Impact of amphiphilic biomass-dissolving ionic liquids on biological cells and liposomes

Effects of α-olefin sulfonate (AOS) on Tubifex tubifex: toxicodynamic-toxicokinetic inferences from the general unified threshold (GUTS) model, biomarker responses and molecular docking predictions

We investigated the potential ecological risks and harm to aquatic organisms posed by anionic surfactants such as α-olefin sulfonate (AOS), which are commonly found in industrial and consumer products, including detergents. This study assessed acute (96-h) and subchronic (14-day) responses using antioxidant activity, protein levels, and histopathological changes in Tubifex tubifex exposed to different AOS concentrations (10% of the LC50, 20% of the LC50, and a control). Molecular docking was used to investigate the potential interactions between the key stress biomarker enzymes (superoxide dismutase, catalase, and cytochrome c oxidase) of Tubifex tubifex. Acute AOS exposure showed a concentration-dependent decrease in survival, and the general unified threshold (GUTS) model revealed that survivorship is linked to individual response patterns rather than random (stochastic) fluctuations. The GUTS model also revealed dose-dependent toxicity patterns in Tubifex tubifex exposed to α-olefin sulfonate (AOS), with adaptive mechanisms at lower concentrations but significant increases in mortality beyond a certain threshold, emphasizing the role of the AOS concentration in shaping its toxicological impact. Exposure to AOS disrupted antioxidant activity, inducing oxidative stress, with GST and GPx showing positive associations with surfactant concentration and increased lipid peroxidation (elevated MDA levels); moreover, AOS exposure decreased protein concentration, signifying disturbances in vital cellular processes. Histopathological examinations revealed various tissue-level alterations, including cellular vacuolation, cytoplasmic swelling, inflammation, necrosis, and apoptosis. Molecular docking analysis demonstrated interactions between AOS and enzymes (-catalase, superoxide dismutase, and cytochrome c oxidase) in Tubifex tubifex, including hydrophobic and hydrogen bond interactions, with the potential to disrupt enzyme structures and activities, leading to cellular process disruptions, oxidative stress, and tissue damage. According to the species sensitivity distribution (SSD), the difference in toxicity between Tilapia melanopleura (higher sensitivity) and Daphnia magna (low sensitivity) to AOS suggests distinct toxicokinetic and toxicodynamic mechanisms attributable to more complex physiology in Tilapia and efficient detoxification in Daphnia due to its smaller size.

Optimization and degradation studies of cellulose transesterification to palmitate esters in superbase ionic liquid

Cellulose palmitates (CPs) were synthesized with varying degrees of substitution (DS) via a catalyst-free, homogeneous transesterification of cellulose in a novel superbase ionic liquid (SB-IL) system, specifically 5-methyl-1,5,7-triaza-bicyclo[4.3.0]non-6-enium acetate [mTBNH][OAc], combined with dimethyl sulfoxide (DMSO) as a co-solvent, using vinyl palmitate as the acylating agent. We examined the influence of reaction temperature, reaction time, and the molar ratio of vinyl palmitate to anhydroglucose unit (AGU) on the DS, which ranged from 0.5 to 2.3 under the given conditions. Notably, the reaction order of the three hydroxy groups was C6-OH > C2-OH > C3-OH. To elucidate the chemical structure of CPs and confirm the transesterification process, various spectroscopic techniques including 1H nuclear magnetic resonance (NMR), 13C NMR, heteronuclear single quantum correlation (HSQC), and solid-state NMR were employed. Higher reaction temperatures and extended reaction times led to a decrease in the DS of CPs, potentially due to the degradation of some of the involved chemicals during the transesterification process. We also investigated the stability of the pure ionic liquid (IL) and the IL + DMSO solvent system at elevated temperatures by heating them at 100 °C for 5 h, confirming their chemical integrity through 1H NMR analysis. Additionally, we assessed the compatibility between the solvent system and cellulose by subjecting a mixture of cellulose and the solvent system to 100 °C for 5 h. To compare the structures of untreated cellulose and regenerated cellulose, Fourier transform infrared (FT-IR) spectroscopy was employed. Furthermore, we determined the molar mass of both untreated cellulose and regenerated cellulose, as well as CPs synthesized at higher reaction temperatures and longer durations, using intrinsic viscosity measurements. Lastly, we examined the solubility properties of CPs.

How does ultrasound-assisted ionic liquid treatment affect protein? A comprehensive review of their potential mechanisms, safety evaluation, and physicochemical and functional properties

Proteins are essential to human health with enormous food applications. Despite their advantages, plant and animal proteins often exhibit limited molecular flexibility and poor solubility due to hydrogen bonds, hydrophobic interactions, and ionic interactions within their molecular structures. Thus, there is an urgent need to modify the rigid structure of proteins to enhance their stability and functional properties. Ultrasound-assisted ionic liquid (UA-IL) treatment for developing compound modification and producing proteins with excellent functional properties has received interest. However, no review specifically addresses the interactions between UA-ILs and proteins. Hence, this review focused on recent research advancements concerning the effects and potential reaction mechanisms of UA-ILs on the physicochemical properties (including particle size; primary, secondary, and tertiary structure; and surface morphology) as well as the functionality (such as solubility, emulsifying properties, and foaming ability) of proteins. Moreover, the safety evaluation of modified proteins was also discussed from various perspectives, such as acute and chronic toxicity, genotoxicity, cytotoxicity, and environmental and microbial toxicity. This review demonstrated that UA-IL treatment-induced protein structural changes significantly impact the functional characteristics of proteins. This treatment approach efficiently promotes protein structure stretching and spatial rearrangement through cavitation, thermal effects, and ionic interactions. As a result, the functional properties of modified proteins exhibited an obvious enhancement, thereby bringing more opportunities to utilize modified protein products in the food industry. Potential future directions for protein modification using UA-ILs were also proposed.

