Preparation of the phycoerythrin subunit liposome in a photodynamic experiment on liver cancer cells 1

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.