Toxicity of various anions associated with methoxyethyl methyl imidazolium-based ionic liquids on Clostridium sp

Rhodobacter sphaeroides as a model to study the ecotoxicity of 1-alkyl-3-methylimidazolium bromide

The purple non-sulfur bacterium Rhodobacter sphaeroides was selected as a biological model to investigate its response to the toxicity of 1-alkyl-3-methylimidazolium bromide ([C_nmim]Br), a type of ionic liquid (IL), with different alkyl chain lengths (n describes the number of carbon atoms in the alkyl chain). The inhibition of bacterial growth by [C_nmim]Br was positively correlated with n. Morphological characterization revealed that [C_nmim]Br caused cell membrane perforation. The signal amplitude of the electrochromic absorption band shift of endogenous carotenoids showed a negatively linear correlation with n, and the amplitude of the blue-shift of the B850 band in light-harvesting complex 2 showed a positively linear correlation with n. Furthermore, an increase in blocked ATP synthesis and increase in antioxidant enzyme activity were observed in chromatophores treated with ILs containing longer alkyl chains. In summary, the purple bacterium can be developed as a model to monitor ecotoxicity and examine the mechanism of IL toxicity.

Biosafety-inspired structural optimization of triazolium ionic liquids based on structure-toxicity relationships

Ionic liquids (ILs), owing to their low vapor pressure and excellent solvating ability, are being increasingly applied in various industries to replace highly toxic organic solvents. They mainly pollute aquatic environment and soils, directly endangering eco-environment and human health. Therefore, it is critical to understand and optimize structural motifs of ILs with reduced toxicity. Considering human oral exposure is the major route, our investigations employed a human cell panel (modeling oral exposures) including human stomach (GES-1), intestinal (FHC), liver (HepG2) and kidney (HEK293) cells using a series of experimental and computational approaches to explore the cytotoxicity and molecular mechanism of ILs. We discovered that the cytotoxicity of triazolium and imidazolium ILs was human cell line-dependent with cytotoxicity in an order of FHC > GES-1 > HepG2 > HEK293. For this reason, a toxicity assay using a single cell line was highly inappropriate. Compared to anions (Br^-, OTs^-, OTMBS^-) we tested, the cation of ILs played a major role in causing cytotoxicity. Ionic liquids with cations having longer hydrophobic sidechains (IL09 vs. IL01) readily insert into cell membranes with enhanced membrane and lipidomic perturbations, induce cytotoxicity by triggering cell cycle arrest and apoptosis. Reducing sidechain length and incorporating three nitrogen atoms (triazolium) instead of two (imidazolium) in the cation core alleviated cytotoxicity by reducing cell membrane perturbations and cell function interference. These findings provide important guiding principles for the design of the next-generation of "green" and safe ILs.

Emerging impacts of ionic liquids on eco-environmental safety and human health

Owing to their unique physicochemical properties, ionic liquids (ILs) have been rapidly applied in diverse areas, such as organic synthesis, electrochemistry, analytical chemistry, functional materials, pharmaceutics, and biomedicine. The increase in the production and application of ILs has resulted in their release into aquatic and terrestrial environments. Because of their low vapor pressure, ILs cause very little pollution in the atmosphere compared to organic solvents. However, ILs are highly persistent in aquatic and terrestrial environments due to their stability, and therefore, potentially threaten the safety of eco-environments and human health. Specifically, the environmental translocation and retention of ILs, or their accumulation in organisms, are all related to their physiochemical properties, such as hydrophobicity. Based on results of ecotoxicity, cytotoxicity, and toxicity in mammalian models, the mechanisms involved in IL-induced toxicity include damage of cell membranes and induction of oxidative stress. Recently, artificial intelligence and machine learning techniques have been used in mining and modeling toxicity data to make meaningful predictions. Major future challenges are also discussed. This review will accelerate our understanding of the safety issues of ILs and serve as a guideline for the design of the next generation of ILs.

