Diffusion coefficient of cationic liposomes during lipoplex formation determines transfection efficiency in HepG2 cells

Cationic lipid-based lipoplexes are well-known for gene delivery. To determine the relationship between phys-icochemical characteristics and transfection efficiency, cationic liposomes of different sizes were prepared and incubated with plasmid DNA at different temperatures to form lipoplexes. We found that the liposome diffusion coefficient during lipoplex formation strongly correlated with the physicochemical characteristics of lipoplexes, accessibility of plasmid DNA in lipoplexes, and logarithm of gene expression per metabolic activity. Clathrin-mediated endocytosis was the major route for lipoplexes comprising 100 nm-liposomes, as reported previ-ously. As liposome size increased, the major route shifted to lipid raft-mediated endocytosis. In addition, mac-ropinocytosis was observed for all liposome sizes. The role of reactive oxygen species might depend on liposome size and endocytosis. Information from this study would be useful for understanding cationic lipoplex-mediated transfection.

Automated summary

Cationic lipid-based lipoplexes were prepared with different sizes and incubated with plasmid DNA at different temperatures to investigate the relationship between physicochemical characteristics and transfection efficiency. The diffusion coefficient of liposomes during lipoplex formation was found to strongly correlate with the physicochemical characteristics of lipoplexes, accessibility of plasmid DNA in lipoplexes, and gene expression per metabolic activity. Clathrin-mediated endocytosis was the major route for lipoplexes comprising 100 nm-liposomes, but as liposome size increased, the major route shifted to lipid raft-mediated endocytosis, with macropinocytosis observed for all liposome sizes. The role of reactive oxygen species may depend on liposome size and endocytosis. This study provides valuable information for understanding cationic lipoplex-mediated transfection.