Fusogenic liposomes prepared with polyethyleneglycol-lipid

Liposomes have been widely accepted in biotechnology and medicine as a vehicle for the delivery into cells of various substances, eg. DNA, RNA, enzymes, or drugs. In order for biologically unstable compounds to be internalized into cells, fusion is favored because the liposome-loading compounds are directly delivered into the cytosol and able to avoid destruction by lysosomal enzymes. From this point of view, we have developed a fusogenic liposome, which contains an artificial lipid, polyethyleneglycol-lipid (PEG-lipid) or polyethyleneglycol-substituted cholesterol (PEG-chol). The fusogenicity of these functionalized liposomes to carrot protoplasts and human lymphocytes was investigated. Egg PC liposomes with 23 Mole% PEG-lipid (n = 11) were the most effective in fusing with carrot protoplasts. The fusogenicity of PEG-chol containing liposomes was significantly less. The difference in the fusogenicity between the two liposomes is ascribed to the difference in hydration capacity and fluidity of liposomal membranes. In the case of human lymphocytes, fusion was observed only at 4.0 °C, and endocytosis occurred at 37°C.