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New multivalent cationic lipids reveal bell curve for transfection efficiency versus membrane charge density: lipid-DNA complexes for gene delivery.

Authors :
Ahmad A
Evans HM
Ewert K
George CX
Samuel CE
Safinya CR
Source :
The journal of gene medicine [J Gene Med] 2005 Jun; Vol. 7 (6), pp. 739-48.
Publication Year :
2005

Abstract

Background: Gene carriers based on lipids or polymers-rather than on engineered viruses-constitute the latest technique for delivering genes into cells for gene therapy. Cationic liposome-DNA (CL-DNA) complexes have emerged as leading nonviral vectors in worldwide gene therapy clinical trials. To arrive at therapeutic dosages, however, their efficiency requires substantial further improvement.<br />Methods: Newly synthesized multivalent lipids (MVLs) enable control of headgroup charge and size. Complexes comprised of MVLs and DNA have been characterized by X-ray diffraction and ethidium bromide displacement assays. Their transfection efficiency (TE) in L-cells was measured with a luciferase assay.<br />Results: Plots of TE versus the membrane charge density (sigmaM, average charge/unit area of membrane) for the MVLs and monovalent 2,3-dioleyloxypropyltrimethylammonium chloride (DOTAP) merge onto a universal, bell-shaped curve. This bell curve leads to the identification of three distinct regimes, related to interactions between complexes and cells: at low sigmaM, TE increases with increasing sigmaM; at intermediate sigmaM, TE exhibits saturated behavior; and unexpectedly, at high sigmaM, TE decreases with increasing sigmaM.<br />Conclusions: Complexes with low sigmaM remain trapped in the endosome. In the high sigmaM regime, accessible for the first time with the new MVLs, complexes escape by overcoming a kinetic barrier to fusion with the endosomal membrane (activated fusion), yet they exhibit a reduced level of efficiency, presumably due to the inability of the DNA to dissociate from the highly charged membranes in the cytosol. The intermediate, optimal regime reflects a compromise between the opposing demands on sigmaM for endosomal escape and dissociation in the cytosol.<br /> (Copyright (c) 2005 John Wiley & Sons, Ltd.)

Details

Language :
English
ISSN :
1099-498X
Volume :
7
Issue :
6
Database :
MEDLINE
Journal :
The journal of gene medicine
Publication Type :
Academic Journal
Accession number :
15685706
Full Text :
https://doi.org/10.1002/jgm.717