Ionic liquids meet lipid bilayers: a state-of-the-art review

In the past 25 years, a vast family of complex organic salts known as room-temperature ionic liquids (ILs) has received increasing attention due to their potential applications. ILs are composed by an organic cation and either an organic or inorganic anion, and possess several intriguing properties such as low vapor pressure and being liquid around room temperature. Several biological studies flagged their moderate-to-high (cyto)-toxicity. Toxicity is, however, also a synonym of affinity, and this boosted a series of biophysical and chemical-physical investigations aimed at exploiting ILs in bio-nanomedicine, drug-delivery, pharmacology, and bio-nanotechnology. Several of these investigations focused on the interaction between ILs and lipid membranes, aimed at determining the microscopic mechanisms behind their interaction. This is the focus of this review work. These studies have been carried out on a variety of different lipid bilayer systems ranging from 1-lipid to 5-lipids systems, and also on cell-extracted membranes. They have been carried out at different chemical-physical conditions and by the use of a number of different approaches, including atomic force microscopy, neutron and X-ray scattering, dynamic light scattering, differential scanning calorimetry, surface quartz microbalance, nuclear magnetic resonance, confocal fluorescence microscopy, and molecular dynamics simulations. The aim of this "2023 Michèle Auger Award" review work is to provide the reader with an up-to-date overview of this fascinating research field where "ILs meet lipid bilayers (aka biomembranes)," with the aim to boost it further and expand its cross-disciplinary edges towards novel high-impact ideas/applications in pharmacology, drug delivery, biomedicine, and bio-nanotechnology.

Anion Effect on Forward Osmosis Performance of Tetrabutylphosphonium-Based Draw Solute Having a Lower Critical Solution Temperature

The applicability of ionic liquids (ILs) as the draw solute in a forward osmosis (FO) system was investigated through a study on the effect of the structural change of the anion on the FO performance. This study evaluated ILs composed of tetrabutylphosphonium cation ([P₄₄₄₄]⁺) and benzenesulfonate anion ([BS]^-), para-position alkyl-substituted benzenesulfonate anions (p-methylbenzenesulfonate ([MBS]^-) and p-ethylbenzenesulfonate ([EBS^-]), and methanesulfonate anion ([MS]^-). The analysis of the thermo-responsive properties suggested that the [P₄₄₄₄][MBS] and [P₄₄₄₄][EBS] ILs have lower critical solution temperatures (LCSTs), which play a beneficial role in terms of the reusability of the draw solute from the diluted draw solutions after the water permeation process. At 20 wt% of an aqueous solution, the LCSTs of [P₄₄₄₄][MBS] and [P₄₄₄₄][EBS] were approximately 36 °C and 25 °C, respectively. The water flux and reverse solute flux of the [P₄₄₄₄][MBS] aqueous solution with higher osmolality than [P₄₄₄₄][EBS] were 7.36 LMH and 5.89 gMH in the active-layer facing the draw solution (AL-DS) mode at osmotic pressure of 25 atm (20 wt% solution), respectively. These results indicate that the [P₄₄₄₄]⁺-based ionic structured materials with LCST are practically advantageous for application as draw solutes.

Synthesis and Characterization of Fluorinated Phosphonium Ionic Liquids to Use as New Engineering Solvents

In this work, a set of novel fluorinated ionic liquids (FILs), based on different tetra-alkyl-phosphonium cations with perfluorobutanesulfonate and perfluoropentanoate anions, were synthesized and characterized in order to check their suitability to apply as engineering solvents. Thermophysical and thermal properties were both determined between 293.15 and 353.15 K, and the molecular volumes and free volumes and the coefficients of isobaric thermal expansion were determined from experimental values of refractive index and density. Lastly, the Walden plot was used to evaluate the ionicity of the novel FILs. The cytotoxicity of these compounds was also determined using the human hepatocellular carcinoma cells (HepG2) and the human colon carcinoma cells (Caco-2). Finally, the results were all discussed with the aim of understanding the behaviour of these compounds, considering the influence of the anion and the hydrogenated alkyl chain length. In summary, the new FILs synthesized in this work present adequate properties for their application in different industrial processes. Most of these compounds are liquid at room temperature with high decomposition temperatures. All phosphonium-based FILs have lower densities than conventional ionic liquids and common organic solvents, and the viscosity depends directly on the selected anion. Furthermore, the ionicity of FILs based on the sulfonate anion is higher than those based on the carboxylate anion. Finally, the phosphonium-based FILs have no significant effect on cellular viability at lower concentrations.

Liquid Systems Based on Tetra(n-butyl)phosphonium Acetate for the Non-dissolving Pretreatment of a Microcrystalline Cellulose (Avicel PH-101)

A non-dissolving pretreatment consisting in the direct contact of cellulose and the ionic liquid tetra(n-butyl)phosphonium acetate, or its fluid mixtures with other phosphonium ionic liquids or with molecular liquids such as ethanol or DMSO, causes a reduction in the crystallinity of the popular microcrystalline cellulose-type Avicel PH-101 under mild conditions. At the same time, the degree of polymerization and the thermal stability of the pretreated Avicel remain essentially unaltered with respect to the untreated Avicel. The diminution of the crystallinity has been related to the increase of the reactivity of the pretreated Avicel samples via analysis of the kinetics of their enzymatic hydrolysis. For selected samples, this improved reactivity has been confirmed through their effective carboxymethylation under a simplified and milder reaction procedure.

