Characterization of the Nanostructure of Complexes Formed by a Redox-Active Cationic Lipid and DNA

Abstract

We report characterization of the nanostructures of complexes formed between the redox-active lipid bis(n-ferrocenylundecyl)dimethylammonium bromide (BFDMA) and DNA using small-angle neutron scattering (SANS) and cryogenic transmission electron microscopy (cryo-TEM). A particular focus was directed to the influence of lipid oxidation state (where reduced BFDMA has a net charge of +1 and oxidized BFDMA has a charge of +3) on the nanostructures of the solution aggregates formed. Complexes were characterized over a range of charge ratios of reduced BFDMA to DNA (1.1:1, 2.75:1, and 4:1) in solutions of 1 mM Li2SO4. For these complexes, a single peak in the SANS data at 1.2 nm(-1) indicated that a nanostructure with a periodicity of 5.2 nm was present, similar to that observed with complexes of the classical lipids DODAB/DOPE and DNA (multilamellar spacing of 7.0 nm). The absence of additional Bragg peaks in all the SANS data indicated that the periodicity did not extend over large distances. Both inverse Fourier transform analysis and form factor fitting suggested formation of a multilamellar vesicle. These results were confirmed by cryo-TEM images in which multilamellar complexes with diameters between 50 and 150 nm were observed with no more than seven lamellae per aggregate. In contrast to complexes of reduced BFDMA and DNA, Bragg peaks were absent in SANS spectra of complexes formed by oxidized BFDMA and DNA at all charge ratios investigated. The low-q behavior of the SANS data obtained using oxidized BFDMA and DNA complexes suggested that large, loose aggregates were formed, consistent with complementary cryo-TEM images showing predominantly loose disordered aggregates. Some highly ordered spongelike and cubic phase nanostructures were also detected in cryo-TEM images. We conclude that control of BFDMA oxidation state can be used to manipulate the nanostructures of lipid-DNA complexes formed using BFDMA.

Dilution induced thickening in hydrotrope-rich rod-like micelles

“…These fluctuations smear out at large distances indicating that the periodicity associated with these nanostructures does not extend over large distances. SANS studies on lipid-DNA complex particles with multilamellar internal structure showed periodic oscillations in the PDDF [40]. The q À2 behavior observed in the low q-region of SANS data from sample at / = 0.006 is characteristic of a bilayer structure.…”

Addition of ascorbic acid to the extracellular environment activates lipoplexes of a ferrocenyl lipid and promotes cell transfection

“…The samples were contained in quartz cells with a 2 mm path length and placed in a sample chamber held at 25.0 ± 0.1 °C. The data were corrected for detector efficiency, background radiation, empty cell scattering, and incoherent scattering to determine the intensity on an absolute scale [40]. The background scattering from the solvent was subtracted.…”

“…This lipid can be reversibly cycled between its reduced state (net charge of +1) and its oxidized state (net charge of +3) by either oxidation or reduction of the ferrocene groups present at the end of each hydrophobic chain [35–41]. Our past studies have demonstrated that the oxidation state of BFDMA significantly affects the interaction of this lipid with DNA [39, 40] and the efficiency with which lipoplexes of BFDMA and DNA transfect cells [37, 38, 41]. In particular, our past studies have identified a range of lipid concentrations over which lipoplexes formed from reduced BFDMA mediate high levels of transgene expression in vitro , whereas lipoplexes formed from oxidized BFDMA (over the same range of concentrations) yield negligible levels of transgene expression [37, 38, 41].…”

“…In particular, our past studies have identified a range of lipid concentrations over which lipoplexes formed from reduced BFDMA mediate high levels of transgene expression in vitro , whereas lipoplexes formed from oxidized BFDMA (over the same range of concentrations) yield negligible levels of transgene expression [37, 38, 41]. Our previous physical characterization experiments also reveal that the oxidation state of BFDMA influences the zeta potentials and nanostructures of lipoplexes formed from BFDMA [39, 40]. …”

Control of Dual Stimuli-Responsive Vesicle Formation in Aqueous Solutions of Single-Tailed Ferrocenyl Surfactant by Varying pH and Redox Conditions

“…Dodecyltrimethylammonium bromide DTAB was added to the dilute solutions to eliminate cloudy solutions of 11-FAB 29,30 . DTAB does not absorb visible light wavelength 400-700 nm .…”