pH-sensitive N,N-(dimethyl)-N-alkanamine-N-oxides as gene delivery vectors

N,N-(Dimethyl)-N-alkanamine-N-oxides C$_n$NO (n = 12 and 16) are amphiphiles that exist in neutral as well as in cationic forms depending on pH of aqueous solutions. C$_n$NO with a neutral lipid DOPE (dioleoylphosphatidylethanolamine) can form liposomes with positive surface charge in acidic pH solution. C$_n$NO/DOPE (n = 12 and 16) liposomes were used for preparation of DNA delivery vectors. Small-angle X-ray diffraction (SAXD) was used to determine the structure of C n NO/DOPE/DNA complexes prepared at various pH and 20 °C. At acidic pH, we observe a condensed lamellar phase L$^C$ with DNA strands packed regularly. With increasing pH, a coexistence of two lamellar phases is recognized. The amount of DNA bound into C$_n$NO/DOPE/DNA complexes shows significant dependence on pH as derived from UV/Vis spectroscopy. Up to ~99% of total DNA was complexed at acidic pH. The cytotoxicity of C$_{12}$NO/DOPE for HepG2 cells at acidic pH is low as determined by Janus Green Staining Assay

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