Synergistic Solvation as the Enhancement of Local Mixing

Mixing two solvents can sometimes make a much better solvent than expected from their weighted mean. This phenomenon, called synergistic solvation, has commonly been explained via the Hildebrand and Hansen solubility parameters, yet their inability in other solubilization phenomena, most notably hydrotropy, necessitates an alternative route to elucidating solubilization. While, recently, the universal theory of solubilization was founded on the statistical thermodynamic fluctuation theory (as a generalization of the Kirkwood-Buff theory), its demand for experimental data processing has been a hindrance for its wider application. This can be overcome by the solubility isotherm theory, which is founded on the fluctuation theory yet reduces experimental data processing significantly to the level of isotherm analysis in sorption. The isotherm analysis identifies the driving force of synergistic solvation as the enhancement of solvent mixing around the solute, opposite in behavior to hydrotropy (characterized by the enhancement of demixing or self-association around the solute). Thus, the fluctuation theory, including its solubility isotherms, provides a universal language for solubilization across the historic subcategorization of solubilizers, for which different (and often contradictory) mechanistic models have been proposed.

Role of Deep Eutectic Solvent Precursors as Hydrotropes: Unveiling Synergism/Antagonism for Enhanced Kraft Lignin Dissolution

Lignin holds significant potential as a feedstock for generating valuable aromatic compounds, fuels, and functional materials. However, achieving this potential requires the development of effective dissolution methods. Previous works have demonstrated the remarkable capability of hydrotropes to enhance the aqueous solubility of lignin, an amphiphilic macromolecule. Notably, deep eutectic solvents (DESs) have exhibited hydrotropic behavior, significantly increasing the aqueous solubility of hydrophobic solutes, making them attractive options for lignin dissolution. This study aimed at exploring the influence of hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) on the performance of DESs as hydrotropes for lignin dissolution, while possible dissolution mechanisms in different water/DES compositions were discussed. The capacity of six alcohols (glycerol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol) and cholinium chloride to enhance the solubility of Kraft lignin in aqueous media was investigated. A correlation between solubility enhancement and the alkyl chain length of the alcohol was observed. This was rationalized upon the competition between hydrotrope-hydrotrope and solute-hydrotrope aggregates with the latter being maximized for 1,4-butanediol. Interestingly, the hydrotropic effect of DESs on lignin solubility is well represented by the independent sum of the dissolving contributions from the corresponding HBAs and HBDs in the diluted region. Conversely, in the concentrated region, the solubility of lignin for a certain hydrotrope concentration was always found to be higher for the pure hydrotropes rather than their combined HBA/HBD counterparts.

Kirkwood-Buff Analysis of Binary and Ternary Systems Consisting of Alcohols (Methanol, Ethanol, 1-Propanol, and 2-Propanol), Water, and n-Hexane to Understand the Formation of Surfactant-Free Microemulsions

Surfactant-free microemulsion (SFME) represents a class of fluid mixtures that can form microheterogeneous structures without detergents, offering an environmentally benign alternative to traditional microemulsions. However, the formation mechanism is still elusive. This work applies the Kirkwood-Buff theory to mixtures of alcohols, water, and n-hexane to elucidate the SFME formation mechanism. To ensure robust calculation of the Kirkwood-Buff integrals (KBIs), we construct a data set of densities and excess free energies of binary and ternary systems. Multiple excess Gibbs free energy models are assessed against this data set to select the most suitable model reproducing the experimental results. In addition, we introduce statistical methods to determine the optimal polynomial order of the Redlich-Kister correlation for the excess volume data. We first validate our methodology in binary systems. Then, we extend the calculation method to ternary mixtures. The KBI calculation results reveal that the alcohol-hexane and water-hexane interactions do not significantly affect SFME formation. In contrast, the interplay among water-water, water-alcohol, and alcohol-alcohol interactions critically influences the ability of a liquid mixture to form SFME structures. SFME systems exhibit the facile formation of water aggregates enveloped by alcohols, whereas non-SFME systems demonstrate homogeneous alcohol/water droplets dispersed in an oil continuous medium.