Thermo-reversible cellulose micro phase-separation in mixtures of methyltributylphosphonium acetate and γ-valerolactone or DMSO

We have identified cellulose solvents, comprised of binary mixtures of molecular solvents and ionic liquids that rapidly dissolve cellulose to high concentration and show upper‐critical solution temperature (UCST)‐like thermodynamic behaviour ‐ upon cooling and micro phase‐separation to roughly spherical microparticle particle‐gel mixtures. This is a result of an entropy‐dominant process, controllable by changing temperature, with an overall exothermic regeneration step. However, the initial dissolution of cellulose in this system, from the majority cellulose I allomorph upon increasing temperature, is also exothermic. The mixtures essentially act as ‘thermo‐switchable’ gels. Upon initial dissolution and cooling, micro‐scaled spherical particles are formed, the formation onset and size of which are dependent on the presence of traces of water. Wide‐angle X‐ray scattering (WAXS) and ¹³C cross‐polarisation magic‐angle spinning (CP‐MAS) NMR spectroscopy have identified that the cellulose micro phase‐separates with no remaining cellulose I allomorph and eventually forms a proportion of the cellulose II allomorph after water washing and drying. The rheological properties of these solutions demonstrate the possibility of a new type of cellulose processing, whereby morphology can be influenced by changing temperature.

Comprehensive Interrogation on Acetylcholinesterase Inhibition by Ionic Liquids Using Machine Learning and Molecular Modeling

Quantitative structure-activity relationship (QSAR) modeling can be used to predict the toxicity of ionic liquids (ILs), but most QSAR models have been constructed by arbitrarily selecting one machine learning method and ignored the overall interactions between ILs and biological systems, such as proteins. In order to obtain more reliable and interpretable QSAR models and reveal the related molecular mechanism, we performed a systematic analysis of acetylcholinesterase (AChE) inhibition by 153 ILs using machine learning and molecular modeling. Our results showed that more reliable and stable QSAR models (R² > 0.85 for both cross-validation and external validation) were obtained by combining the results from multiple machine learning approaches. In addition, molecular docking results revealed that the cations and organic anions of ILs bound to specific amino acid residues of AChE through noncovalent interactions such as π interactions and hydrogen bonds. The calculation results of binding free energy showed that an electrostatic interaction (ΔE_ele < -285 kJ/mol) was the main driving force for the binding of ILs to AChE. The overall findings from this investigation demonstrate that a systematic approach is much more convincing. Future research in this direction will help design the next generation of biosafe ILs.

Ionic Liquid-Based Materials for Biomedical Applications

Ionic liquids (ILs) have been extensively explored and implemented in different areas, ranging from sensors and actuators to the biomedical field. The increasing attention devoted to ILs centers on their unique properties and possible combination of different cations and anions, allowing the development of materials with specific functionalities and requirements for applications. Particularly for biomedical applications, ILs have been used for biomaterials preparation, improving dissolution and processability, and have been combined with natural and synthetic polymer matrixes to develop IL-polymer hybrid materials to be employed in different fields of the biomedical area. This review focus on recent advances concerning the role of ILs in the development of biomaterials and their combination with natural and synthetic polymers for different biomedical areas, including drug delivery, cancer therapy, tissue engineering, antimicrobial and antifungal agents, and biosensing.

Complex coacervates as extraction media

Various solvents such as ionic liquids, deep eutectic solvents, and aqueous two phase systems have been suggested as greener alternatives to existing extraction processes. We propose to add macroscopic complex coacervates to this list. Complex coacervates are liquid-like forms of polyion condensates and consist of a complex of oppositely charged polyions and water. Previous research focussing on the biological significance of these polyion-rich phases has shown that polyion condensates have the ability to extract certain solutes from water and back-extract them by changing parameters such as ionic strength and pH. In this study, we present the distribution coefficients of five commonly used industrial chemicals, namely lactic acid, butanol, and three types of lipase enzymes in poly(ethylenimine)/poly(acrylic acid) complex coacervates. It was found that the distribution coefficients can vary strongly upon variation of tunable parameters such as polyion ratio, ionic strength, polyion and compound concentrations, and temperature. Distribution coefficients ranged from approximately 2 to 50 depending on the tuning of the system parameters. It was also demonstrated that a temperature-swing extraction is possible, with back-extraction of butanol from complex coacervates with a recovery of 21.1%, demonstrating their potential as extraction media.

Synergistic interactions of ionic liquids and antimicrobials improve drug efficacy

Combinations of ionic liquids (ILs) with antimicrobial compounds have been shown to produce synergistic activities in model liposomes. In this study, imidazolium chloride-based ILs with alkyl tail length variations are combined with commercially available, small-molecule antimicrobials to examine the potential for combinatorial and synergistic antimicrobial effects on P. aeruginosa, E. coli, S. aureus, and S. cerevisiae. The effects of these treatments in a human cell culture model indicate the cytotoxic limits of ILs paired with antimicrobials. The analysis of these ILs demonstrates that the length of the alkyl chain on the IL molecule is proportional to both antimicrobial activity and cytotoxicity. Moreover, the ILs which exhibit synergy with small-molecule antibiotics appear to be acting in a membrane permeabilizing manner. Collectively, results from these experiments demonstrate an increase in antimicrobial efficacy with specific IL + antimicrobial combinations on microbial cultures while maintaining low cytotoxicity in a mammalian cell culture model.

