Physical-Chemical Properties and Transfection Activity of Cationic Lipid/DNA Complexes (original) (raw)
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Interactions of Cationic Lipids with DNA: A Structural Approach
Langmuir
Colloidal nucleic acid carrier systems based on cationic lipids are a promising pharmaceutical tool in the implementation of gene therapeutic strategies. This study demonstrates the complex behavior of DNA at the lipid− solvent interface facilitating structural changes of the lyotropic liquid-crystalline phases. For this study, the structural properties of six malonic acid based cationic lipids were determined using small-and wide-angle X-ray scattering (SAXS and WAXS) as well as differential scanning calorimetry (DSC). Selected lipids (lipid 3 and lipid 6) with high nucleic acid transfer activity have been investigated in detail because of the strong influence of the zwitterionic helper lipid 1,2-di(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine (DOPE) on the structural properties as well as of the complex formation of lipid−DNA complexes (lipoplexes). In the case of lipid 3, DNA stabilizes a metastable cubic mesophase with Im3m symmetry and an Im3m Q α c lipoplex is formed, which is rarely described for DNA lipoplexes in literature. In the case of lipid 6, a cubic mesophase with Im3m symmetry turns into a fluid lamellar phase while mixing with DOPE and complexing DNA. 50 concerning over 30 cationic phospholipids. 1 The authors were 51 able to show that not only the simple adaption of the H II c 52 structure results in an efficient gene transfection 13,19 but also 53 the pathway into the cell and structural changes on this path 54 seem to be important. For example, lamellar lipoplexes work 55 very well if upon contact with (model) cell membranes a 56 lamellar to nonlamellar phase transition occurs. 1 In summary, 57 structural properties of lipids and lipoplexes cannot be related 58 to transfection rates in a straightforward manner for all cases. 59 Moreover, it is important to understand and explain each single 60 case in order to identify different promising structures and 61 mechanisms. 62 This work focuses on the physical−chemical characterization 63 f1 of six lipids designed for gene transfection (Figure 1). 64 Synthesis and transfection results are already described. 10 65 Lipids 1−3 and 4−6 possess different headgroups. The lipid 66 chains are either saturated or unsaturated. Lipids 1 and 2 are 67 not able to incorporate colipids and show no transfection 68 activity. 10 Lipids 3 and 6 are the most promising gene transfer 69 vehicles in complexes with noncharged colipids and DNA. The 70 mixtures of lipid 6 with DOPE 2:1 (n/n) and lipid 3 with 71 DOPE 1:2 (n/n) exhibit transfection efficiencies higher than
Modeling of Cationic Lipid-DNA Complexes
Current Medicinal Chemistry, 2004
Cationic lipid-DNA complexes, often referred to as lipoplexes, are formed spontaneously in aqueous solutions upon mixing DNA and liposomes composed of cationic and nonionic lipids. Understanding the mechanisms underlying lipoplex formation, structure and phase behavior is crucial for their further development and design as non-viral transfection vectors in gene therapy. From a physical point of view, lipoplexes are ordered, self-assembled, composite aggregates. Their preferred spatial geometry and phase behavior are governed by a delicate coupling between the electrostatic interactions which drive lipoplex formation and the elastic properties of the constituent lipid layers, both depending on the molecular nature and composition of the lipid mixture. In this review we outline some recent efforts to model the microscopic structure, energetics and phase behavior of cationic lipid-DNA mixtures, focusing on the two principal aggregation geometries: the lamellar (L C α ), or "sandwich" complexes, and the hexagonal (H C II ), or "honeycomb" complexes. We relate the structural and thermodynamic properties of these two "canonical" lipoplex morphologies to their appearance in phase diagrams of DNA-lipid mixtures, emphasizing the crucial role fulfilled by the molecular packing characteristics of the cationic and neutral lipids, as reflected in the curvature elastic properties of the mixed lipid layer. List of abbreviations: CL: cationic lipid DOPE: dioleoylphosphatidylethanolamine DOSPA: 2,3-dioleyloxy-N-[2(sperminecarboxamido)ethyl]-N,N-dimethyl-1-propanaminium trifluoroacetate ds: double stranded PC: phosphatidylcholine DOTAP 1,2-dioleoyl-3-(trimethyammonium) propane PE: phosphatidylethanolamine PB: Poisson-Boltzmann 1
DNA release from cationic liposome/DNA complexes by anionic lipids
Applied Physics Letters, 2006
The authors found that recently developed multicomponent cationic liposome DNA complexes ͑lipoplexes͒ exhibit higher transfection efficiency with respect to usually employed binary lipoplexes in NIH 3T3 and A17 cell lines. Interaction of lipoplexes with anionic liposomes ͑model of cellular membranes͒ was investigated by synchrotron small angle x-ray diffraction. The authors used one-dimensional DNA packing density to estimate the molar fraction of DNA released from lipoplexes by anionic lipids.
Cationic lipid–DNA complexes in gene delivery: from biophysics to biological applications
Advanced Drug Delivery Reviews, 2001
Great expectations from the application of gene therapy approaches to human disease have been impaired by the unsatisfactory clinical progress observed. Among others, the use of an efficient carrier for nucleic acid-based medicines is considered to be a determinant factor for the successful application of this promising therapeutic strategy. The drawbacks associated with the use of viral vectors, namely those related with safety problems, have prompted investigators to develop alternative methods for gene delivery, cationic lipid-based systems being the most representative. This review focuses on the various parameters that are considered to be crucial to optimize the use of cationic lipid-DNA complexes for gene therapy purposes. Particular emphasis is devoted to the analysis of the different stages involved in the transfection process, from the biophysical aspects underlying the formation of the complexes to the different biological barriers that need to be surpassed for gene expression to occur.