Exploring the impact of sodium salts on hydrotropic solubilization

Some ionic liquids (ILs) were shown to display a strong ability to enhance the solubility of phenolic compounds through hydrotropy. However, evidence shows that salt ions in hydrotropic aqueous solutions may change the behavior of molecules by promoting possible interactions between the components of the system, thus causing changes in solubility. Herein, we study the impact of sodium salt anions on the hydrotropic dissolution of syringic acid using 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) as a hydrotrope, with a focus on dicyanamide Na[N(CN)2] and thiocyanate Na[SCN] salts. Dynamic light scattering, Raman spectroscopy, and nuclear magnetic resonance spectroscopy were used to investigate how the mixture of IL-salts affects the solvation. The results obtained show that [C4mim]Cl is able to increase the solubility of syringic acid 80-fold. Despite their structural similarities, the presence of Na[N(CN)2] or Na[SCN] in an aqueous solution of [C4mim]Cl induced opposite solubility trends. The addition of Na[N(CN)2] promotes a higher ability to solubilize syringic acid than in the corresponding IL system due to a pH buffering effect, resulting in the deprotonation of the solute. The addition of Na[SCN], on the other hand, induces a relative decrease in syringic acid solubilization at higher concentrations of ILs due to the negative contribution of the NaCl formed by anion-exchange. These results emphasise the often overlooked pH contribution provided by ILs for biomolecule solubilisation whilst providing experimental insights into the structure of aqueous solutions of ionic liquids and the role it plays in the formation of IL-salt aggregates.

Progress in the field of hydrotropy: mechanism, applications and green concepts

Sustainability and greenness are the concepts of growing interest in the area of research as well as industries. One of the frequently encountered challenges faced in research and industrial fields is the solubility of the hydrophobic compound. Conventionally organic solvents are used in various applications; however, their contribution to environmental pollution, the huge energy requirement for separation and higher consumption lead to unsustainable practice. We require solvents that curtail the usage of hazardous material, increase the competency of mass and energy and embrace the concept of recyclability or renewability. Hydrotropy is one of the approaches for fulfilling these requirements. The phenomenon of solubilizing hydrophobic compound using hydrotrope is termed hydrotropy. Researchers of various fields are attracted to hydrotropy due to its unique physicochemical properties. In this review article, fundamentals about hydrotropes and various mechanisms involved in hydrotropy have been discussed. Hydrotropes are widely used in separation, heterogeneous chemical reactions, natural product extraction and pharmaceuticals. Applications of hydrotropes in these fields are discussed at length. We have examined the significant outcomes and correlated them with green engineering and green chemistry principles, which could give an overall picture of hydrotropy as a green and sustainable approach for the above applications.

Boosting antibiotics performance by new formulations with deep eutectic solvents

The critical scenario of antimicrobial resistance to antibiotics highlights the need for improved therapeutics and/or formulations. Herein, we demonstrate that deep eutectic solvents (DES) formulations are very promising to remarkably improve the solubility, stability and therapeutic efficacy of antibiotics, such as ciprofloxacin. DES aqueous solutions enhance the solubility of ciprofloxacin up to 430-fold while extending the antibiotic stability. The developed formulations can improve, by 2 to 4-fold, the susceptibility of Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria to the antibiotic. They also improve the therapeutic efficacy at concentrations where bacteria present resistance, without promoting tolerance development to ciprofloxacin. Furthermore, the incorporation of DES decreases the toxicity of ciprofloxacin towards immortalized human epidermal keratinocytes (HaCat cells). The results herein reveal the pioneering use of DES in fluoroquinolone-based formulations and their impact on the antibiotic's characteristics and on its therapeutic action.

The Impact of Size and Shape in the Performance of Hydrotropes: A Case-Study of Alkanediols

Inspired by the recently proposed cooperative mechanism of hydrotropy, where water molecules mediate the aggregation of hydrotrope around the solute, this work studies the impact of apolar volume and polar...

Assessing the hydrotropic effect in the presence of electrolytes: competition between solute salting-out and salt-induced hydrotrope aggregation

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....

Temperature Dependence of Sorption

Understanding how sorption depends on temperature on a molecular basis has been made difficult by the coexistence of isotherm models, each assuming a different sorption mechanism and the routine application of planar, multilayer sorption models (such as Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAB)) beyond their premises. Furthermore, a common observation that adsorption isotherms measured at different temperatures fall onto a single "characteristic curve" when plotted against the adsorption potential has not been given a clear explanation, due to its ambiguous foundation. Extending our recent statistical thermodynamic fluctuation theory of sorption, we have generalized the classical isosteric theory of sorption into a statistical thermodynamic fluctuation theory and clarified how sorption depends on temperature. We have shown that a characteristic curve exists when sorbate number increment contributes purely energetically to the interface, whereas the correlation between sorbate number and entropy drives the temperature dependence of an isotherm. This theory rationalizes the opposite temperature dependence of water vapor sorption on activated carbons with uniform versus broad pore size distributions and can be applied to moisture sorption on starch gels. The adsorption potential is a convenient variable for sorption in its ability to unify sorbate-sorbate fluctuation and the isosteric thermodynamics of sorption.