New insight into the negative impact of imidazolium-based ionic liquid [C10mim]Cl on Hela cells: From membrane damage to biochemical alterations

As an alternative to volatile organic solvents, ionic liquids (ILs) are known as "green solvents", and widely used in industrial applications. However, due to their high solubility and stability, ILs have tendency to persist in the water environment, thus having potential negative impacts on the aquatic ecosystem. For assessing the environmental risks of ILs, a fundamental understanding of the toxic effects and mechanisms of ILs is needed. Here we evaluated the cytotoxicity of 1-methyl-3-decylimidazolium chloride ([C₁₀mim]Cl) and elucidated the main toxic mechanism of [C₁₀mim]Cl in human cervical carcinoma (Hela) cells. Microstructural analysis revealed that [C₁₀mim]Cl exposure caused the cell membrane breakage, swollen and vacuolated mitochondria, and spherical cytoskeletal structure. Cytotoxicity assays found that [C₁₀mim]Cl exposure increased ROS production, decreased mitochondrial membrane potential, induced cell apoptosis and cell cycle arrest. These results indicated that [C₁₀mim]Cl could induce damage to cellular membrane structure, affect the integrity of cell ultrastructure, cause the oxidative damage and ultimately lead to the inhibition of cell proliferation. Moreover, alterations of biochemical information including the increased ratios of unsaturated fatty acid and carbonyl groups to lipid, and lipid to protein, and the decreased ratios of Amide I to Amide II, and α-helix to β-sheet were observed in [C₁₀mim]Cl treated cells, suggesting that [C₁₀mim]Cl could affect the structure of membrane lipid alkyl chain and cell membrane fluidity, promote the lipid peroxidation and alter the protein secondary structure. The findings from this work demonstrated that membrane structure is the key target, and membrane damage is involved in [C₁₀mim]Cl induced cytotoxicity.

Alkyl chain length affecting uptake of imidazolium based ionic liquids by ryegrass (Lolium perenne L.)

Imidazolium based ionic liquids (ILs) have been extensively used in the various industrial fields, however, the dependence of their structure on toxicity and bioavailability by plants is not clear. Thus, in this study, uptake of imidazolium based ILs with different alkyl chain lengths (e.g., [C₂mim]⁺ and [C₈mim]⁺) by ryegrass and their toxicity to plant growth were investigated. Results show that the two ILs could be removed by ryegrass with high efficiencies, and a higher uptake efficiency and accumulation was observed for [C₂mim]⁺ with shorter chain length compared with that for [C₈mim]⁺. A higher growth inhibition of ryegrass by [C₈mim]⁺ was observed compared with that by [C₂mim]⁺, indicating the long alkyl chain length of ILs had a negative effect on the plant growth. ILs taken up by ryegrass was retained in the roots and their translocation from roots to shoots was restricted. The IL concentration in roots was 0.68 mg/g-fresh weight for [C₂mim]⁺ and 0.08 mg/g- fresh weight for [C₈mim]⁺ when the ryegrass was exposed to 10 mg/L ILs. This study proved that plant assimilation of ILs depended on their alky chain lengths, which would be useful for understanding the fate of ILs with various structures in phytoremediation for ILs-contaminated water.

Ionic Liquids Toxicity-Benefits and Threats

Ionic liquids (ILs) are solvents with salt structures. Typically, they contain organic cations (ammonium, imidazolium, pyridinium, piperidinium or pyrrolidinium), and halogen, fluorinated or organic anions. While ILs are considered to be environmentally-friendly compounds, only a few reasons support this claim. This is because of high thermal stability, and negligible pressure at room temperature which makes them non-volatile, therefore preventing the release of ILs into the atmosphere. The expansion of the range of applications of ILs in many chemical industry fields has led to a growing threat of contamination of the aquatic and terrestrial environments by these compounds. As the possibility of the release of ILs into the environment s grow systematically, there is an increasing and urgent obligation to determine their toxic and antimicrobial influence on the environment. Many bioassays were carried out to evaluate the (eco)toxicity and biodegradability of ILs. Most of them have questioned their "green" features as ILs turned out to be toxic towards organisms from varied trophic levels. Therefore, there is a need for a new biodegradable, less toxic "greener" ILs. This review presents the potential risks to the environment linked to the application of ILs. These are the following: cytotoxicity evaluated by the use of human cells, toxicity manifesting in aqueous and terrestrial environments. The studies proving the relation between structures versus toxicity for ILs with special emphasis on directions suitable for designing safer ILs synthesized from renewable sources are also presented. The representants of a new generation of easily biodegradable ILs derivatives of amino acids, sugars, choline, and bicyclic monoterpene moiety are collected. Some benefits of using ILs in medicine, agriculture, and the bio-processing industry are also presented.

Toxicological evaluation of ionic liquid in a biological functional tissue construct model based on nano-hydroxyapatite/chitosan/gelatin hybrid scaffolds

The application of ionic liquid is attracting more attentions as green replacement for volatile organic solvents. However, the toxic effects and risks of ionic liquid in different biological systems for human health and environment are poorly evaluated. Among all ionic liquids, 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP-type) ionic liquid is still at the early phase of development, and its toxicity remains unclear. In this study, we fabricated a 3D biological functional tissue construct model based on nano-hydroxyapatite, chitosan and gelatin hybrid scaffold and evaluated its toxic effects of [Emim]DEP-type ionic liquid. As a control group, the examination of ionic liquid's toxic effects on the pre-osteoblast cell line (MC3T3-E1) was detected in 2D cultures. The MTT assay showed that [Emim]DEP-type ionic liquid inhibited the proliferation of cells on both 2D cultures and 3D tissue constructs. This effect was correlated with culturing time and concentration, while the IC50 on 3D scaffolds (12,566, 9015, 7896 μg/mL, at 24 h, 48 h and 72 h, respectively) was found significantly higher compared to 2D cultures (3959, 2226, 1884 μg/mL). Flow cytometry analysis and scanning electron microscope demonstrated that when [Emim]DEP-type ionic liquid acted on MC3T3-E1 cells for 48 h, the shape of 2D cells shrank, together with decreased surface adhesion.

