Interaction Of Lipoplexes Research Articles

A DSC investigation on the influence of gemini surfactant stereochemistry on the organization of lipoplexes and on their interaction with model membranes

Previous investigations showed that the extent of DNA condensation and the efficiency in the transfection of liposomes formulated with 1,2-dimyristoyl-sn-glycero-phosphocholine and cationic stereomeric gemini surfactants depend heavily on the stereochemistry of the gemini. The influence of the stereochemistry on the interaction of lipoplexes with zwitterionic and anionic cell membrane models was investigated by differential scanning calorimetry to rationalize their different biological behavior. Further, the thermotropic behavior of the corresponding liposomes and of the spontaneous self-assemblies of gemini surfactants in the presence and in the absence of DNA was evaluated to correlate the physicochemical properties of lipoplexes and the stereochemistry of the cationic component. The obtained results show that the stereochemistry of the gemini surfactant controls lipoplexes organization and their mode and kinetic of interaction with different cell membrane models.

Interaction of Cationic Lipoplexes with Floating Bilayers at the Solid−Liquid Interface

Neutron reflection has been used to study the interaction of cationic lipoplexes with different model membrane systems. The model membranes used are prepared as "floating" phospholipid bilayers deposited at a silicon/water interface and separated from the solid substrate either by an adsorbed phospholipid bilayer, polymer cushions composed of polyethylene glycol lipids, or a lipid monolayer adsorbed onto a chemically grafted hydrocarbon layer. The cationic lipoplexes studied are those formed by the complexation of calf thymus DNA with dimethyl-dioctadecylammonium bromide (DDAB), with either cholesterol or dioleoyl-L-alpha-phosphatidylethanolamine (DOPE) incorporated as "helper" lipid. The cationic lipoplexes are found to destroy three of the four types of (negatively charged) floating bilayers, with the rate of destruction dependent on the nature of the layer separating the floating bilayer from the silicon substrate. The only bilayers to remain intact after exposure to the lipoplexes were those fabricated above the chemically grafted (octadecyl) hydrocarbon layer. This supports the hypothesis that the high negative charge density of the SiO2 layer on the silicon surface may influence, by way of electrostatic interaction with the cationic lipid, the interaction of the lipoplexes with the model bilayer. It is concluded that the floating bilayer supported on a chemically grafted hydrocarbon layer lends itself perfectly to the study of lipoplex-membrane interactions and, with sufficient exposure time, would allow a detailed characterization of the structures formed at the membrane interface during the interaction.

Interaction of Lipoplexes with Anionic Lipids Resulting in DNA Release is a Two-Stage Process

We propose a mechanism for DNA release from lipoplexes in cells that accounts for various observations of lipoplex-anionic lipid interactions. We examined the structural evolution of lipoplexes upon interaction with cellular lipids by synchrotron small-angle X-ray diffraction (SAXD), and the extent of DNA release from lipoplexes was determined by gel electrophoresis. We find that the interaction of lipoplexes with anionic cellular lipids is a two-stage process. In the first step, anionic lipids laterally diffuse into the complex and neutralize the cationic lipids. As a result, the membrane charge density of lipoplexes decreases and interactions between cationic lipids and DNA become weaker, but DNA is extremely poorly released. Only after the cationic charge of lipoplex membranes is completely neutralized by anionic lipids does DNA starts to be released significantly.

DNA release from cationic liposome/DNA complexes by anionic lipids

The authors found that recently developed multicomponent cationic liposome DNA complexes (lipoplexes) 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 membranes) 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.

Lipoplex-induced hemagglutination: potential involvement in intravenous gene delivery.

We report a study aiming to characterize the interaction of blood and blood components with lipoplexes under conditions relevant to in vivo intravenous transfection. In this study we focus on the interaction of lipoplexes with red blood cells (RBC). It was found that no significant hemolysis occurred during several hours' incubation using lipoplex compositions and lipoplex/red blood cell ratios in the range commonly used for in vivo transfection. However, the interaction of RBC with lipoplexes resulted in massive agglutination, which occurs irrespective of the type of cationic lipid or helper lipid. Agglutination was also induced by polyplexes (such as dendrimer/DNA complexes) and lipoplexes in the presence of spermidine or protamine sulfate (the latter induced hemagglutination by itself). DSPE-PEG(2000) inserted into the lipoplexes inhibits hemagglutination somewhat. In order to understand the effect of serum on the agglutination better, plasma was separated into its high molecular weight components (HMWC, >14 kDa) and its low molecular weight components (LMWC, < or = 14 kDa). These fractions were characterized for their level of proteins, primary amino groups, osmotic pressure, and electrical conductivity, and compared with saline (0.15 M NaCl). It was found that both LMWC and HMWC inhibit agglutination by themselves, although whole serum demonstrates better hemagglutination inhibition than each fraction separately. The inhibitory effect of the serum (or plasma) is explained by its effect on the electrostatics of the lipoplexes, reducing their positive charge, as was demonstrated using fluorescein-phosphatidylethanolamine-labeled lipoplexes. The effect of LMWC was related to ionic strength and was equal to the effect of 0.15 M NaCl. The level of agglutination was reduced with increasing lipoplex DNA(-)/cationic lipid(+) (DNA(-)/L(+)) ratio. However, at the low DNA(-)/L(+) ratio needed to achieve significant in vivo transfection after i.v. administration, massive agglutination occurred. These data suggest that i.v. administration of lipoplexes and polyplexes may lead to RBC agglutination, and the agglutinates formed may explain the localization of lipoplexes and expression of their transgenes in the lungs.