Cooperative Sorption on Porous Materials

The functional shape of a sorption isotherm is determined by underlying molecular interactions. However, doubts have been raised on whether the sorption mechanism can be understood in principle from analyzing sorption curves via a range of competing models. We have shown recently that it is possible to translate a sorption isotherm to the underlying molecular interactions via rigorous statistical thermodynamics. The aim of this paper is to fill the gap between the statistical thermodynamic theory and analyzing experimental sorption isotherms, especially of microporous and mesoporous materials. Based on a statistical thermodynamic approach to interfaces, we have derived a cooperative isotherm, as a generalization of the Hill isotherm and our cooperative solubilization model, without the need for assumptions on adsorption sites, layers, and pore geometry. Instead, the statistical characterization of sorbates, such as the sorbate-interface distribution function and the sorbate number distribution, as well as the existence of statistically independent units of the interface, underlies the cooperative sorption isotherm. Our isotherm can be applied directly to literature data to reveal a few key system attributes that control the isotherm: the cooperative number of sorbates and the free energy of transferring sorbates from the saturated vapor to the interface. The sorbate-sorbate interaction is quantified also via the Kirkwood-Buff integral and the excess numbers.

Acid Hydrotropic Fractionation of Lignocelluloses for Sustainable Biorefinery: Advantages, Opportunities, and Research Needs

This Minireview provides a comprehensive discussion on the potential of using acid hydrotropes for sustainably fractionating lignocelluloses for biorefinery applications. Acid hydrotropes are a class of acids that have hydrotrope properties toward lignin, which helps to solubilize lignin in aqueous systems. With the capability of cleaving ether and ester bonds and even lignin-carbohydrate complex (LCC) linkages, these acid hydrotropes can therefore isolate lignin embedded in the plant biomass cell wall and subsequently solubilize the isolated lignin in aqueous systems. Performances of two acid hydrotropes, that is, an aromatic sulfonic acid [p-toluenesulfonic acid (p-TsOH)] and a dicarboxylic acid [maleic acid (MA)], in terms of delignification and dissolution of hemicelluloses, and reducing lignin condensation, were evaluated and compared. The advantages of lignin esterification by MA for producing cellulosic sugars through enzymatic hydrolysis and lignin-containing cellulose nanofibrils (LCNFs) through mechanical fibrillation from the fractionated water insoluble solids (WIS), and for obtaining less condensed lignin with light color, were demonstrated. The excellent enzymatic digestibility of maleic acid hydrotropic fractionation WISs was also demonstrated by comparing with WISs from other fractionation processes. The recyclability and reusability of acid hydrotropes were also reviewed. Finally, perspectives on future research needs to address key technical issues for commercialization were also provided.

Sorption: A Statistical Thermodynamic Fluctuation Theory

Can the sorption mechanism be proven by fitting an isotherm model to an experiment? Such a question arises because (i) multiple isotherm models, with different assumptions on sorption mechanisms, often fit an experimental isotherm equally well, (ii) some isotherm models [such as Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAB)] fit experimental isotherms that do not satisfy the underlying assumptions of the model, and (iii) some isotherms (such as Oswin and Peleg) are empirical equations that do not have a well-defined basis on sorption mechanisms. To overcome these difficulties, we propose a universal route of elucidating the sorption mechanism directly from an experimental isotherm, without an isotherm model, based on the statistical thermodynamic fluctuation theory. We have shown that how sorbate-sorbate interaction depends on activity is the key to understanding the sorption mechanism. Without assuming adsorption sites and planar layers, an isotherm can be derived, which contains the Langmuir, BET, and GAB models as its special cases. We have constructed a universal approach applicable to adsorption and absorption, solid and liquid sorbents, and vapor and liquid sorbates and demonstrated its efficacy using the humidity sorption isotherm of sucrose from both the solid and liquid sides.