Coaxial Spinning of All-Cellulose Systems for Enhanced Toughness: Filaments of Oxidized Nanofibrils Sheathed in Cellulose II Regenerated from a Protic Ionic Liquid

Hydrogels of TEMPO-oxidized nanocellulose were stabilized for dry-jet wet spinning using a shell of cellulose dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium propionate ([DBNH][CO₂Et]), a protic ionic liquid (PIL). Coagulation in an acidic water bath resulted in continuous core-shell filaments (CSFs) that were tough and flexible with an average dry (and wet) toughness of ∼11 (2) MJ·m^-3 and elongation of ∼9 (14) %. The CSF morphology, chemical composition, thermal stability, crystallinity, and bacterial activity were assessed using scanning electron microscopy with energy-dispersive X-ray spectroscopy, liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, pyrolysis gas chromatography-mass spectrometry, wide-angle X-ray scattering, and bacterial cell culturing, respectively. The coaxial wet spinning yields PIL-free systems carrying on the surface the cellulose II polymorph, which not only enhances the toughness of the filaments but facilities their functionalization.

Immobilization of natural lipid biomembranes and their interactions with choline carboxylates. A nanoplasmonic sensing study

The cell membrane is mainly composed of lipid bilayers with inserted proteins and carbohydrates. Lipid bilayers made of purified or synthetic lipids are widely used for estimating the effect of target compounds on cell membranes. However, the composition of such biomimetic membranes is much simpler than the composition of biological membranes. Interactions between compounds and simple composition biomimetic membranes might not demonstrate the effect of target compounds as precisely as membranes with compositions close to real organisms. Therefore, the aim of our study is to construct biomimetic membrane closely mimicking the state of natural membranes. Liposomes were prepared from lipids extracted from L-α-phosphatidylcholine, Escherichia coli, yeast (Saccharomyces cerevisiae) and bovine liver cells through agitation and sonication. They were immobilized onto silicon dioxide (SiO₂) sensor surfaces using N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid buffer with calcium chloride. The biomimetic membranes were successfully immobilized onto the SiO₂ sensor surface and detected by nanoplasmonic sensing. The immobilized membranes were exposed to choline carboxylates. The membrane disruption effect was, as expected, more pronounced with increasing carbohydrate chain length of the carboxylates. The results correlated with the toxicity values determined using Vibrio fischeri bacteria. The yeast extracted lipid membranes had the strongest response to introduction of choline laurate while the bovine liver lipid extracted liposomes were the most sensitive towards the shorter choline carboxylates. This implies that the composition of the cell membrane plays a crucial role upon interaction with choline carboxylates, and underlines the necessity of testing membrane systems of different origin to obtain an overall image of such interactions.

Correlating Lipid Membrane Permeabilities of Imidazolium Ionic Liquids with their Cytotoxicities on Yeast, Bacterial, and Mammalian Cells

Alkyl-imidazolium chloride ionic liquids (ILs) have been broadly studied for biochemical and biomedical technologies. They can permeabilize lipid bilayer membranes and have cytotoxic effects, which makes them targets for drug delivery biomaterials. We assessed the lipid-membrane permeabilities of ILs with increasing alkyl chain lengths from ethyl to octyl groups on large unilamellar vesicles using a trapped-fluorophore fluorescence lifetime-based leakage experiment. Only the most hydrophobic IL, with the octyl chain, permeabilizes vesicles, and the concentration required for permeabilization corresponds to its critical micelle concentration. To correlate the model vesicle studies with biological cells, we quantified the IL permeabilities and cytotoxicities on different cell lines including bacterial, yeast, and ovine blood cells. The IL permeabilities on vesicles strongly correlate with permeabilities and minimum inhibitory concentrations on biological cells. Despite exhibiting a broad range of lipid compositions, the ILs appear to have similar effects on the vesicles and cell membranes.

Dissolution and Hydrolysis of Bleached Kraft Pulp Using Ionic Liquids

Forestry industries in Chile are facing an important challenge-diversifying their products using green technologies. In this study, the potential use of Ionic Liquids (ILs) to dissolve and hydrolyze eucalyptus wood (mix of Eucalyptus nitens and Eucalyptus globulus) kraft pulp was studied. The Bleached Hardwood Kraft Pulp (BHKP) from a Chilean pulp mill was used together with five different ILs: 1-butyl-3-methylimidazolium chloride [bmim][Cl], 1-butyl-3-methylimidazolium acetate [bmim][Ac], 1-butyl-3-methylimidazolium hydrogen sulfate [bmim][HSO4], 1-ethyl-3-methylimidazolium chloride [emim][Cl], 1-ethyl-3-methylimidazolium acetate [emim][Ac]. Experimentally, one vacuum reactor was designed to study the dissolution/hydrolysis process for each ILs; particularly, the cellulose dissolution process using [bmim][Cl] was studied proposing one molecular dynamic model. Experimental characterization using Atomic Force Microscopy, conductometric titration, among other techniques suggest that all ILs are capable of cellulose dissolution at different levels; in some cases, the dissolution evolved to partial hydrolysis appearing cellulose nanocrystals (CNC) in the form of spherical aggregates with a diameter of 40-120 nm. Molecular dynamics simulations showed that the [bmim][Cl] anions tend to interact actively with cellulose sites and water molecules in the dissolution process. The results showed the potential of some ILs to dissolve/hydrolyze the cellulose from Chilean Eucalyptus, maintaining reactive forms.