Review of the toxic effects of ionic liquids

Interest in ionic liquids (ILs), called green or designer solvents, has been increasing because of their excellent properties such as thermal stability and low vapor pressure; thus, they can replace harmful organic chemicals and help several industrial fields e.g., energy-storage materials production and biomaterial pretreatment. However, the claim that ILs are green solvents should be carefully considered from an environmental perspective. ILs, given their minimal vapor pressure, may not directly cause atmospheric pollution. However, they have the potential to cause adverse effects if leaked into the environment, for instance if they are spilled due to human mistakes or technical errors. To estimate the risks of ILs, numerous ILs have had their toxicity assessed toward several micro- and macro-organisms over the past few decades. Since the toxic effects of ILs depend on the method of estimating toxicity, it is necessary to briefly summarize and comprehensively discuss the biological effects of ILs according to their structure and toxicity testing levels. This can help simplify our understanding of the toxicity of ILs. Therefore, in this review, we discuss the key findings of toxicological information of ILs, collect some toxicity data of ILs to different species, and explain the influence of IL structure on their toxic properties. In the discussion, we estimated two different sensitivity values of toxicity testing levels depending on the experiment condition, which are theoretical magnitudes of the inherent sensitivity of toxicity testing levels in various conditions and their changes in biological response according to the change in IL structure. Finally, some perspectives, future research directions, and limitations to toxicological research of ILs, presented so far, are discussed.

Ionic liquids and deep eutectic solvents for the recovery of phenolic compounds: effect of ionic liquids structure and process parameters

Water pollution is a severe and challenging issue threatening the sustainable development of human civilization. Besides other pollutants, waste fluid streams contain phenolic compounds. These have an adverse effect on the human health and marine ecosystem due to their toxic, mutagenic, and carcinogenic nature. Therefore, it is necessary to remove such phenolic pollutants from waste stream fluids prior to discharging to the environment. Different methods have been proposed to remove phenolic compounds from wastewater, including extraction using ionic liquids (ILs) and deep eutectic solvent (DES), a class of organic salts having melting point below 100 °C and tunable physicochemical properties. The purpose of this review is to present the progress in utilizing ILs and DES for phenolic compound extraction from waste fluid streams. The effects of IL structural characteristics, such as anion type, cation type, alkyl chain length, and functional groups will be discussed. In addition, the impact of key process parameters such as pH, phenol concentration, phase ratio, and temperature will be also described. More importantly, several ideas for addressing the limitations of the treatment process and improving its efficiency and industrial viability will be presented. These ideas may form the basis for future studies on developing more effective IL-based processes for treating wastewaters contaminated with phenolic pollutants, to address a growing worldwide environmental problem.

Effects of amino acid ionic liquids with different cations ([N2Py], [N2222], [P2222], and [C2mim]) on wheat seedlings

The ecotoxicity of four ionic liquids with different cations (N-ethyl-pyridine alanine [N2Py][Ala], tetraethyl phosphine l-α-amino propionic acid salt [P2222][Ala], 1-ethyl-3-methyl-imidazolium alanine [C2mim][Ala], and tetraethyl ammonium l-α-amino propionic acid salt [N2222][Ala]) was assessed in hydroponically-grown wheat seedlings at concentrations from 200-1200 mg L-1. The results showed that type of cation has a significant influence on the growth, chlorophyll and nutrient uptake of wheat seedlings (P < 0.05). We observed decreased dry weight and shorter roots and shoots in the treated seedlings with increasing IL concentrations. The contents of Chl a and Chl b in wheat seedlings exposed to ILs showed the trend of firstly increasing followed by a decrease with increasing IL concentrations, but they peaked at different concentrations of ILs. In addition, the exposure of wheat seedling to ILs containing different cations (200-1200 mg L-1) led to first an increase and then a decrease of nitrogen content, and reduced the content of phosphorus and potassium. Moreover, the cellular structures, including nuclei, mitochondria, chloroplasts, cell membranes, and the cell walls of wheat leaf and root were affected to varying degrees by 600 mg L-1 ILs. The negative impacts of ILs on wheat seedlings ranked from high to low were: [N2Py][Ala] > [N2222][Ala] > [P2222][Ala] > [C2mim][Ala]. In this work, the relatively stronger toxicity of [N2Py][Ala] was likely contributed by ethanol, which was used to dissolve [N2Py][Ala]. Therefore, it is not recommended to use N-ethyl-pyridine alanine ([N2Py][Ala]) widely in practical applications.

