DNA-DOPE-gemini surfactants complexes at low surface charge density: from structure to transfection efficiency.

DNA condensation, structure and transfection efficiency of complexes formed by gemini surfactants alkane-α,ω-diyl-bis(dodecyldimethylammonium bromide)s (CnGS12, n = 3, 6 and 12 is the number of alkane spacer carbons), dioleoylphosphatidylethanolamine (CnGS12/DOPE = 0.3 mol/mol) and DNA at low surface charge density were investigated through different techniques. Small angle X-ray diffraction showed a condensed lamellar phase with marked dependence of DNA-DNA distance on (+/-) charge ratio. High ionic strength of hydrating medium screens the interaction DNA - CnGS12/DOPE and complexed DNA represented maximally ~ 45-60% of total DNA in the solution as derived from fluorescence and UV-VIS spectroscopy. The in vitro transfection efficiency of CnGS12/DOPE liposomes on mammalian HEK 293 cell line was spacer length-dependent. C12GS12/DOPE/DNA complexes exhibited the best transfection efficiency (~ 18% GFP-expressing cells relative to all viable cells) accompanied by ~ 89% cell viability.