Counterion Effects on Properties of Cationic Vesicles

Abstract

The effect of counterion nature and concentration on phase transition, bilayer structure, vesicle size, vesicle internal volume per mole of amphiphile, and surface potential is evaluated for cationic vesicles composed of dioctadecyldimethylammonium (DODA) acetate, chloride, or bromide. Over a range of ionic strengths (0−5 mM monovalent salt), no interdigitation was detected in the bilayer structure for the three DODA counterions. The preferential type of aggregate formed from self-assembly of DODA salts is a large vesicle composed of a single traditional and noninterdigitated bilayer. Vesicle size and zeta-potentials were inversely related, i.e., an increase in zeta-potential was accompanied by a decrease in vesicle size. The largest zeta-potentials and smallest sizes were obtained for bilayer vesicles of DODA acetate which have the largest and more hydrated counterion. The effect of ionic strength (0−5 mM NaAc, NaCl, or NaBr as monovalent salt) was a slight decrease followed by a significant increase in vesicle size as a function of salt concentration. The results for counterion effects on vesicle size agree with predictions from the self-assembly model by Israelachvili and co-workers.

Spontaneous Vesicles Modulated by Polymers

“…When the PMAO concentration is further increased the ζ-potential weakly decreases. This fact agrees very well with results obtained by other authors [49,50]. In these works, the combination of light scattering and ζ-potential measurements indicated that the zeta-potential often decreases with increasing the vesicle radius.…”

“…One of the most interesting results found was that mixed vesicles of Aerosol OT and poly(allylamine) become unstable when the electric charge of vesicles is not completely neutralized. This behavior was interpreted using the Volegol's [50,51] model. This model considers that the non-uniform distribution on the surface electric charge due to the highly correlated adsorption of the polyelectrolyte on the vesicle surfaces induces attractive interactions between vesicles that finally flocculate even though the surface charge of vesicles is not completely neutralized.…”

Development of Dioctadecyldimethylammonium Bromide/Monoolein Liposomes for Gene Delivery

“…DODAB is a bilayer-forming cationic lipid that tends to form large unilamellar vesicles (LUV's) in excess water [47,48]. It features a hydrophobic moiety consisting of a double acyl chain (C18:0) attached to a quaternary ammonium headgroup (one single positive charge per molecule) [49,50].…”

Assembly of horseradish peroxidase within supported cationic bilayers

“…Small DODAB BF, (73 AE 1) nm mean diameter and (45 AE 3) mV mean zeta-potential were prepared above the mean phase transition temperature of the DODAB bilayer (45 C) 25 by probe sonication (80-90 mW, 10 min, above 70 C) in 1 mM NaCl Milli-Q water solution at ca., 2.0 mM DODAB as previously described. 18 The sonicated dispersion was centrifuged at 10,000 g/15 C /40 min, to eliminate titanium residues ejected from the tip.…”