Designing Materials for Aqueous Catalysis: Ionic Liquid Gel and Silica Sphere Entrapped Iron-TAML Catalysts for Oxidative Degradation of Dyes

Materials have been developed that encapsulate a homogeneous catalyst and enable it to operate as a heterogeneous catalyst in water. A hydrophobic ionic liquid within the material was used to dissolve Fe-TAML and keep it from leaching into the aqueous phase. One-pot processes were used to entrap Fe-TAML in basic ionic liquid gels, and ionic liquid gel spheres structured via a modified Stöber synthesis forming SiO₂ particles of uniform size. Catalytic activity was demonstrated via the oxidative degradation of dyes. Fe-TAML entrapped in a basic ionic liquid gel exhibited consistent activity in five recycles. This discovery of heterogenized H₂O₂ activators prepared by sol-gel and Stöber processes opens new possibilities for the creation of engineered catalytic materials for water purification.

Using a freshwater green alga Chlorella pyrenoidosa to evaluate the biotoxicity of ionic liquids with different cations and anions

With the extensive use of ionic liquids (ILs) in various industrial fields, their potential toxicity to aquatic ecosystem has attracted considerable attention. In this work, biotoxicity of ILs with different cations and anions was evaluated by using a freshwater green alga Chlorella pyrenoidosa. Results showed that 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl), 1-octyl-3-methylimidazolium chloride ([C₈mim]Cl), 1-octyl-3-methylimidazolium nitrate ([C₈mim]NO₃), 1-octyl-3-methylimidazolium tetrafluoroborate ([C₈mim]BF₄), and 1-dodecyl-3-methylimidazolium chloride ([C₁₂mim]Cl) had a significant inhibition on the algal growth with EC₅₀ values of 23.48, 4.72, 3.80, 4.44, and 0.10 mg L^-1 at the 72 h of exposure, respectively. These data suggested that the toxicity of ILs increased with the increase of side alkyl chain length, while anions had little influences on their toxicity to this alga. Moreover, changes in chlorophyll a content and chlorophyll fluorescence parameters (F_v/F_m and Φ_PSII) indicated that the five ILs could damage the photosynthetic system of this alga resulting in the decrease of photosynthetic efficiency. The increased soluble protein content and antioxidase activity could be considered as an active response mechanism of this alga against the exposure of ILs. Content of malondialdehyde (MDA) in this alga increased significantly when it was exposed to ILs, suggesting that reactive oxygen species (ROS) were accumulated in the algal cells, which would cause injury of the algal biofilm and chloroplast. Therefore, results obtained in this work would help to explain the possible underlying toxic mechanisms of ILs to C. pyrenoidosa, and provide a significant theoretical support for assessing the toxicity of ILs to aquatic organisms.

Metal extraction from a deep eutectic solvent, an insight into activities

The solvent extraction of gold, palladium, technetium, indium and rhenium from both mixtures of a deep eutectic solvent with aqueous salt solutions and of two different aqueous salt solutions has been performed. Initially using gold and then the other metals the solvent extraction results were interpreted using an activity coefficient/function equation (specific ion interaction theory). The most important presented result is the addition of a new term to the specific ion interaction theory equation. Using the new model it will be possible to make predictions of the behaviour of a solvent extraction system where one of the liquid phases is a mixture of aqueous salts and the deep eutectic solvent.

Synthesis of new water-soluble ionic liquids and their antibacterial profile against gram-positive and gram-negative bacteria

A series of imidazolium bromide salts (NIM-Br 1a, 1b and 1c) bearing different lengths of alkyl chains were synthesized and theirin vitro antibacterial activities were determined by measuring the minimum inhibitory concentration (MIC) values for Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. In addition, these imidazolium derivatives were also evaluated against biofilm produced by these bacterial strains. All compounds were found to be effective against Gram-positive and Gram-negative bacteria, and also more effective on the S. aureus biofilm production than the others.