Role of Hydrotropes in Sparingly Soluble Drug Solubilization: Insight from a Molecular Dynamics Simulation and Experimental Perspectives

Drug molecules' therapeutic efficacy depends on their bioavailability and solubility. But more than 70% of the formulated drug molecules show limited effectiveness due to low water solubility. Thus, the water solubility enhancement technique of drug molecules becomes the need of time. One such way is hydrotropy. The solubilizing agent of a hydrophobic molecule is generally referred to as a hydrotrope, and this phenomenon is termed hydrotropy. This method has high industrial demand, as hydrotropes are noninflammable, readily available, environmentally friendly, quickly recovered, cost-effective, and not involved in solid emulsification. The endless importance of hydrotropes in industry (especially in the pharmaceutical industry) motivated us to prepare a feature article with a clear introduction, detailed mechanistic insights into the hydrotropic solubilization of drug molecules, applications in pharma industries, and some future directions of this technique. Thus, we believe that this feature article will become an adequate manual for the pharmaceutical researchers who want to explore all of the past perspectives of the hydrotropic action of hydrotropes in pharmaceutics.

Cholinium-based ionic liquids as bioinspired hydrotropes to tackle solubility challenges in drug formulation

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.

Cooperativity in micellar solubilization

Sudden onset of solubilization is observed widely around or below the critical micelle concentration (CMC) of surfactants. It has also been reported that micellization is induced by the solutes even below CMC and the solubilized solute increases the aggregation number of the surfactant. These observations suggest enhanced cooperativity in micellization upon solubilization. Recently, we have developed a rigorous statistical thermodynamic theory of cooperative solubilization. Its application to hydrotropy revealed the mechanism of cooperative hydrotropy: hydrotrope self-association enhanced by solutes. Here we generalize our previous cooperative solubilization theory to surfactants. We have shown that the well-known experimental observations, such as the reduction of CMC in the presence of the solutes and the increase of aggregation number, are the manifestations of cooperative solubilization. Thus, the surfactant self-association enhanced by a solute is the driving force of cooperativity and a part of a universal cooperative solubilization mechanism common to hydrotropes and surfactants at low concentrations.

The impact of the counterion in the performance of ionic hydrotropes

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.

Fluctuation adsorption theory: quantifying adsorbate-adsorbate interaction and interfacial phase transition from an isotherm

How adsorbate-adsorbate interaction determines the functional shape of an adsorption isotherm is an important and challenging question. Many models for the adsorption isotherm have been proposed to answer this question. However, a successful fitting of an isotherm on its own is insufficient to prove the correctness of the model assumptions. Instead, starting from the principles of statistical thermodynamics, we propose how adsorbate-adsorbate interactions can be quantified from an isotherm. This was made possible by extending the key tools of solution statistical thermodynamics to adsorbates at the interface, namely, the Kirkwood-Buff and McMillan-Mayer theories, as well as their relationship to the thermodynamic phase stability condition. When capillary condensation and interfacial phase transition are absent, adsorbate-adsorbate interactions can be quantified from an isotherm using the Kirkwood-Buff integrals, and virial coefficients can yield multiple-body interaction between adsorbates. Such quantities can be obtained directly from the fitting parameters for the well-known isotherm models (e.g., Langmuir, BET). The size of the adsorbate cluster involved in capillary condensation and interfacial phase transition can also be evaluated from the isotherm, which was demonstrated for the adsorption isotherm of water on activated carbons of varying pore sizes from the literature. Signatures of isotherm classifications by IUPAC have been characterized in terms of multiple-body interactions between adsorbates.

Using coarse-grained molecular dynamics to rationalize biomolecule solubilization mechanisms in ionic liquid-based colloidal systems

