Liposomal Zn- and Al-phthalocyanine enhance photodynamic therapy of oral cancer

Objective: Photodynamic therapy (PDT) has been studied as a promising method to eliminate cancer cells. We used liposomes as a method of specific drug delivery for PDT and studied the effectiveness of the liposome-encapsulated photosensitizers, zinc phthalocyanine (ZnPc) and aluminum phthalocyanine chloride (AlPc), on oral squamous cell carcinoma. Methods: Liposomes were composed of palmitoyloleoyphosphatidylcholine (POPC): phosphatidylglycerol (PG), and contained either ZnPc or AlPc. Free or liposome-encapsulated ZnPc and AlPC were added to HSC-3 cells in the concentration range 0.1-1 µM, and incubated for 24 h at 37°C. The cells were then exposed to light (690 nm) from a High Power LED Multi Chip Emitter. Cytotoxicity was evaluated by the Alamar Blue assay that measures metabolic activity, using a Molecular Devices Versamax microplate reader. Results: Cells treated with ZnPc and AlPc encapsulated in liposomes resulted in further decrease in cell viability when compared to cells treated with free ZnPc and AlPc. The Alamar Blue assay showed a linear reduction with increased concentrations of ZnPc and AlPc in both free and liposomal form. For 0.1, 0.5, and 1 µM liposomal ZnPc, the viability was reduced to 89±4, 69±4, and 41±5%, respectively. With free ZnPc, the values were 104±5, 89±5, and 75±6%, respectively. For 0.1, 0.5, 1 µM liposomal AlPc, the viability was reduced to 54±3, 20±3, and 21±2%, respectively. With free AlPc, the viabilities were 108±5, 78±8, and 51±1%, respectively. Conclusion: HSC-3 cells are vulnerable to liposomal ZnPc and AlPc in a dose-dependent manner, following light activation. Liposomal ZnPc and AlPc both reduce cell metabolic activity more effectively than the free photosensitizers. Our studies indicate that liposomal delivery of ZnPc and AlPc results in a more efficient elimination of oral squamous cell carcinoma