DNA-lipid systems: A physical chemistry study
Brazilian Journal of Medical and Biological Research, 2002
It is well known that the interaction of polyelectrolytes with oppositely charged surfactants leads to an associative phase separation; however, the phase behavior of DNA and oppositely charged surfactants is more strongly associative than observed in other systems. A precipitate is formed with very low amounts of surfactant and DNA. DNA compaction is a general phenomenon in the presence of multivalent ions and positively charged surfaces; because of the high charge density there are strong attractive ion correlation effects. Techniques like phase diagram determinations, fluorescence microscopy, and ellipsometry were used to study these systems. The interaction between DNA and catanionic mixtures (i.e., mixtures of cationic and anionic surfactants) was also investigated. We observed that DNA compacts and adsorbs onto the surface of positively charged vesicles, and that the addition of an anionic surfactant can release DNA back into solution from a compact globular complex between DNA and the cationic surfactant. Finally, DNA interactions with polycations, chitosans with different chain lengths, were studied by fluorescence microscopy, in vivo transfection assays and cryogenic transmission electron microscopy. The general conclusion is that a chitosan effective in promoting compaction is also efficient in transfection.
Langmuir, 2007
Cationic liposomes/DNA complexes can be used as nonviral vectors for direct delivery of DNA-based biopharmaceuticals to damaged cells and tissues. In order to obtain more effective and safer liposome-based gene transfection systems, the new cationic lipid 2-amino-3-hexadecyloxy-2-(hexadecyloxymethyl)propan-1-ol (AHHP) was synthesized. In this paper we report on the synthesis of AHHP and investigations of its physical-chemical properties. Langmuir monolayers of AHHP were studied at the air/buffer interface by film balance measurements, grazing incidence X-ray diffraction (GIXD), and infrared reflection absorption spectroscopy (IRRAS). Structure and thermotropic phase behavior of AHHP in aqueous dispersion were examined by small-angle and wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). The results show clear differences in structure and phase behavior of AHHP, both in the monolayer system and in aqueous dispersions, in dependence on the subphase pH due to protonation or deprotonation of the primary amine in the lipid head group. Thermodynamic data derived from π-A isotherms provide information about the critical temperature (T c), which is in rough agreement with the temperature of the lipid phase transition from gel to fluid state (T m) found by X-ray and calorimetry studies of AHHP aqueous dispersions. The packing properties of the molecules in mono-and bilayer systems are very similar. DNA couples to the monolayer of the new lipid at low as well as at high pH but in different amounts. The DNA coupling leads to an alignment of adsorbed DNA strands indicated by the appearance of a Bragg peak. The distance between aligned DNA strands does not change much with increasing monolayer pressure.
Journal of Medicinal Chemistry, 2002
Lipid-mediated delivery of DNA into cells holds great promise both for gene therapy and basic research applications. This paper describes the efficient and facile synthesis and the characterization of a new multivalent cationic lipid with a double-branched headgroup structure for gene delivery applications. The synthetic scheme can be extended to give cationic lipids of different charge, spacer, or lipid chain length. The chemical and physical properties of selfassembled complexes of the cationic liposomes (CLs) with DNA give indications of why multivalent cationic lipids possess superior transfection properties. The lipid bears a headgroup with five charges in the fully protonated state, which is attached to an unsaturated doublechain hydrophobic moiety based on 3,4-dihydroxybenzoic acid. Liposomes consisting of the new multivalent lipid and the neutral lipid 1,2-dioleoyl-sn-glycerophosphatidylcholine (DOPC) were used to prepare complexes with DNA. Investigations of the structures of these complexes by optical microscopy and small-angle X-ray scattering reveal a lamellar L R C phase of CL-DNA complexes with the DNA molecules sandwiched between bilayers of the lipids. Experiments using plasmid DNA containing the firefly luciferase reporter gene show that these complexes efficiently transfect mammalian cells. When compared to the monovalent cationic lipid 2,3dioleyloxypropyltrimethylammonium chloride (DOTAP), the higher charge density of the membranes of CL-DNA complexes achievable with the new multivalent lipid greatly increases transfection efficiency in the regime of small molar ratios of cationic to neutral lipid. This is desired to minimize the known toxicity effects of cationic lipids.
The encapsulation of DNA molecules within biomimetic lipid nanocapsules
Biomaterials, 2009
Most of DNA synthetic complexes result from the self-assembly of DNA molecules with cationic lipids or polymers in an aqueous controlled medium. However, injection of such self-assembled complexes in medium like blood that differ from that of their formulation leads to strong instability. Therefore, DNA vectors that have physico-chemical properties and structural organisation that will not be sensitive to a completely different medium in terms of ionic and protein composition are actively sought. To this end, the goal here was to discover and optimize a nanostructured system where DNA molecules would be encapsulated in nanocapsules consisting in an oily core and a shell covered by PEG stretches obtained through a nanoemulsion process in the absence of organic solvent. This encapsulation form of DNA molecules would prevent interactions with external hostile biological fluid. The results show the entrapment of lipoplexes into lipid nanocapsules, leading to the formation of neutral 110 nm-DNA nanocapsules. They were weakly removed by the immune system, displaying an increased blood half-life, and improved carcinoma cell transfection, in comparison to the parent lipoplexes. Our results demonstrate that the fabrication of nanocapsules encapsulating hydrophilic DNA in an oily core that meet criteria for blood injection is possible.