Solubilizing agents are widely used to extract poorly soluble compounds from biological matrices. Aqueous solutions of surfactants and hydrotropes are commonly used as solubilizers, however, the underlying mechanism that determines their action is still roughly understood. Among these, ionic liquids (IL) are often used not only for solubilization of a target compound but in liquid-liquid extraction processes. Molecular dynamics simulations can shed light into this issue by providing a microscopic insight of the interactions between solute and solubilising agents. In this work, a new coarse-grained (CG) model was developed under the MARTINI framework for gallic acid (GA) while the CG models of three quaternary ammonium ionic liquids and salts (QAILS) were obtained from literature. Three QAILS were selected bearing in mind their potential solubilising mechanisms: trimethyl-tetradecylammonium chloride ([N1,1,1,14]Cl) as a surfactant, tetrabutylammonium chloride ([N4,4,4,4]Cl) as a hydrotrope, and tributyl-tetradecylammonium chloride ([N4,4,4,14]Cl) as a system combining the characteristics of the other compounds. Throughout this hydrotrope-to-surfactant spectrum and considering the most prevalent GA species across the pH range, the solvation of GA at two concentration levels in aqueous QAILS solutions were studied and discussed. The results of this study indicate that dispersive interactions between the QAILS and GA are generally the driving force in the GA solubilization. However, electrostatic interactions play an increasingly significant role as the GA becomes deprotonated, affecting their placement within the micelle and ultimately the solvation mechanism. The hydrotropic mechanism seen in [N4,4,4,4]Cl corroborates recent models based on the formation of a hydrotrope-solute aggregates driven by dispersive forces. This work contributes to the application of a transferable approach to partition and solubilization studies using molecular dynamics, which could complement experimental assays and quickly screen molecular candidates for these processes.

Aggregation Behavior and Thermodynamic Studies of Hydrotropes: A Review

Under the aspect of strict environmental regulations, hydrotropy is accepted as an environmentally friendly (“green”) approach to solubilise hydrophobic compounds. Above the minimum hydrotrope concentration (MHC), hydrotropes are capable of self-aggregation; the MHC is considered the minimum requirement for solubilisation. In this article a comprehensive overview of the aggregation behaviour of different hydrotropes is presented. Details about the methods used for aggregation are given. The role of additives is discussed with respect to their influence on the MHC. Thermodynamic studies are used to evaluate the stability of a hydrotrope at different temperatures. A modern approach to the solubilization mechanism using hydrotropes is also presented in this review article. The aim of this article is to provide guidance for conducting such studies on a number of hydrotropes.

Unveiling the mechanism of hydrotropy: evidence for water-mediated aggregation of hydrotropes around the solute

The mechanism of hydrotropy is experimentally proven in this work. Apolarity is shown to be the driving force of hydrotropy.

Drug Solubilization by Means of Partition/Association Equilibrium Using a Modified Nanosized Dendrimeric Biopolymer

The objective of this study is to elucidate the combined effects of a novel type of material being investigated as a new excipient, an octenylsuccinate-modified dendrimer-like biopolymer (OS-DLB) and poloxamer (PLX), on the solubility of poorly water-soluble compounds. Phenytoin (PHT), griseofulvin (GSF), ibuprofen (IBU), and loratadine (LOR) were used as model compounds. Phase solubility measurements were conducted to determine the relative proportions of API, OS-DLB, and PLX that result in the most stable dendrimeric complexes. The solubilizing power of OS-DLB increases with increasing hydrophobicity of the solute. In the presence of PLX, the solubilization effect of OS-DLB is modestly accentuated for the most hydrophobic drugs (IBU and LOR) but has no effect on the least hydrophobic one (PHT). The maximum potentiation effect of PLX on the solubilizing properties of OS-DLB was observed for GSF, the drug of intermediate hydrophobicity. Three different types of solubilization profiles were obtained in the study. All three different profiles can be appropriately described by a single solubilization model, depending on the specific parameter values. The defining parameters of the model reflect the hydrophobicity of the drug on the one hand and, on the other hand, the inherent tendency of the drug (crystal lattice energy) toward crystallization.

Geminal Diol of Dihydrolevoglucosenone as a Switchable Hydrotrope: A Continuum of Green Nanostructured Solvents

The addition of water to dihydrolevoglucosenone (Cyrene) creates a solvent mixture with highly unusual properties and the ability to specifically and efficiently solubilize a wide range of organic compounds, notably, aspirin, ibuprofen, salicylic acid, ferulic acid, caffeine, and mandelic acid. The observed solubility enhancement (up to 100-fold) can be explained only by the existence of microenvironments mainly centered on Cyrene's geminal diol. Surprisingly, the latter acts as a reversible hydrotrope and regulates the polarity of the created complex mixture. The possibility to tune the polarity of the solvent mixture through the addition of water, and the subsequent generation of variable amounts of Cyrene's geminal diol, creates a continuum of green solvents with controllable solubilization properties. The effective presence of microheterogenieties in the Cyrene/water mixture was adequately proven by (1) Fourier transform infrared/density functional theory showing Cyrene dimerization, (2) electrospray mass-spectrometry demonstrating the existence of dimers of Cyrene's geminal diol, and (3) the variable presence of single or multiple tetramethylsilane peaks in the ¹H NMR spectra of a range of Cyrene/water mixtures. The Cyrene-water solvent mixture is importantly not mutagenic, barely ecotoxic, bioderived, and endowed with tunable hydrophilic/hydrophobic properties.

