Oxidisable cationic detergent for gene therapy: condensation of DNA and interaction with model membranes

Abstract

Cationic amphiphile-mediated delivery of plasmid DNA is the non-viral gene transfer method most often used. In the present work, we considered a new cysteine-detergent, ornithinyl-cysteinyl-tetradecylamide (C₁4-CO), able to convert itself, via oxidative dimerisation, into a cationic cystine-lipid. By using fluorescence techniques, we first characterised the structure of complexes of plasmid DNA with C₁4-CO molecules either kept as monomers, or oxidised into dimers. Both forms are able to condense DNA, with the formation of hydrophobic micelle-like domains along the DNA chain. Domains with a larger molecular order were obtained with dimeric C₁4-CO/DNA complexes. In a second step, the interactions of these complexes with lipid vesicles considered as membrane models were investigated. In the presence of vesicles, we observed a decondensation of the DNA involved in complexes obtained with C₁4-CO monomers. With anionic vesicles, the DNA is released into the bulk solution, while with neutral vesicles, it remains bound to the vesicles via electrostatic interactions with inserted C₁4-CO molecules. In sharp contrast, the complexes with C₁4-CO dimers are unaffected by the addition of either neutral or anionic vesicles and show no interaction with them. These results may partly explain the low transfection efficiency of these complexes at the +/− charge ratios used in this study.

Acknowledgements This work was supported by ARC, Ligue Régionale du Bas-Rhin et du Haut-Rhin contre le Cancer, and FRM. D.L., J-P.C. and E.D. are recipient of doctoral fellowships from MENRT, the Ligue Régionale du Bas-Rhin et du Haut-Rhin contre le cancer and AFLM, respectively.