A recent proposal attributes the origin of hydrotropy to the water-mediated aggregation of hydrotrope molecules around the solute. Experimental evidence for this phenomenon is reported for the first ...time in this work, using
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H-NMR. A new computational technique to quantify apolarity is introduced and is used to show that apolarity of both solute and hydrotrope is the driving force of hydrotropy.
The mechanism of hydrotropy is experimentally proven in this work. Apolarity is shown to be the driving force of hydrotropy.
Aqueous micellar two-phase systems (AMTPS) hold a large potential for cloud point extraction of biomolecules but are yet poorly studied and characterized, with few phase diagrams reported for these ...systems, hence limiting their use in extraction processes. This work reports a systematic investigation of the effect of different surface-active ionic liquids (SAILs)covering a wide range of molecular propertiesupon the clouding behavior of three nonionic Tergitol surfactants. Two different effects of the SAILs on the cloud points and mixed micelle size have been observed: ILs with a more hydrophilic character and lower critical packing parameter (CPP < 1/2) lead to the formation of smaller micelles and concomitantly increase the cloud points; in contrast, ILs with a more hydrophobic character and higher CPP (CPP ≥ 1) induce significant micellar growth and a decrease in the cloud points. The latter effect is particularly interesting and unusual for it was accepted that cloud point reduction is only induced by inorganic salts. The effects of nonionic surfactant concentration, SAIL concentration, pH, and micelle ζ potential are also studied and rationalized.
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The utilization of natural compounds, such as phenolic acids and biopolymers, in the healthcare domain is gaining increasing attention. In this study, bacterial nanocellulose (BC) ...membranes were loaded with ionic liquids (ILs) based on phenolic acids. These ionic compounds, with improved solubility and bioavailability, were prepared by combining the cholinium cation with anions derived from caffeic, ellagic and gallic acids. The obtained BC-ILs membranes were homogeneous, conformable and their swelling ability agreed with the solubility of each IL. These membranes revealed a controlled ILs dissolution rate in the wet state and high antioxidant activity. In vitro assays performed with Raw 264.7 macrophages and HaCaT keratinocytes revealed that these novel BC-ILs membranes are non-cytotoxic and present relevant anti-inflammatory properties. Diffusion studies with Hanson vertical diffusion cells showed a prolonged release profile of the ILs from the BC membranes. Thus, this work, successfully demonstrates the potential of BC-ILs membranes for skin treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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Hydrotropy is a well-established strategy to enhance the aqueous solubility of hydrophobic drugs, facilitating their formulation for oral and dermal delivery. However, most ...hydrotropes studied so far possess toxicity issues and are inefficient, with large amounts being needed to achieve significant solubility increases. Inspired by recent developments in the understanding of the mechanism of hydrotropy that reveal ionic liquids as powerful hydrotropes, in the present work the use of cholinium vanillate, cholinium gallate, and cholinium salicylate to enhance the aqueous solubility of two model drugs, ibuprofen and naproxen, is investigated.
It is shown that cholinium vanillate and cholinium gallate are able to increase the solubility of ibuprofen up to 500-fold, while all three ionic liquids revealed solubility enhancements up to 600-fold in the case of naproxen. Remarkably, cholinium salicylate increases the solubility of ibuprofen up to 6000-fold. The results obtained reveal the exceptional hydrotropic ability of cholinium-based ionic liquids to increase the solubility of hydrophobic drugs, even at diluted concentrations (below 1 mol·kg−1), when compared with conventional hydrotropes. These results are especially relevant in the field of drug formulation due to the bio-based nature of these ionic liquids and their low toxicity profiles. Finally, the solubility mechanism in these novel hydrotropes is shown to depend on synergism between both amphiphilic ions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Superactivity is the increase on the enzymatic activity promoted by microemulsion formation.•Microemulsions inducing superactivity are formed by surfactants or surface active ILs.•Superactivation of ...various enzymes, in diverse reactions and by various surfactants is analyzed.•The ILs tunability is the vehicle toward new methodologies promoting the enzyme activation.•A multidisciplinary study is needed to understand the phenomenon and its industrial application.
The superactivity phenomenon is a concept that expresses a significant increase on the enzymatic activity by common surfactants or ionic liquids emulsions. In this context, this work presents an overview of the literature on this subject, focused on the type, and characteristics of the surfactants and ILs reported in literature as superactivity inductors and the enzymes and reactions hitherto investigated in the superactivity context. It intends to emphasize the necessity of a multidisciplinary approach to this subject bringing together scientific communities of different fields to foster the understanding of this phenomenon, and to identify the type of reactions and processes that could and should be improved by it, having into account its potential application at industrial level.