Ab initio prediction of structuring/mesoscale inhomogeneities in surfactant-free microemulsions and hydrogen-bonding-free microemulsions

Prediction of microemulsion-like structuring in surfactant-free and hydrogen-bonding-free systems.

Facile Strategy Enabling Both High Loading and High Release Amounts of the Water-Insoluble Drug Clofazimine Using Mesoporous Silica Nanoparticles

The use of nanocarriers to deliver poorly soluble drugs to the sites of diseases is an attractive and general method, and mesoporous silica nanoparticles (MSNs) are increasingly being used as carriers. However, both loading a large amount of drugs into the pores and still being able to release the drug is a challenge. In this paper, we demonstrate a general strategy based on a companion molecule that chaperones the drug into the pores and also aids it in escaping. A common related strategy is to use a miscible co-solvent dimethyl sulfoxide (DMSO), but although loading may be efficient in DMSO, this co-solvent frequently diffuses into an aqueous environment, leaving the drug behind. We demonstrate the method by using acetophenone (AP), an FDA-approved food additive as the chaperone for clofazimine (CFZ), a water-insoluble antibiotic used to treat leprosy and multidrug-resistant tuberculosis. AP enables a high amount of CFZ cargo into the MSNs and also carries CFZ cargo out from the MSNs effectively when they are in an aqueous biorelevant environment. The amount of loading and the CFZ release efficiency from MSNs were optimized; 4.5 times more CFZ was loaded in MSNs with AP than that with DMSO and 2300 times more CFZ was released than that without the assistance of the AP. In vitro treatment of macrophages infected by Mycobacterium tuberculosis with the optimized CFZ-loaded MSNs killed the bacteria in the cells in a dose-dependent manner. These studies demonstrate a highly efficient method for loading nanoparticles with water-insoluble drug molecules and the efficacy of the nanoparticles in delivering drugs into eukaryotic cells in aqueous media.

Enhanced dissolution of ibuprofen using ionic liquids as catanionic hydrotropes

Ionic liquids as powerful hydrotropes for ibuprofen, where both cation and anion may contribute to the hydrotropic mechanism in a synergistic manner.

Statistical thermodynamic foundation for mesoscale aggregation in ternary mixtures

The origin of persistent mesoscale aggregation around the plait point has been clarified from statistical thermodynamics and differential geometry.

Concentrated Aqueous Sodium Tosylate as Green Medium for Alkene Oxidation and Nucleophilic Substitution Reactions

A hydrotropic solution of highly concentrated sodium tosylate (NaOTs) can be used as a recyclable medium for the environmentally benign oxidation of conjugated alkenes with H₂O₂. Both uncatalyzed and metal-catalyzed reactions provided the corresponding oxidation products in higher yields than in pure water or many common organic solvents.

Unifying hydrotropy under Gibbs phase rule

A rational approach, aiming at constructing a unified theory of hydrotropy, will be presented based upon the first principles of statistical thermodynamics.

Statistical thermodynamics unveils the dissolution mechanism of cellobiose

Statistical thermodynamic analysis of cellobiose solubility in aqueous salts sheds light on the mechanism of cellulose solubilization on a molecular scale.

PPh4Cl in aqueous solution – the aggregation behavior of an antagonistic salt

The aggregation behavior of the antagonistic salt PPh₄Cl was investigated. This salt was found to be an excellent hydrotrope which does not aggregate in binary aqueous solutions or in a ternary one, upon the addition of the exemplary hydrophobic molecule DR-13.

The impact of the structuring of hydrotropes in water on the mesoscale solubilisation of a third hydrophobic component

The complex structuring of alcohols in water influences the mesoscale solubilisation of a third component depending on its nature.

Hydrotropy and scattering: pre-ouzo as an extended near-spinodal region

The relationship between hydrotropic solubilization and mesoscale structuring has been clarified from the first principles of chemical and statistical thermodynamics.