Use of Ionic Liquids-like Surfactants for the Generation of Unilamellar Vesicles with Potential Applications in Biomedicine

Abstract

The goal of this work is to understand the influence of the counterion nature on the organized systems formed by 1,4-bis-2-ethylhexylsulfosuccinate surfactants in aqueous solutions and, how these aggregates will have influence on the DNAsurfactants interactions. With this in mind, two ionic liquid-like surfactants were investigated: 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate (bmim-AOT) and 1-hexyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate (hmim-AOT). Measurements of dynamic light scattering (DLS), zeta potential, TEM images, fluorescence and UV-Visible spectroscopy were performed in order to study the characteristics of the vesicles formed by bmim-AOT and hmim-AOT. Regarding the determination of the interaction of the surfactants with DNA, circular dichroism was used. The results obtained showed that bmim-AOT and hmim-AOT ionic liquid-like surfactants spontaneously form unilamellar vesicles in water at very low surfactant concentrations. The characteristics of these aggregates are dependent on the length of the tail of the counterions. The length of the hydrophobic chains of the counterions also influences on the DNA:surfactant interactions through hydrophobic effects.

Influence of the AOT Counterion Chemical Structure on the Generation of Organized Systems

“…61 We previously observed by DLS that the surfactants bmim-AOT and hmim-AOT form vesicles in water. 51 In this work, aqueous solutions of emim-AOT in water were prepared in a concentration range from 1 × 10 −4 to 2 × 10 −2 M, and the samples were analyzed by DLS. Table 1 shows the apparent hydrodynamic diameter, d app , values obtained for emim-AOT in water at 298 K. In Figure S3 (Supporting Information), the DLS intensity plot for emim-AOT in water at [surfactant] = 1 × 10 −2 M is depicted.…”

“…Therefore, all factors that increase the v value and/or decrease the a value increase the packaging parameter that affects the size of the micelles. 71 Based on the results obtained in this work and considering those obtained previously from the IL-like surfactants bmim-AOT and hmim-AOT in water, 51 a similar reasoning can be applied. The IL-like surfactant emim-AOT forms direct micelles, like the Na-AOT surfactant, but larger because of the substitution of the Na + counterion by emim + .…”

“…The latter have a p value between 1/2 and 1, so they form vesicles in water. 51 Scheme 2 postulates the ion distribution around the interface in both micelles.…”

“…Besides, thinking about future applications such as the design of catalysts, the flat geometry of the imidazolium ring can also be a significant aspect to consider. 48−50 Recently, 46,51 we reported the synthesis of two IL-like surfactants 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate and 1-hexyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate (bmim-AOT and hmim-AOT, respectively, Scheme 1). In comparison with Na-AOT, these IL-like surfactants showed very different properties.…”

“…In comparison with Na-AOT, these IL-like surfactants showed very different properties. 46,51 Particularly, we studied the physicochemical properties of the aggregates formed by bmim-AOT and hmim-AOT in different solvents. 46,47 Taking into account, the effect of the AOT counterion structure on the self-assembly process is investigated.…”