In vitro toxicological evaluation of ionic liquids and development of effective bioremediation process for their removal

The present study deals with the cyto-genotoxicological impact of ionic liquids, 1-butyl-3-methylimidazolium bromide, trihexyl tetradecylphosphonium dicyanamide, 1-decyl-3-methylimidazolium tetrafluoroborate, benzyldimethyltetradecylammonium chloride, and 1-butyl-4-methylpyridinium chloride, on animal cells and their biodegradation. The long alkyl chain containing ionic liquids were found to be more toxic whereas benzene functional group in benzyldimethyltetradecylammonium chloride enhances its toxicity. Aerobic bacterial granules, a bacterial consortium, were developed that have promising ability to break down these organic pollutants. These aerobic bacterial granules have been applied for the biodegradation of ionic liquids. The biological oxygen demand (5 days) and chemical oxygen demand parameters confirmed that the biodegradation was solely due to aerobic bacterial granules which further decreased the time period needed for regular biodegradation by biological oxygen demand (28 days). The high resolution mass spectrometry analysis further approved that the degradation of ionic liquids was mainly via removal of the methyl group. Elevated N-demethylase enzyme activity supports the ionic liquids degradation which may be occurring through demethylation mechanism. The amplicon sequencing of aerobic bacterial granules gives insight into the involvement of the bacterial community in the biodegradation process.

Enhanced separation performance of aqueous biphasic systems formed by carbohydrates and tetraalkylphosphonium- or tetraalkylammonium-based ionic liquids

Aiming at establishing more effective and sustainable separation processes, herein we propose the use of carbohydrates combined with tetralkylphosphonium- and tetralkylammonium-based ionic liquids (ILs) to form aqueous biphasic systems (ABS). The formation of ABS composed of non-aromatic and non-fluorinated ILs with carbohydrates is here shown for the first time. These novel systems are competive extraction platforms when compared against more conventional ABS formed by ILs and salts or fluorinated ILs and carbohydrates. Finally, it is shown that these systems can be efficiently recovered and reused.

Phytotoxicity of ionic liquids with different structures on wheat seedlings and evaluation of their toxicity attenuation at the presence of modified biochar by adsorption effect

The toxic effects of eight common ionic liquids (ILs) on wheat seedlings was evaluated with specific emphasis on the influence of concentration range, anion species and cation chain length of ILs. The growth of wheat seeds was significantly inhibited by ILs, especially under higher concentration, presence of the fluoride anion and the longer alkyl chain length of the cation. The modified biochar (PB-K-N) efficiently removed the ILs from aqueous solutions, the order of the adsorption capacities was as follows: [Bmim]OAc [Bmim]C₇H₅O₂ [Bmim]BF₄ [Bmim]Br, [Domim]Br [BPy]Br [Omim]Br [Bmim]Br [Emim]Br. Furthermore, the wheat growth of all ILs groups except [Bmim]BF₄ group in the presence of PB-K-N was also similar to that of the control groups, which clearly demonstrated that PB-K-N could decrease or alleviate toxicity of ILs toward wheat by adsorption effect. Therefore, the biochar application was effective in improving plant resistance to ILs stress by adsorption, to reduce the phytotoxicity of ILs and provide an alternative approach for the utilization of PB-K-N in ILs contaminated water and soils.

Effect of 1-methyl-3-hexylimidazolium bromide on zebrafish (Danio rerio)

Room-temperature ionic liquids, generally referred to ionic liquids (ILs), are "green solvents". Antioxidant responses and DNA damage in zebrafish livers exposed to 1-methyl-3-hexylimidazolium bromide ([C₆mim]Br) were evaluated at various doses (5-40 mg/L) for a 28-day IL-exposure. A significant decrease of superoxide dismutase (SOD) activity was exhibited, and catalase (CAT) was inhibited at the highest dose (40 mg/L). Reactive oxygen species (ROS) levels were significantly promoted at most exposure interval times except for the dose of 5 mg/L on day 21 in male and days 21 and 28 in female. Malonaldehyde (MDA) contents remarkable increased exposed to [C₆mim]Br. Besides, a notable increase was exhibited, which indicated an inducement of DNA damage with respect to control groups. Thus, we believed that [C₆mim]Br causes oxidative stress and DNA damage in zebrafish. Gender differences were insignificant in almost all the tested biomarkers, thus, male and female zebrafish could be mixed at a ratio of 1:1 in the future evaluation. The present study may also provide basic toxicology information for IL evaluation to aquatic organisms.