Solvent Welding and Imprinting Cellulose Nanofiber Films Using Ionic Liquids

Cellulose nanofiber films (CNFF) were treated via a welding process using ionic liquids (ILs). Acid-base-conjugated ILs derived from 1,5-diazabicyclo[4.3.0]non-5-ene [DBN] and 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) were utilized. The removal efficiency of ILs from welded CNFF was assessed using liquid-state nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The mechanical and physical properties of CNFF indicated surface plasticization of CNFF, which improved transparency. Upon treatment, the average CNFF toughness increased by 27%, and the films reached a Young's modulus of ∼5.8 GPa. These first attempts for IL "welding" show promise to tune the surfaces of biobased films, expanding the scope of properties for the production of new biobased materials in a green chemistry context. The results of this work are highly relevant to the fabrication of CNFFs using ionic liquids and related solvents.

Toxicity of imidazoles ionic liquid [C16mim]Cl to HepG2 cells

Ionic liquids have garnered increasing attention due to their capacity for low vapor pressure, lack of flammability, designability, good stability, and as a asubstitute for conventional organic solvents. However, their toxicity to various organisms has caused growing concern in recent years. Our study aims to evaluate the toxicity of 1-hexadecyl-3-methylimidazolium chloride ([C₁₆min]Cl) to human hepatocellular carcinoma (HepG2) cells, including cell viability, genotoxicity, oxidative stress, apoptosis, cell cycle, and apoptosis-related gene expression. Our results with HepG2 cells suggested that [C₁₆min]Cl inhibited cellular growth, decreased cell viability, induced DNA damage and apoptosis, inhibited superoxide dismutase, decreased glutathione content, increased cellular malondialdehyde levels as well as altering the cell cycle. Moreover, the induction of [C₁₆min]Cl altered the transcription of p53, Bax and Bcl-2, which are critical for controlling cell cycles progression and death, which suggests its involvement with cytotoxicity and apoptosis induced by [C₁₆min]Cl in HepG2 cells. Taken together, these results revealed that [C₁₆min]Cl exerted genotoxicity, oxidative stress and induced apoptosis in HepG2 cells; hence, it is not a healthy solvent.

Assessment of the cytotoxicity of ionic liquids on Spodoptera frugiperda 9 (Sf-9) cell lines via in vitro assays

Cytotoxicity studies are important tools for the assessment of the toxicity of ionic liquids (ILs). In the present study, the cytotoxicity of eleven ILs against Spodoptera frugiperda 9 (Sf-9) cell lines were evaluated via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. The effect on cellular morphology, ultrastructural morphology, and nuclear morphology induced by 1-ethyl-3-methylimidazolium bromide ([C₂mim][Br]) was studied via inverted light microscopy observation, acridine orange staining, and transmission electron microscope (TEM) analysis, respectively. The effect on cell DNA fragmentation, cell apoptosis and cell cycle induced by [C₂mim][Br] was also investigated via DNA agarose gel electrophoresis and flow cytometry analysis, respectively. The results showed that the cytotoxic effect of ILs on Sf-9 cells was related to the IL structures, concentrations, and length of exposure. The morphological features of apoptosis induced by [C₂mim][Br] such as cell shrinkage and convolution, apoptotic bodies, pyknosis, and karyorrhesis were observed. All these phenomena confirmed that Sf-9 cells exposed to [C₂mim][Br] died via apoptosis. This study complements the current knowledge about the cytotoxic properties of ILs on insect cells and highlights the mechanism by which ILs kill these cells. Furthermore, it provides a basis for further studies on the future applications of ILs as insecticides.

Thermodynamics of interaction of ionic liquids with lipid monolayer

Understanding the interaction of ionic liquids with cellular membrane becomes utterly important to comprehend the activities of these liquids in living organisms. Lipid monolayer formed at the air-water interface is employed as a model system to follow this interaction by investigating important thermodynamic parameters. The penetration kinetics of the imidazolium-based ionic liquid 1-decyl-3-methylimidazolium tetrafluoroborate ([DMIM][BF4]) into the zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid layer is found to follow the Boltzmann-like equation that reveals the characteristic time constant which is observed to be the function of initial surface pressure. The enthalpy and entropy calculated from temperature-dependent pressure-area isotherms of the monolayer show that the added ionic liquids bring about a disordering effect in the lipid film. The change in Gibbs free energy indicates that an ionic liquid with longer chain has a far greater disordering effect compared to an ionic liquid with shorter chain. The differential scanning calorimetric measurement on a multilamellar vesicle system shows the main phase transition temperature to shift to a lower value, which, again, indicates the disordering effect of the ionic liquid on lipid membrane. All these studies fundamentally point out that, when ionic liquids interact with lipid molecules, the self-assembled structure of a cellular membrane gets perturbed, which may be the mechanism of these molecules having adverse effects on living organisms.

Cholesterol affects the interaction between an ionic liquid and phospholipid vesicles. A study by differential scanning calorimetry and nanoplasmonic sensing

The present work aims at studying the interactions between cholesterol-rich phosphatidylcholine-based lipid vesicles and trioctylmethylphosphonium acetate ([P₈₈₈₁][OAc]), a biomass dissolving ionic liquid (IL). The effect of cholesterol was assayed by using differential scanning calorimetry (DSC) and nanoplasmonic sensing (NPS) measurement techniques. Cholesterol-enriched dipalmitoyl-phosphatidylcholine vesicles were exposed to different concentrations of the IL, and the derived membrane perturbation was monitored by DSC. The calorimetric data could suggest that the binding and infiltration of the IL are delayed in the vesicles containing cholesterol. To clarify our findings, NPS was applied to quantitatively follow the resistance of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine incorporating 0, 10, and 50mol% of cholesterol toward the IL exposure over time. The membrane perturbation induced by different concentrations of IL was found to be a concentration dependent process on cholesterol-free lipid vesicles. Moreover, our results showed that lipid depletion in cholesterol-enriched lipid vesicles is inversely proportional to the increasing amount of cholesterol in the vesicles. These findings support that cholesterol-rich lipid bilayers are less susceptible toward membrane disrupting agents as compared to membranes that do not incorporate any sterols. This probably occurs because cholesterol tightens the phospholipid acyl chain packing of the plasma membranes, increasing their resistance and reducing their permeability.

