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 LC 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 C12NO/DOPE for HepG2 cells at acidic pH is low as determined by Janus Green Staining Assay.