Evaluation of risk assessment of new industrial pollutant, ionic liquids on environmental living systems

Ionic liquids (ILs) are much known for their promising alternative for volatile solvents in industries and gained popularity as a greener solvent, however industrial effluent discharge containing ILs are also increasing. There is a scarcity of information on the toxicity of ILs; the present study will explore different facts about their harmfulness. The toxic effects of five different ILs: [C₄MIM]Br, [Hx₃PC₁₄]N(CN)₂, [C₁₀MIM]BF₄, [BTDA]Cl and [C₄MPY]Cl were analysed on bacteria, fungi, plant and animal cells. Both Gram positive and negative bacteria were found to be more susceptible to [C₁₀MIM]BF₄ and [BTDA]Cl than [C₄MIM]Br, [Hx₃PC₁₄]N(CN)₂ and [C₄MPY]Cl, whereas fungi revealed quite a resistance to all ILs. All ILs were toxic towards Triticum aestivum affecting their roots and shoots, however [C₁₀MIM]BF₄ and [BTDA]Cl were more toxic amongst them. Studies on Allium cepa described their toxic behaviour at the genetic level by altering cell division and nuclear material. Furthermore, studies on human red blood cells described by % haemolysis in which [Hx₃PC₁₄]N(CN)₂ and [BTDA]Cl exhibited higher toxicity at very lower concentrations. While the genotoxic effect on blood lymphocytes exerted by [Hx₃PC₁₄]N(CN)₂, [C₁₀MIM]BF₄ and [BTDA]Cl confirmed their toxic effects on human cells.

Enhancement of anaerobic digestion of grass by pretreatment with imidazolium-based ionic liquids

In this work, the toxicity of imidazolium-based ionic liquids (ILs) and the enhancement of high-solid anaerobic digestion by pretreatment were studied. Compared with [Bmim]Cl, [Bmim]OAc and [Bmim]BF₄, [Bmim]PF₆ had the highest toxicity. When the mass ratio of [Bmim]PF₆ to grass was higher than 1:10, biogas was not produced within 30 days. The ability to remove lignin and hemicellulose followed the sequence of [Bmim]OAc, [Bmim]Cl, [Bmim]BF₄ and [Bmim]PF₆. The crystallinity index of grass pretreated with [Bmim]OAc, [Bmim]Cl, [Bmim]BF₄ and [Bmim]PF₆ reduced by 73.83%, 54.44%, 17.52% and 7.47%, respectively. The pretreatment with ILs enhanced the methane yield of grass by reducing crystallinity and particle size. The grass pretreated with [Bmim]OAc had the highest methane yield, about 221 mL/g volatile solids, due to its good lignin removal ability and relative low toxicity. After 10 times recycling, the cumulative methane yield of grass pretreated by recycled [Bmim]OAc decreased by 11.95%.

Environmental Impact of Ionic Liquids: Recent Advances in (Eco)toxicology and (Bio)degradability

This Review aims to integrate the most recent and pertinent data available on the (bio)degradability and toxicity of ionic liquids for global and critical analysis and on the conscious use of these compounds on a large scale thereafter. The integrated data will enable focus on the recognition of toxicophores and on the way the community has been dealing with them, with the aim to obtain greener and safer ionic liquids. Also, an update of the most recent biotic and abiotic methods developed to overcome some of these challenging issues will be presented. The review structure aims to present a potential sequence of events that can occur upon discharging ionic liquids into the environment and the potential long-term consequences.

Potential toxicity of ionic liquid ([C12mim]BF4) on the growth and biochemical characteristics of a marine diatom Phaeodactylum tricornutum