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Aqueous biphasic systems constituted by ionic liquids (IL-based ABSs) are a target of investigation in the separation of high-value biomolecules. However, identification of the molecular-level ...mechanisms ruling the two-phase formation and extraction performance of these systems is crucial to the successful design of effective separation processes. In this work, IL-based ABSs formed by K2HPO4 and cholinium carboxylate ILs (ChC n CO2 with n = 1–7, comprising anions with odd and even alkyl chain lengths) were investigated. The corresponding ternary phase diagrams, including binodal curves, tie-lines, tie-line lengths, and critical points, as well as the Setschenow salting-out coefficients (k s), which quantitatively describe the two-phase formation ability, were determined at 298 K. The extraction capability of these systems was then evaluated for four amino acids (l-tryptophan, l-phenylalanine, l-tyrosine, and l-3,4-dihydroxyphenylalanine/l-dopa). It was found that ILs composed of anions with even alkyl chains display slightly higher k s values, meaning that these ILs are more easily salted out or more easily phase-separated to form ABSs, whereas ABSs formed by ILs with anions comprising odd alkyl chains lead to slightly higher partition coefficients of amino acids. Beyond the neat IL odd–even effect resulting from their nanostructuration, being this a well-known phenomenon occurring in a series of their thermophysical properties, the existence of an odd–even effect displayed by the IL anion aliphatic moiety in aqueous solution is shown here, visible in both the two-phase formation ability and extraction performance of ABSs. These findings contribute to elucidate of the molecular-level mechanisms governing ABS formation and partitioning of biomolecules, ultimately contributing to the design of proficient separation platforms.
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Although magnetic ionic liquids (MILs) are not yet industrially applied, their continued development and eventual commercial use may lead to their appearance into the aquatic ecosystem through ...accidental spills or effluents, consequently promoting aquatic contaminations. Furthermore, the deficient information and uncertainty surrounding the environmental impact of MILs could be a major barrier to their widespread industrial application and international registration. Thus, in the present work, a range of cholinium salt derivatives with magnetic properties was synthesized and their ecotoxicity was evaluated towards the luminescent bacteria Vibrio fischeri. The results suggest that all MILs structures tested are moderately toxic, or even toxic, to the bacteria. Furthermore, their toxicity is highly dependent on the structural modifications of the cation, namely the alkyl side chain length and the number of hydroxyethyl groups, as well as the atomic number of the metal anion. Finally, from the magnetic anions evaluated, the MnCl42- is the less toxic. In order to improve the knowledge for the prospective design of environmentally safer MILs, it is important to expand this study to other aquatic organisms at different trophic levels.
•Cholinium salt derivatives with magnetic properties (MILs) was synthesized.•Their ecotoxicity was evaluated towards the luminescent bacteria Vibrio fischeri.•All MILs structures tested are moderately toxic, or even toxic, to the bacteria.•Their toxicity is highly dependent on the structural modifications.
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Cell membrane models have been used to evaluate the interactions of various imidazolium-based ionic liquids (ILs) with Langmuir monolayers of two types of phospholipids and cholesterol. Data from ...surface pressure isotherms, Brewster angle microscopy (BAM) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) pointed to significant effects on the monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol, used to mimic the membranes of eukaryotic cells, for ILs containing more than 6 carbon atoms in the alkyl chain (i.e. n > 6). For ILs with less hydrophobic tails (n ≤ 6) and low concentrations, the effects were almost negligible, therefore, such ILs should not be toxic to eukaryotic cells. The hydrophobicity of the anion was also proved to be relevant, with larger impact from ILs containing tetrafluoroborate (BF4-) than chloride (Cl-). Molecular dynamics simulations for DPPC monolayers at the surface of aqueous solutions of alkylimidazolium chloride (CnmimCl) confirm the penetration of the IL cations with longer alkyl chains into the phospholid monolayer and provide information on their location and orientation within the monolayer. For monolayers of dipalmitoylphosphatidyl glycerol (DPPG), which is negatively charged like bacteria cell membranes, the ILs induced much larger effects. Similarly to the results for DPPC and cholesterol, effects increased with the number of carbon atoms in the alkyl chain and with a more hydrophobic anion BF4-. Overall, the approach used can provide relevant information of molecular-level interactions behind the toxicity mechanisms and support the design of (quantitative) structure-activity relationship models, which may help design more efficient and environmentally friendly ILs.
The efficiency of an ionic hydrotrope is shown to increase with the hydrophobicity of its counterion, challenging the common view that ionic hydrotropes should possess a small, densely charged ...counterion such as sodium or chloride.
Highly hydrophilic counterions such as sodium or chloride are not good choices as counterions to achieve efficient hydrotropy.
Water solubility enhancement is a long-standing challenge in a multitude of chemistry-related fields. Hydrotropy is a simple and efficient method to improve the solubility of hydrophobic molecules in ...aqueous media. However, the mechanism behind this phenomenon remains controversial. Herein the impact of salt doping on the hydrotropy phenomenon is determined experimentally using the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (C
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mimCl) as a hydrotope and vanillin as a solute. Hydrophobic interactions were found to be central to the aggregation of the hydrotrope around the solute, and seem to drive hydrotropy. Furthermore,
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H-NMR analysis indicates that hydrotrope-solute interactions present a degree of site-specificity. The addition of chloride salts in the presence of higher IL concentrations promotes a greater relative decrease of the vanillin solubility than in the corresponding system without the IL. This was assigned to the negative impact of increased hydrotrope pre-aggregation in the presence of inorganic salts. The results were rationalised using statistical thermodynamics through which hydrotrope aggregation prior to solute addition is shown to be detrimental to the hydrotropic effect, seemingly confirming solute-induced clustering of the hydrotrope to be the predominant mechanism of hydrotropy.
Hydrotrope pre-aggregation in the presence of inorganic salts is detrimental to the hydrotropic effect. Hydrotropic solubilization is determined by hydrotrope and solute aggregation and driven mainly by hydrophobic interactions.
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