Room-temperature ionic liquids meet bio-membranes: the state-of-the-art

Room-temperature ionic liquids (RTIL) are a new class of organic salts whose melting temperature falls below the conventional limit of 100 °C. Their low vapor pressure, moreover, has made these ionic compounds the solvents of choice of the so-called green chemistry. For these and other peculiar characteristics, they are increasingly used in industrial applications. However, studies of their interaction with living organisms have highlighted mild to severe health hazards. Since their cytotoxicity shows a positive correlation with their lipophilicity, several chemical-physical studies of their interactions with biomembranes have been carried out in the last few years, aiming to identify the molecular mechanisms behind their toxicity. Cation chain length and anion nature of RTILs have seemed to affect lipophilicity and, in turn, their toxicity. However, the emerging picture raises new questions, points to the need to assess toxicity on a case-by-case basis, but also suggests a potential positive role of RTILs in pharmacology, bio-medicine and bio-nanotechnology. Here, we review this new subject of research, and comment on the future and the potential importance of this emerging field of study.

Synergistic effects of polymyxin and ionic liquids on lipid vesicle membrane stability and aggregation

Ionic liquids (ILs) have been investigated for potential antibacterial and antibiotic applications due to their ability to destabilize and permeabilize the lipid bilayers in cell membranes. Bacterial assays have shown that combining ILs with antibiotics can provide a synergistic enhancement of their antibacterial activities. We have characterized the mechanism by which the conventional ILs 1-butyl-3-methylimidazolium chloride (BMICl) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF₄) enhance the lipid membrane permeabilization of the well-known antibiotic polymyxin B (PMB). We studied the sizes and membrane permeabilities of multilamellar and unilamellar lipid bilayer vesicles in the presence of ILs alone in aqueous solution, PMB alone, and ILs combined together with PMB. Light scattering-based experiments show that vesicle sizes dramatically increase when ILs are combined with PMB, which suggests that the materials combine to synergistically enhance lipid membrane disruption leading to vesicle aggregation. Lipid bilayer leakage experiments using tris (2,2'-bipyridyl) ruthenium (II) (Ru(bpy)₃²⁺) trapped in lipid vesicles, in which the trapped Ru(bpy)₃²⁺ fluorescence lifetime increases when it leaks out of the vesicle, show that combining BMIBF₄ and PMB together permeabilize the membrane significantly more than with PMB or the IL alone. This demonstrates that ILs can assist in antibiotic permeabilization of lipid bilayers which could explain the increased antibiotic activities in the presence of ILs in solution.

Unraveling Interactions between Ionic Liquids and Phospholipid Vesicles Using Nanoplasmonic Sensing

Owing to their unique properties and unlimited structural combinations, the ubiquitous use of ionic liquids (ILs) is steadily increasing. The objective of the present work is to shed light onto the effects of amidinium- and phosphonium-based ILs on phospholipid vesicles using a nanoplasmonic sensing measurement technique. A new and relatively simple method was developed for the immobilization of large unilamellar vesicles on two different hydrophilic surfaces composed of titanium dioxide and silicon nitride nanolayers. Among the pretreatment conditions studied, vesicle attachment on both substrate materials was achieved with HEPES buffer in the presence of sodium hydroxide and calcium chloride. To get an understanding of how ILs interact with intact vesicles or with supported lipid bilayers, the ILs 1,5-diazabicyclo(4.3.0)non-5-enium acetate ([DBNH][OAc]), tributyl(tetradecyl)phosphonium acetate ([P₁₄₄₄₄][OAc]), and tributylmethylphosphonium acetate ([P₄₄₄₁][OAc]) were introduced into the biomimetic system, and the characteristics of their interactions with the immobilized vesicles were determined. Depending on the IL, in situ real-time IL binding and/or phospholipid removal processes were observed. Although [DBNH][OAc] did not have any significant effect on the phospholipid vesicles, the strongest and the most significant effect was observed with [P₁₄₄₄₄][OAc]. The latter caused clear changes in the phospholipid bilayer: the ILs interacted with the bilayers, resulting in deformation of the vesicles most probably due to the formation of vesicle-IL aggregates. Only a mild effect was observed when [P₄₄₄₁][OAc], at a very high concentration, was exposed to the intact vesicles. In general, these results led to new insights into the effects of ILs on phospholipid vesicles, which are of great importance to the overall understanding of the harmfulness of ILs on biomembranes and biomimicking systems. In addition, the present work highlights the pivotal role of this highly surface-sensitive indirect biosensing technique in scrutinizing and dissecting the integrity and architecture of phospholipid vesicles in the nanoscale range.

Highly water soluble room temperature superionic liquids of APIs

Herein a straightforward approach for the enhancement of the water solubility of common antibiotic and NSAID active pharmaceutical ingredients (APIs) is presented.

Efficiency of hydrophobic phosphonium ionic liquids and DMSO as recyclable cellulose dissolution and regeneration media

Hydrophobic, long-chain tetraalkylphosphonium acetate salts (ionic liquids) were combined with DMSO and the feasibility of these solvent systems for cellulose dissolution and regeneration was studied.

Speciation of indium(iii) chloro complexes in the solvent extraction process from chloride aqueous solutions to ionic liquids

Indium(iii) exists as octahedral mixed complexes, [In(H₂O)_6−nCl_n]³⁻ⁿ (0 ≤ n ≤ 6), in acidic chloride media. After extraction, only the tetrahedral [InCl₄]⁻ complex is present in the ionic liquid phase.

