A Columnar Phase of Dendritic Lipid−Based Cationic Liposome−DNA Complexes for Gene Delivery:  Hexagonally Ordered Cylindrical Micelles Embedded in a DNA Honeycomb Lattice

Abstract

Gene therapy holds great promise as a future approach to fighting disease and is explored in worldwide clinical trials. Cationic liposome (CL)-DNA complexes are a prevalent nonviral delivery vector, but their efficiency requires improvement and the understanding of their mechanism of action is incomplete. As part of our effort to investigate the structure-transfection efficiency relationships of self-assembled CL-DNA vectors, we have synthesized a new, highly charged (16+) multivalent cationic lipid, MVLBG2, with a dendritic headgroup. Our synthetic scheme allows facile variation of the headgroup charge and the spacer connecting hydrophobic and headgroup moieties as well as gram-scale synthesis. Complexes of DNA with mixtures of MVLBG2 and neutral 1,2-dioleoyl-sn-glycerophosphatidylcholine (DOPC) exhibit the well-known lamellar phase at 90 mol % DOPC. Starting at 20 mol % dendritic lipid, however, two novel nonlamellar phases are observed by synchrotron X-ray diffraction. The structure of one of these phases, present in a narrow range of composition around 25 mol % MVLBG2, has been solved. In this novel dual lattice structure, termed H(I)C, hexagonally arranged tubular lipid micelles are surrounded by DNA rods forming a three-dimensionally continuous substructure with honeycomb symmetry. Complexes in the H(I)C phase efficiently transfect mouse and human cells in culture. Their transfection efficiency, as well as that of the lamellar complexes containing only 10 mol% dendritic lipid, reaches and surpasses that of commercially available, optimized DOTAP-based complexes. In particular, complexes containing MVLBG2 are significantly more transfectant over the entire composition range in mouse embryonic fibroblasts, a cell line empirically known to be hard to transfect.

Real-Time Observation of Polyelectrolyte-Induced Binding of Charged Bilayers

“…For instance, in bioengineering, the interactions between lipids bilayers and DNA molecules are crucial for gene therapy. [28][29][30][31][32] When charged bilayers interact with polyelectrolyte of opposite charge, it is generally accepted that electrostatic interactions induce the bridging of the lipid bilayers by the PE molecules. [33][34][35] The resulting structure of the PE/lipid complexes is a condensed lamellar phase, with PE strands intercalated between the lipids bilayers.…”

Monitoring intracellular degradation of exogenous DNA using diffusion properties

“…Interestingly, the end-capping effect on the expression rate was different in the cell lines. In MEF cells, which are generally said to be hard to transfect [32], the end-capping effect was significant (Fig. 6E).…”

Optical, electro-optic and optoelectronic properties of natural and chemically modified DNAs

“…This chemistry is rapidly expanding the horizons of the materials science of DNA. The long alkyl groups tend to induce the formation of self-assembled three-dimensional architectures 14,15 through the hydrophobic interactions between them.…”