Spontaneous Self-Assembly of Thermoresponsive Vesicles Using a Zwitterionic and an Anionic Surfactant

Abstract

Spontaneous formation of vesicles from the selfassembly of two specific surfactants, one zwitterionic (oleyl amidopropyl betaine, OAPB) and the other anionic (Aerosol-OT, AOT), is explored in water using small-angle scattering techniques. Two factors were found to be critical in the formation of vesicles: surfactant ratio, as AOT concentrations less than equimolar with OAPB result in cylindrical micelles or mixtures of micellar structures, and salt concentration, whereby increasing the amount of NaCl promotes vesicle formation by reducing headgroup repulsions. Small-angle neutron scattering measurements reveal that the vesicles are approximately 30−40 nm in diameter, depending on sample composition. Small-angle X-ray scattering measurements suggest preferential partitioning of OAPB molecules on the vesicle inner layer to support vesicular packing. Heating the vesicles to physiological temperature (37 °C) causes them to collapse into smaller ellipsoidal micelles (2−3 nm), with higher salt concentrations (≥10 mM) inhibiting this transition. These aggregates could serve as responsive carriers for loading or unloading of aqueous cargoes such as drugs and pharmaceuticals, with temperature changes serving as a simple release/uptake mechanism.

Morphology of bile salts micelles and mixed micelles with lipolysis products, from scattering techniques and atomistic simulations

“…Interestingly, the evolution of the scattering curves (Figure 11) is reminiscent of mixtures of the zwitterionic surfactant oleyl amidopropyl betaine with AOT (an anionic surfactant) and NaCl, recently reported [94]; upon reducing salt content, the curves show a similar structural evolution, which was analysed with a model comprising a mixture of vesicles with ellipsoidal/cylindrical micellar aggregates.…”

Enhanced Sunscreen Effects via Layer-By-Layer Self-Assembly of Chitosan/Sodium Alginate/Calcium Chloride/EHA

“…Due to its mechanism that was deposited oppositely charged polyelectrolytes with the interaction of electrostatic interaction, thus the morphology [ 12 ], size and other properties of the nanocapsules could be controlled by adjusted the number of assembly layers [ 13 ]. Unlike other methods, the nanocapsules prepared by LBL technology could be adjusted according to demands, such as controlled the diffusion rate by adjusted the thickness of wall, changed the shape by adjusted the pH and ionic strength of solutions, prepared multi component composite shell by used many kinds of materials [ 14 ]. However, it was necessary to prepare more than ten layers to construct the stable capsule [ 15 ].…”

A Critical Review of the Use of Surfactant-Coated Nanoparticles in Nanomedicine and Food Nanotechnology

“…For example, anionic surfactant (sodium bis(2-ethylhexyl) sulfosuccinate [AOT], which self-assembles into the shape of ellipsoidal micelles), forms vesicles in the presence of zwitterionic surfactant (oleyl amidopropyl betaine [OAPB], which self-assembles into the shape of worm-like micelles [Figure 1]) and salt. 13 Zwitterionic surfactant (3-[N,N-dimethyltetradecylammonio]propane-1-sulfonate [SB3-14] [Figure 1]) enhanced the loadability of natural flavonoid dye (quercetin) in wool and enhanced its antioxidant properties ( Figure 1 ). 14 Nonionic surfactants have non-dissociable chemical structures in their hydrophilic groups, such as amides, alcohols, esters, ethers, or phenols.…”