Physical properties of liposomes. Liposome size (A), loading efficiency of DOX (B), and zeta potential of the liposomal surface (C). Control represents DSPE liposomes. PEI-1, PEI-2, PEI-3, and PEI-4 represent PEI contents of 10%, 40%, 70%, and 100% (w/w total lipid) in liposomal formulations, respectively. Data shown represent means ± SD (n = 3).