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Considerable interest in designing multi-responsive soft materials for diverse applications is leading to the development of systems that are embedded with functional groups with stimuli-responsive characters. Surface-active ionic liquids (SAILs) with an ability to form various structural aggregates represent an interesting candidate for designing soft materials with stimuli-responsive characters. Embedding photo-responsive moieties into SAILs with existing pH-responsive properties can unlock a broader range of potential uses. Herein, we prepared photo- and pH-responsive catanionic giant vesicles (GVs) through a synergetic interaction between the pH-responsive choline oleate ([Ch][Ol]) and photo-responsive (4-methyl-4-(2-(octyloxy)-2-oxoethyl)) morpholin-4-ium(E)-4-((4-(dimethylamino) phenyl) diazinyl) benzenesulfonate ([C8EMorph][MO]). The photo-responsiveness in the GVs was introduced through [C8EMorph][MO], which shows E–Z isomerisation under 460 nm light irradiation, whereas the pH-responsive character was obtained through [Ch][Ol]. We used absorbance measurements complimented with a computational study to characterize the photo-responsive behaviour. Irradiating the GVs with light of suitable wavelength and changing the pH of the system altered the behaviour of the aggregates. Small-angle neutron scattering (SANS) analysis showed that, before irradiation, the size of the bilayer thickness of the GVs was 28 Å and after irradiation it was increased to 31 Å, leading to an increment in the overall size of the GVs. This was due to the formation of Z-[C8EMorph][MO] after irradiation, which leads to a slight alteration in the interactions between both SAILs. Moreover, the change in pH of the vesicles caused alterations in the size and shape of the vesicles, as confirmed through the SANS analysis. The stability of the GVs in terms of temperature, dilution, and time was analysed to characterise the GVs for practical applications. The insights gained from this study could be valuable for developing materials for these applications such as probes, cargo carriers, and microreactors in future. [ABSTRACT FROM AUTHOR]

Designing 'smart' nano carriers with high drug loading capacities and stimuli-responsive drug release behavior is crucial as they boost therapeutic efficiency while reducing side effects in patients and thereby ameliorate the limitations of traditional drug carriers. In this study, we created a ZIF-8 coated pH-responsive catanionic vesicular nano-aggregated drug delivery platform with high doxorubicin (DOX) loading capacity. The vesicular nano-aggregates were designed through synergistic interaction between the bile salt, sodium deoxycholate (NaDC), with a biocompatible ester-functionalized ionic liquid-based surfactant (ILBS), 4-methyl-4-(2-(dodecyloxy)carbonylmethyl)morpholin-4-ium bromide (C12EMorphBr). A composited drug nano-carrier was produced by coating zeolitic imidazolate framework (ZIF-8) on the surface of drug-loaded catanionic vesicular nano aggregates (DOX loaded NaDC/C12EMorphBr@ZIF-8). The study demonstrates that the ZIF-8 shell, as opposed to the catanionic vesicular system, prevents DOX leakage from the core–shell nanocomposites in response to acidic stimulation. The size of these nanocomposites was characterized using DLS, while their morphology and crystallography were examined using SEM, EDS, and XRD. These comprehensive characterizations solidify the DOX-loaded nanocomposite's integrity, affirming the successful coating of ZIF-8 on the surface of the vesicles (NaDC/C12EMorphBr). The DOX loaded NaDC/C12EMorphBr@ZIF-8 nanocomposites effectively prevented DOX leakage and early release, resulting in targeted drug delivery to the intended site. Furthermore, The DOX-loaded nanocomposite was effective in killing MCF-07 cells, with an IC50 value of 4.35 ± 0.5 μg ml−1. This effort aims to maximize the combined and independent performance of the vesicular system and coated nanocomposites. [ABSTRACT FROM AUTHOR]

