Structural Characteristics of Supramolecular Assemblies Formed by Guanidinium-Cholesterol Reagents for Gene Transfection

• Published in: Proceedings of the National Academy of Sciences - PNAS 1999-03, Vol.96 (6), p.2621-2626
• Main Authors: Pitard, Bruno, Oudrhiri, Noufissa, Vigneron, Jean-Pierre, Hauchecorne, Michelle, Aguerre, Olivier, Toury, Renée, Airiau, Marc, Ramasawmy, Rajen, Scherman, Daniel, Crouzet, Joël, Lehn, Jean-Marie, Lehn, Pierre
• Format: Article
• Language: English
• Subjects: Biological Sciences; Cell aggregates; Cholesterol; Cholesterol - chemistry; DNA - chemistry; DNA - ultrastructure; Endosomes; Fluorescence; Gene Transfer Techniques; Genes; Genetic Vectors - chemistry; Genetic Vectors - ultrastructure; Guanidine - chemistry; HeLa Cells; Humans; Lipids; Liposomes; Microscopy, Electron; Molecular biology; Plasmids; Reagents; Transfection; X-Ray Diffraction
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.96.6.2621

We have recently discovered that cationic cholesterol derivatives characterized by guanidinium polar headgroups are very efficient for gene transfection in vitro and in vivo. In spite of being based on some rationale at the molecular level, the development of these new synthetic vectors was nevertheless empirical. Indeed, the factors and processes underlying cationic lipid-mediated gene transfer are still poorly understood. Thus, to get a better insight into the mechanisms involved, we have examined the supramolecular structure of lipid/DNA aggregates obtained when using reagent bis(guanidinium)-tren-cholesterol (BGTC), either alone or as a liposomal formulation with the neutral phospholipid dioleoyl phosphatidylethanolamine (DOPE). We here report the results of cryotransmission electron microscopy studies and small-angle x-ray scattering experiments, indicating the presence of multilamellar domains with a regular spacing of 70 angstrom and 68 angstrom in BGTC/DOPE-DNA and BGTC-DNA aggregates, respectively. In addition, DNA lipoplexes with similar lamellar patterns were detected inside transfected HeLa cells by conventional transmission electron microscopy. These results suggest that DNA condensation by multivalent guanidinium-cholesterol cationic lipids involves the formation of highly ordered multilamellar domains, the DNA molecules being intercalated between the lipid bilayers. These results also invite further investigation of the intracellular fate of the internalized lipid/DNA structures during their trafficking toward the cell nucleus. The identification of the basic features of active complexes should indeed help in the design of improved guanidinium-based vectors.