An Inverted Hexagonal Phase of Cationic Liposome-DNA Complexes Related to DNA Release and Delivery

Koltover, Ilya; Salditt, Tim; Rädler, Joachim O.; Safinya, Cyrus R.

doi:10.1126/science.281.5373.78

Cited by 1,236 publications

(1,309 citation statements)

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“…The sequence of events outlined above leads to a strong electrostatic attraction. This type of electrostatic interaction has been observed for self-assembled complexes between membranes and a variety of anionic polymers, including DNA [64][65][66], F-actin [67], microtubules [68], and filamentous phages [69].…”

Section: Electrostaticsmentioning

confidence: 77%

Arginine‐rich cell‐penetrating peptides

et al. 2009

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a b s t r a c tArginine-rich cell-penetrating peptides are short cationic peptides capable of traversing the plasma membranes of eukaryotic cells. While successful intracellular delivery of many biologically active macromolecules has been accomplished using these peptides, their mechanisms of cell entry are still under investigation. Recent dialogue has centered on a debate over the roles that direct translocation and endocytotic pathways play in internalization of cell-penetrating peptides. In this paper, we review the evidence for the broad range of proposed mechanisms, and show that each distinct process requires negative Gaussian membrane curvature as a necessary condition. Generation of negative Gaussian curvature by cell-penetrating peptides is directly related to their arginine content. We illustrate these concepts using HIV TAT as an example.

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Section: Electrostaticsmentioning

confidence: 77%

Arginine‐rich cell‐penetrating peptides

et al. 2009

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“…The left-handed chirality exhibited by these toroidally-packed bundles and indicated by the negative ellipticities, results from the DNA right-handed secondary conformations, as discussed above. The proposed structure provides a straightforward interpretation of the spectral features, as well as of the di¡erential interference contrast images of the complexes, where connected blobs were detected [5]. Moreover, the attenuation of the i-CD signal at high DOTAP/DNA ratio can be directly assigned to a more extensive coverage of the DNA by the lipids which negates a lipid-free DNA collapse.…”

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confidence: 93%

Chiral DNA packaging in DNA‐cationic liposome assemblies

1999

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Recent studies have indicated that the structural features of DNA-lipid assemblies, dictated by the lipid composition and cationic lipid-to-DNA ratio, critically affect the efficiency of these complexes in acting as vehicles for cellular delivery of genetic material. Using circular dichroism we find that upon binding DNA, positively-charged liposomes induce a secondary conformational transition of the DNA molecules from the native B form to the C motif. Liposomes composed of positively-charged and neutral`helper' lipids, found to be particularly effective as transfecting agents, induce^in addition to secondary conformational changes^DNA condensation into a left-handed cholesteric-like phase. A structural model is presented according to which two distinct, yet inter-related modes of DNA packaging coexist within such assemblies. The results underline the notion that subtle changes in the components of a supramolecular assembly may substantially modulate the interplay of interactions which dictate its structure and functional properties.z 1999 Federation of European Biochemical Societies.Key words: Chiral DNA packaging; DNA-cationic liposome assemblies DNA-cationic liposome assemblies became the subject of intensive studies due to their unique properties and their high e¤ciency in acting as vehicles for DNA delivery into eukaryotic cells [1]. Two inter-related processes were shown to occur upon interaction between positively-charged liposomes and DNA: a DNA-induced membrane fusion and a liposome-mediated DNA condensation [2]. High resolution studies indicated the formation of DNA-lipid complexes whose lamellar [3,4] or columnar inverted-hexagonal [5,6] structures depend upon the lipid composition and the cationic lipid-to-DNA ratio. Intriguingly, the columnar inverted-hexagonal complexes, obtained when the cationic liposomes contain the neutral helper lipid dioleoyl-phosphatidylethanolamine (DOPE), were found to be particularly e¡ective as transfecting agents [5]. This may be related to the fact that DOPE introduces: better matching in charge density [8] between lipid and DNA surfaces, easier counter-ion release of the lipid surface by the DNA [7], lower hydration of the lipid surface (Hirsch-Lerner and Barenholz, unpublished). These DOPE e¡ects prompted us to examine the conformational modulations exhibited by DNA molecules upon their binding to liposomes composed of the cationic dioleoyl-trimethylammonium-propane (DOTAP) in the presence and absence of DOPE.We ¢nd that DNA molecules bound to liposomes containing pure DOTAP sustain a B-to-C secondary conformational change, whereas the presence of DOPE induces both secondary and tertiary DNA transitions. Signi¢cantly, DOTAP-DOPE liposomes a¡ect DNA collapse into a tightly-packed phase characterized by a long-range chiral order. Circular dichroism (CD) studies were conducted on DNAliposome complexes at various lipid compositions and lipidto-DNA ratios (Fig. 1). In the absence of cationic lipids, supercoiled plasmid DNA molecules exhibit short-wave negative a...

