Acta Pharmacologica Sinica 2008 December; 29 (12): 1539-1546; doi: 10.1111/j.1745-7254.2008.00886.x

Aim: Efforts are underway to establish a preparation method for the phycoerythrin subunit (PE-sub) liposome, and enhance the cellular uptake and photodynamic therapy (PDT) effect on cancer cells.

Methods: A film dispersion method was used to prepare the PE-sub liposome, an orthogonal analysis was conducted to optimize the PE-sub liposome preparation condition and determine the effects of liposomes as carriers on cell uptake in vitro. Under a fluorescence microscope, the cell survival rate of normal liver cell line HL7702 and liver cancer cell line HepG2 was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was determined with flow cytometry and acridine orange staining after PDT treatment.

Results: The optimum preparation conditions of the PE-sub liposome were found: a phosphatidylcholine-to-cholesterin ratio of 1:2, a PE-sub-to_lipid ratio of 1:30, 20 mL buffer volume, 10 min sonication time, and an average encapsulation rate of up to 47.2%. The particle size ranged from 80 to 200 nm, and the average particle diameter was 136 nm. At a concentration of 100 μg/mL, the transfection rate of the PE-sub liposome reached 18% at 2 h and 24% at 4 h, and remained steady at 5_6 h. The half lethal dose of PDT on HepG2 was 75 μg/mL, whereas the cell survival rate of HL7702 reached 80% at the same dosage. The PDT-treated cells showed characteristics of apoptosis

Conclusion: The film dispersion method was found to maintain the biological characteristics of the PE-sub. The use of the liposome carrier increased the PE-sub accumulation in the cells and enhanced its PDT effect on HepG2 compared to the PE-sub. HL7702 cell toxicity on had less apparent change after PDT treatment. The PE-sub liposome demonstrated good tumor-targeting characteristics in the in vitro experiment.

Keywords: phycoerythrin subunit; liposome; photodynamic therapy; liver cancer cell