The micellization of choline-based anionic surface-active ionic liquids (SAILs) having lauroyl sarcosinate [Sar]−, dodecylsulfate [DS]−, and deoxycholate [Doc]− as counter-ions was investigated in an aqueous medium. Density functional theory (DFT) was employed to investigate the net interactional energy (Enet), extent of non-covalent interactions, and band gap of the choline-based SAILs. The critical micelle concentration (cmc) along with various parameters related to the surface adsorption, counter-ion binding (β), and polarity of the cores of the micelles were deduced employing surface tension measurements, conductometric titrations and fluorescence spectroscopy, respectively. A dynamic light scattering (DLS) system equipped with zeta-potential measurement set-up and small-angle neutron scattering (SANS) were used to predict the size, zeta-potential, and morphology, respectively, of the formed micelles. Thermodynamic parameters such as standard Gibb's free energy and standard enthalpy change of micellization were calculated using isothermal titration calorimetry (ITC). Upon comparing with sodium salt analogues, it was established that the micellization was predominantly governed by the extent of hydration of [Cho]+, the head groups of the respective anions, and the degree of counter-ion binding (β). Considering the concentration dependence of the enzyme–SAIL interactions, aqueous solutions of the synthesized SAILs at two different concentrations (below and above the cmc) were utilized as the medium for testing the enzymatic activity of cellulase. The activity of cellulase was found to be ∼7- to ∼13-fold higher compared to that observed in buffers in monomeric solutions of the SAILs and followed the order: [Cho][Sar] > [Cho][DS] > [Cho][Doc]. In the micellar solution, a ∼4- to 5-fold increase in enzymatic activity was observed. [ABSTRACT FROM AUTHOR]

The evolution of phase behavior and interactions in anionic silica nanoparticles (Ludox HS40), surfactants [non-ionic decaethylene glycol mono-dodecyl ether (C12E10) and anionic sodium dodecyl sulfate (SDS)], and nanoparticle–surfactant solutions in the presence of salt (NaCl) has been studied using small-angle neutron scattering and dynamic light scattering. In an anionic silica nanoparticle solution (1 wt. %), the phase behavior is controlled by salt concentrations (0–1 M) through screening electrostatic interactions. In the case of 1 wt. % surfactant solutions, the anionic SDS surfactant micelles show significant growth upon adding salt, whereas non-ionic surfactant C12E10 micelles remain spherical until a high salt concentration (1 M). In the mixed system of HS40–C12E10, a transition from a highly stable transparent phase to a two-phase turbid system is observed with a small amount of salt addition CS* (∼0.06 M). The single transparent phase of this system corresponds to sterically stabilized micelles-decorated nanoparticles. For the turbid phase, the results are understood in terms of depletion attraction induced by non-adsorption of C12E10 micelles, which explains the appearance of turbidity at a much lower concentration of salt. In the mixed system of similarly charged nanoparticles and micelles (HS40-SDS), the phase behavior is governed by no physical interaction between the components, and salt screens the repulsive interaction among nanoparticles. These results are further utilized to tune multicomponent interactions and phase behavior of nanoparticles with a mixed C12E10-SDS surfactant system in the presence of salt. The mixed surfactants provide tuning of nanoparticle–micelle as well as micelle–micelle interactions to dictate the phase behavior of a nanoparticle–surfactant solution. In these systems, the effective potential can be described by double-Yukawa potential taking account of attractive and repulsive parts at low and intermediate salt concentrations (CS*), the aggregation of nanoparticles is characterized by fractal aggregates. [ABSTRACT FROM AUTHOR]

Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) experiments have been carried out to study the competitive effects of NaCl and sodium dodecyl sulfate (SDS) surfactant on the evolution of the structure and interactions in a silica nanoparticle–Bovine serum albumin (BSA) protein system. The unique advantage of contrast-matching SANS has been utilized to particularly probe the structure of nanoparticles in the multi-component system. Silica nanoparticles and BSA protein both being anionic remain largely individual in the solution without significant adsorption. The non-adsorbing nature of protein is known to cause depletion attraction between nanoparticles at higher protein concentrations. The nanoparticles undergo immediate aggregation in the nanoparticle–BSA system on the addition of a small amount of salt [referred as the critical salt concentration (CSC)], much less than that required to induce aggregation in a pure nanoparticle dispersion. The salt ions screen the electrostatic repulsion between the nanoparticles, whereby the BSA-induced depletion attraction dominates the system and contributes to the nanoparticle aggregation of a mass fractal kind of morphology. Further, the addition of SDS in this system interestingly suppresses nanoparticle aggregation for salt concentrations lower than the CSC. The presence of SDS gives rise to additional electrostatic repulsion in the system by binding with the BSA protein via electrostatic and hydrophobic interactions. For salt concentrations higher than the CSC, the formation of clusters of nanoparticles is inevitable even in the presence of protein–surfactant complexes, but the mass fractal kind of branched aggregates transform to surface fractals. This has been attributed to the BSA–SDS complex induced depletion attraction along with salt-driven screening of electrostatic repulsion. Thus, the interplay of depletion and electrostatic and hydrophobic interactions has been utilized to tune the structures formed in a multicomponent silica nanoparticle–BSA–SDS/NaCl system. [ABSTRACT FROM AUTHOR]