Enhancing Transfection Efficiency of Spermine-Based Cationic Lipids with a Lysine-Based Spacer

L-shape spermine-based cationic lipids with a lysine spacer and both identical and non-identical hydrophobic tails were successfully synthesized. Liposomes prepared from these lipids, either alone or in combination with DOPE, demonstrated DNA-binding capability, as confirmed by gel electrophoresis assays. The physicochemical properties, such as size, zeta-potential, and stability of the lipoplexes formed from the cationic lipids were investigated. The liposomes efficiently condensed DNA into compact structures at an N/P ratio of approximately 5–10. Interestingly, liposomes without DOPE exhibited higher transfection efficiency than those containing DOPE, with the cationic lipid featuring a spermine polar head bonded to a lysine spacer and C12–C16 hydrocarbon tails (Sper-Lys-C_12,16) achieved the greatest transfection efficiency, as revealed by fluorescence microscopy and flow cytometry. Notably, this formulation maintained high transfection efficiencies even in serum concentrations up to 40%, outperforming the commercial standard Lipofectamine 3000. Additionally, these liposomes exhibited low cytotoxicity, highlighting their potential as safe and effective gene delivery agents.