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“…X-ray diffraction experiments have revealed several liquid crystalline phases of CL-DNA complexes. The two most prominent structures are: (i) a lamellar phase (L C α ), with 2D smectic array of DNA within lipid bilayers [8], and (ii) an inverted hexagonal phase (H C II ), where the DNA rods are packed in hexagonal lattice and the lipids form monolayers around them [9].Isoelectric complexes, where the total charge on the DNA molecules exactly matches the total charge of the CLs, are the most stable ones because they enable nearly complete counterion release [12]. The thermodynamic stability of a lipoplex, however, is only one of several biophysical parameters affecting the TEs of lipoplexes.…”

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confidence: 99%

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confidence: 99%

The thermodynamics of endosomal escape and DNA release from lipoplexes

Avital

Grønbech‐Jensen

Farago

2016

Phys. Chem. Chem. Phys.

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Complexes of cationic and neutral lipids and DNA (lipoplexes) are emerging as promising vectors for gene therapy applications. Their appeal stems from their non pathogenic nature and the fact that they self-assemble under conditions of thermal equilibrium. Lipoplex adhesion to the cell plasma membrane initiates a three-stage process termed transfection, consisting of (i) endocytosis, (ii) lipoplex breakdown, and (iii) DNA release followed by gene expression. As successful transfection requires lipoplex degradation, it tends to be hindered by the lipoplex thermodynamic stability; nevertheless, it is known that the transfection process may proceed spontaneously. Here, we use a simple model to study the thermodynamic driving forces governing transfection. We demonstrate that after endocytosis [stage (i)], the lipoplex becomes inherently unstable. This instability, which is triggered by interactions between the cationic lipids of the lipoplex and the anionic lipids of the enveloping plasma membrane, is entropically controlled involving both remixing of the lipids and counterions release. Our detailed calculation shows that the free energy gain during stage (ii) is approximately linear in Φ+, the mole fraction of cationic lipids in the lipoplex. This free energy gain, ∆F , reduces the barrier for fusion between the enveloping and the lipoplex bilayers, which produces a hole allowing for DNA release [stage (iii)]. The linear relationship between ∆F and the fraction of cationic lipids explains the experimentally observed exponential increase of transfection efficiency with Φ+ in lamellar lipoplexes.Somatic gene therapy holds great promise for future medical applications including, for example, new treatments for various inherited diseases and cancers [1]. Within this approach, an attempt is made to replace damaged genes with properly functioning ones. The core of the process, called transfection, includes the key steps of transferring foreign DNA into a target cell, followed by expression of the genetic information. Complexes composed of cationic lipids (CLs) and DNA, designated lipoplexes, constitute one of the most promising non-viral gene delivery systems [2][3][4]. Though their transfection efficiency (TE) is, in general, inferior to that of viral vectors, lipoplexes have the advantage of triggering low immune response, and being non-pathogenic [4][5][6][7]. Furthermore, lipoplexes allow transfer of larger DNA segments. Their production does not require sophisticated engineering, since they form spontaneously in aqueous solutions when DNA molecules are mixed with CLs and neutral lipids (NLs) [8][9][10][11]. The main thermodynamic driving force for lipoplex formation is the entropic gain stemming from the release of the tightly bound counterions from the DNA and the lipid bilayers. X-ray diffraction experiments have revealed several liquid crystalline phases of CL-DNA complexes. The two most prominent structures are: (i) a lamellar phase (L C α ), with 2D smectic array of DNA within lipid bilayers [8], and (ii) an i...

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An Inverted Hexagonal Phase of Cationic Liposome-DNA Complexes Related to DNA Release and Delivery

Cited by 1,236 publications

References 23 publications

Arginine‐rich cell‐penetrating peptides

Arginine‐rich cell‐penetrating peptides

Chiral DNA packaging in DNA‐cationic liposome assemblies

The thermodynamics of endosomal escape and DNA release from lipoplexes

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