Effect of the preparation procedure on the structural properties of oligonucleotide/cationic liposome complexes (lipoplexes) studied by electron spin resonance and Zeta potential

Abstract

Lipoplexes with different surface charge were prepared from a short oligonucleotide (20 mer, dsAT) inserted into liposomes of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine (DOPE). The starting liposomes were prepared by two different procedures, i.e. progressive dsAT addition starting from plain liposomes (titration) and direct mixing of dsAT with pure liposomes (point to point preparation). Lipoplexes were characterized from a molecular point of view by Electron Spin Resonance (ESR) of a cationic spin probe and by Nuclear Magnetic Resonance. Structural and surface features were analysed by Zeta potential (zeta) measurements and Cryo-TEM micrographs. The complete set of results allowed to demonstrate that: i) the interactions between dsAT and cationic lipids were strong and occurred at the liposome surface; ii) the overall shape and physicochemical properties of liposomes did not change when short nucleic acid fragments were added before surface charge neutralization; iii) the bilayer structure of the lipids in lipoplexes was substantially preserved at all charge ratios; iv) the physical status of lipoplexes with electrical charge far from neutrality did not depend on the preparation method.

Dynamic Light Scattering Based Microelectrophoresis: Main Prospects and Limitations

“…[128] In fact, changes in the particle size and ζ potential in parallel are routinely followed to additionally support insights about the interaction of given entities, and a similar combinatorial principle could be applied with numerous other experimental techniques. Some of these methods that were used in combination with the DLS electrophoresis so as to gain more profound insights into the mechanisms of the investigated physicochemical transformations have been small angle x-ray scattering (SAXS), [129] circular dichroism (CD), [130] isothermal titration calorimetry, [131] microbalance, rheological, and conductivity analyzers, [132–137] flow fractionation technologies, [138] various infrared spectroscopies, [139,140] x-ray photoelectron spectroscopy, [141] nuclear magnetic resonance, [142] UV-vis spectroscopy, [143] electron spin resonance spectroscopy, [144] surface enhanced Raman spectroscopy, [145] a range of electron, optical, and atomic force microscopic techniques, [146–148] and many other. The main risk, however, is that the complemented methods may give contrasting and incompatible information.…”

Effect of Zeta Potential on the Properties of Nano-Drug Delivery Systems - A Review (Part 1)

“…The uptake of nanoparticles by cells can be viewed as a two step process: first, a binding step on the cell membrane and second, the internalization step [20]. The attachment of nanoparticles to cell membrane seems to be most affected by the surface charge of the particles [21][22].…”

Recent progress in gene therapy to deliver nucleic acids with multivalent cationic vectors

“…The gene vector is a mixture of a cationic lipid (CL), that yields the positive charge necessary to interact with both the negative nucleic acid and the cell membrane, and a helper lipid which works as coadyuvant of the transfection [34,[46][47][48][49][50][51].…”