Molecular Shape of the Cationic Lipid Controls the Structure of Cationic Lipid/Dioleylphosphatidylethanolamine-DNA Complexes and the Efficiency of Gene Delivery

Abstract

Pyridinium amphiphiles, abbreviated as SAINT, are highly efficient vectors for delivery of DNA into cells. Within a group of structurally related compounds that differ in transfection capacity, we have investigated the role of the shape and structure of the pyridinium molecule on the stability of bilayers formed from a given SAINT and dioleoylphosphatidylethanolamine (DOPE) and on the polymorphism of SAINT/DOPE-DNA complexes. Using electron microscopy and small angle x-ray scattering, a relationship was established between the structure, stability, and morphology of the lipoplexes and their transfection efficiency. The structure with the lowest ratio of the cross-sectional area occupied by polar over hydrophobic domains (SAINT-2) formed the most unstable bilayers when mixed with DOPE and tended to convert into the hexagonal structure. In SAINT-2-containing lipoplexes, a hexagonal topology was apparent, provided that DOPE was present and complex assembly occurred in 150 mM NaCl. If not, a lamellar phase was obtained, as for lipoplexes prepared from geometrically more balanced SAINT structures. The hexagonal topology strongly promotes transfection efficiency, whereas a strongly reduced activity is seen for complexes displaying the lamellar topology. We conclude that in the DOPE-containing complexes the molecular shape and the nonbilayer preferences of the cationic lipid control the topology of the lipoplex and thereby the transfection efficiency.

Development of Dioctadecyldimethylammonium Bromide/Monoolein Liposomes for Gene Delivery

“…DOPE stimulates the formation of inverted hexagonal structures (HII - Fig 3A) which represent a major structural variation from the classic multilamellar sandwich model of lipoplex organization (Lα C - Fig. 3B) [80]. However, its application in gene therapy has been strongly limited because of the strong cytotoxicity associated with it [81,82].…”

Transferrin-Associated Lipoplexes as Gene Delivery Systems: Relevance of Mode of Preparation and Biophysical Properties

“…Formation of inverted hexagonal structures: The capacity of the lipid incorporated in lipoplexes to form inverted hexagonal structures (H II ) in the endosome has been reported to favor transfection by facilitating endosomal escape of DNA (Shi et al, 2002;Zuhorn et al, 2002Zuhorn et al, , 2005. It has been reported that the ionic strength of the medium has a dramatic effect on the phase behavior of the lipids in the complexes (Scarzello et al, 2005;Shi et al, 2002;Smisterova et al, 2001). In this regard, the presence of NaCl in the medium may contribute to a reduction of the cross-sectional headgroup area, thus favoring the formation of H II phases.…”

Serum-free transfection of CHO-cells with tailor-made unilamellar vesicles

“…Especially the inverted hexagonal phase shows high transfection efficiencies (Boomer and Thompson 1999;Rejman et al 2005). A close correlation could be found between the occurrence of a lamellar to inverted hexagonal phase transition and the presence of helper lipids like DOPE (Smisterova et al 2001) which strongly promotes formation of such inverted lipid structures (Lohner 1996). Therefore, cationic lipids in combination with DOPE represent attractive DNA vehicles.…”