Atomic force microscopy for studying gene transfection mediated by cationic liposomes with a cationic cholesterol derivative

Atomic force microscopy (AFM) was used for studying gene transfection mediated by cationic liposomes which contain a cationic cholesterol derivative with a different spacer arm, Cationic liposomes were made by a mixture of one of eight cationic cholesterol derivatives and 1,2-dioleoyl-sn-glycero-3-phosphatidyl ethanolamine (DOPE), AFM images showed that vesicles made of the liposome/DNA complex had various diameters depending on each cationic cholesterol derivative with a different spacer arm, The results showed that the diameter of the liposome/DNA complex was well related to the transfection activity of plasmid pSV2CAT DNA to a cultured cell line (NIH3T3), From the results it mas found that the vesicles with moderate diameters (from 0.4 to 1.4 mu m) mere moste effective for gene transfection of plasmid pSV2CAT DNA into the target cell, Neither smaller vesicles (< 400 nm) nor larger vesicles (> 1.4 mu m) were adequate for gene transfection, As the gene transfection by the cationic liposomes was mostly inhibited by wortmannin, an inhibitor of endocytosis, it is suggested that the vesicles with moderate diameters mere useful for gene transfection by endocytosis. (C) 1998 Federation of European Biochemical Societies.