Efficacy of ionic liquids on the growth and simultaneous xylanase production by Sporotrichum thermophile: membrane integrity, composition and morphological investigation

Ionic liquids (ILs) are emerging as promising solvent systems for carrying out various biochemical reactions.

Ultraviolet-Visible (UV-Vis) and Fluorescence Spectroscopic Investigation of the Interactions of Ionic Liquids and Catalase

The inhibitory effects of nine ionic liquids (ILs) on the catalase activity were investigated using fluorescence, absorption ultraviolet-visible spectroscopy. The interactions of ILs and catalase on the molecular level were studied. The experimental results indicated that ILs could inhibit the catalase activity and their inhibitory abilities depended on their chemical structures. Fluorescence experiments showed that hydrogen bonding played an important role in the interaction process. The inhibitory abilities of ILs on catalase activity could be simply described by their hydrophobicity and hydrogen bonding abilities. Unexpected less inhibitory effects of trifluoromethanesulfonate (TfO^-) might be ascribed to its larger size, which makes it difficult to go through the substrate channel of catalase to the active site.

Interactions of Aqueous Imidazolium-Based Ionic Liquid Mixtures with Solid-Supported Phospholipid Vesicles

Despite the environmentally friendly reputation of ionic liquids (ILs), their safety has been recently questioned given their potential as cytotoxic agents. The fundamental mechanisms underlying the interactions between ILs and cells are less studied and by far not completely understood. Biomimetic films are here important biophysical model systems to elucidate fundamental aspects and mechanisms relevant for a large range of biological interaction ranging from signaling to drug reception or toxicity. Here we use dissipative quartz crystal microbalance QCM-D to examine the effect of aqueous imidazolium-based ionic liquid mixtures on solid-supported biomimetic membranes. Specifically, we assess in real time the effect of the cation chain length and the anion nature on a supported vesicle layer of the model phospholipid DMPC. Results indicate that interactions are mainly driven by the hydrophobic components of the IL, which significantly distort the layer and promote vesicle rupture. Our analyses evidence the gradual decrease of the main phase transition temperature upon increasing IL concentration, reflecting increased disorder by weakening of lipid chain interactions. The degree of rupture is significant for ILs with long hydrophobic cation chains and large hydrophobic anions whose behavior is reminiscent of that of antimicrobial peptides.

Extraction and Esterification of Low-Titer Short-Chain Volatile Fatty Acids from Anaerobic Fermentation with Ionic Liquids

Ionic liquids can both act as a solvent and mediate esterification to valorize low-titer volatile fatty acids and generate organic solvents from renewable carbon sources including biowaste and CO2 . In this study, four phosphonium ionic liquids were tested for single-stage extraction of acetic acid from a dilute stream and esterification to ethyl acetate with added ethanol and heat. The esterification proceeded with a maximum conversion of 85.9±1.3 % after 30 min at 75 °C at a 1:1 stoichiometric ratio of reactants. Extraction and esterification can be tailored using mixed-anion ionic liquids; this is demonstrated herein using a common trihexyl(tetradecyl)phosphonium cation and a mixed chloride and bis(trifluoromethylsulfonyl)imide anion ionic liquid. As a further proof-of-concept, ethyl acetate was generated from an ionic liquid-driven esterification of an acetic acid extractant generated using CO2 as the only carbon source by microbial electrosynthesis.

Hormetic effect and mechanism of imidazolium-based ionic liquids on the nematode Caenorhabditis elegans

In the present study, we used Caenorhabditis elegans assay system to investigate in hormetic effects of imidazolium-based bromide Ionic Liquids (ILs) and explored the possible underlying mechanism. Firstly, C. elegans was treated with ILs with different alkyl chain lengths at different concentrations. We found that exposure to ILs at 0.01 mg/L extended the mean lifespan of C. elegans and the ILs with longer alkyl chain showed more obvious effects. To investigate the possible mechanism, the nematodes were exposed to the three ILs at 0.01 mg/L for 2, 5, 7, 9 and 11 days. The levels of reactive oxygen species (ROS) in C. elegans increased significantly when treated for 2 days and then declined gradually compared to those of respective controls as time went on. After exposure for 11 days, the ROS levels and liposuscin accumulation were significantly lower in the treated groups than those of control group. Meanwhile, the expression of aging-related genes sod-5 and daf-16 were both massively up-regulated for the three ILs examined. Our results show that low concentration of ILs exert hormetic effect on C. elegans. ROS generation and expression of aging-related genes may play important roles in the IL-induced hormetic effect on C. elegans.

Effect of Ionic Liquids on Zebrafish (Danio rerio) Viability, Behavior, and Histology; Correlation between Toxicity and Ionic Liquid Aggregation

The effect of 11 common amidinium, imidazolium, and phosphonium based ionic liquids (ILs) on zebrafish (Danio rerio) and Chinese hamster ovary cells (CHO) was investigated with specific emphasis on the effect of anion and cation chain length and aggregation of phosphonium based ILs. Viability and behavioral alteration in the locomotor activity and place preference, after IL treatment of 5 days postfertilization larvae, was recorded. Behavior and histological damage evaluation was performed for adult fish in order to get insight into the long-term effects of two potential biomass-dissolving ILs, [DBNH][OAc] and [P4441][OAc]. To get an understanding of how IL aggregation is linked to the toxicity of ILs, median effective concentrations (EC50) and critical micelle concentrations (CMC) were determined. The long-chain ILs were significantly more toxic than the short-chain ones, and the anion chain length was shown to be less significant than the cation chain length when assessing the impact of ILs on the viability of the organisms. Furthermore, most of the ILs were as monomers when the EC50 was reached. In addition, the ILs used in the long-term tests showed no significant effect on the zebrafish behavior, breeding, or histology, within the used concentration range.