation of DETC and ZnPc in liposomes, with encapsulation efficiencies above 85 %, mean size of 308 nm, and zeta potential of - 36 mV. The co-encapsulation decreased the cytotoxic effects in mouse embryo fibroblast (NIH3T3) cells and inhibited damage to human erythrocytes compared to free DETC + ZnPc. In addition, both the free drugs and co-encapsulated ones promoted more pronounced phototoxic effects on human breast cancer cells (MDA-MB231) compared to treatment with ZnPc alone. This synergistic effect was determined by DETC-induced decreases in the antioxidant enzyme activity of superoxide dismutase (SOD) and glutathione (GSH).
Keywords: Diethyldithiocarbamate; Liposomes; Photodynamic therapy; Phototoxicity; Synergistic effect; Zinc phthalocyanine.
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