Varying the unsaturation in N⁴,N⁹-dioctadecanoyl spermines: Nonviral lipopolyamine vectors for more efficient plasmid DNA formulation

Purpose: The aim of the study is to analyze the effect of varying the degree of unsaturation in synthesized N4,N9-dioctadecanoyl spermines on DNA condensation and then to compare their transfection efficiency in cell culture.
Methods: The N4,N9-di-C18 lipopolyamines—saturated (stearoyl), C9-cis- (oleoyl), and C9,12-di-cis- (linoleoyl)—were synthesized from the naturally occurring polyamine spermine. The ability of these novel compounds to condense DNA and form nanoparticles was studied using ethidium bromide fluorescence quenching and nanoparticle characterization techniques. Transfection efficiency was studied in several primary skin cells (FEK4, FCP4, FCP5, FCP7, and FCP8) and in an immortalized cancer cell line (HtTA) and was compared with the commercially available nonliposomal transfection formulation Transfectam® (dioctadecylamidoglycyl spermine), which also contains two saturated C18 lipid chains.
Results: N4,N9-Dilinoleoyl spermine (C18, di-cis-9,12) is efficient at circular plasmid DNA (pEGFP) condensation and gives the most effective transfection in a series of primary skin cells and cancer cell lines at low charge ratios of 5.5 (± ammonium/phosphate).
Conclusions: The dienoic fatty acyl spermine conjugate N4,N9-dilinoleoyl spermine efficiently condenses DNA and achieves the highest transfection levels among the studied lipopolyamines in cultured cells.