Recently, some researchers have pointed out that the threats of ionic liquids (ILs) to aquatic environment cannot be ignored. Thus, this study investigated the potential toxicity of 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C₁₂mim]BF₄) on a marine diatom Phaeodactylum tricornutum at population, biochemical and physiological levels using 96h growth tests with a batch-culture system. Results showed that [C₁₂mim]BF₄ was very stable in aquatic environment during 96h of exposure. The growth of P. tricornutum was significantly inhibited by [C₁₂mim]BF₄ with 24, 48, 72 and 96h EC₅₀ values of 0.63, 0.61, 0.68 and 0.72mgL^-1, respectively. Although there were no significant differences between the controls and treatments with 0.1 and 0.5mgL^-1 [C₁₂mim]BF₄, the effective quantum yields (Φ_PSII) of the diatom in 1, 2.5, 5 and 10mgL^-1 [C₁₂mim]BF₄ treatments were 61.48, 17.04, 2.96 and 0.74% of that in the controls at 96h of exposure, respectively. Chl a content of the diatom was decreased by 34.86, 47.79, 49.81, 59.21, 79.82 and 86.98% compared with that of the controls at 96h of exposure in 0.1, 0.5, 1, 2.5, 5 and 10mgL^-1 [C₁₂mim]BF₄ treatments, respectively. Relative to the controls, soluble sugar content, reactive oxygen species (ROS) level, malondialdehyde (MDA) content, superoxide dismutase (SOD) and peroxidase (POD) activities of the diatom increased with increasing [C₁₂mim]BF₄ concentrations at 96h of exposure, and reached their maxima (1.46μg10⁶cell^-1, 7.48FU10⁷cell^-1, 3.35nmol10⁸cell^-1, 33.41 and 7.23Umg^-1 proteins, respectively) in 5mgL^-1 [C₁₂mim]BF₄ treatments. While the maximum soluble protein content (1.56μg10⁶cell^-1) of the diatom was obtained in 0.5mgL^-1 [C₁₂mim]BF₄ treatments, and then decreased with increasing [C₁₂mim]BF₄ concentrations from 0.5 to 10mgL^-1. These findings provide strong evidence for the potential toxicity of ILs to marine diatoms.

Assessment of ionic liquids' toxicity through the inhibition of acylase I activity on a microflow system

Acylase I (ACY I) plays a role in the detoxication and bioactivation of xenobiotics as well in other physiological functions. In this context, an automated ACY I assay for the evaluation of ionic liquids' (ILs) toxicity was developed. The assay was implemented in a sequential injection analysis (SIA) system and was applied to eight commercially available ILs. The SIA methodology was based on the deacetylation of N-acetyl-l-methionine with production of l-methionine, which was determined using fluorescamine. ACY I inhibition in the presence of ILs was monitored by the decrease of fluorescence intensity. The obtained results confirmed the influence of ILs' structural elements on its toxicity and revealed that pyridinium and phosphonium cations, longer alkyl side chains and tetrafluoroborate anion displayed higher toxic effect on enzyme activity. The developed methodology proved to be robust and exhibited good repeatability (RSD < 1.3%, n = 10), leading also to a reduction of reagents consumption and effluents production. Thus, it is expected that the proposed assay can be used as a novel tool for ILs' toxicity screening.

Biological Activity of Ionic Liquids and Their Application in Pharmaceutics and Medicine

Ionic liquids are remarkable chemical compounds, which find applications in many areas of modern science. Because of their highly tunable nature and exceptional properties, ionic liquids have become essential players in the fields of synthesis and catalysis, extraction, electrochemistry, analytics, biotechnology, etc. Apart from physical and chemical features of ionic liquids, their high biological activity has been attracting significant attention from biochemists, ecologists, and medical scientists. This Review is dedicated to biological activities of ionic liquids, with a special emphasis on their potential employment in pharmaceutics and medicine. The accumulated data on the biological activity of ionic liquids, including their antimicrobial and cytotoxic properties, are discussed in view of possible applications in drug synthesis and drug delivery systems. Dedicated attention is given to a novel active pharmaceutical ingredient-ionic liquid (API-IL) concept, which suggests using traditional drugs in the form of ionic liquid species. The main aim of this Review is to attract a broad audience of chemical, biological, and medical scientists to study advantages of ionic liquid pharmaceutics. Overall, the discussed data highlight the importance of the research direction defined as "Ioliomics", studies of ions in liquids in modern chemistry, biology, and medicine.

Comparative in vitro study of cholinium-based ionic liquids and deep eutectic solvents toward fish cell line

With the advent of ionic liquids, much was expected concerning their applicability as an alternative to organic solvents in the chemical technology and biotechnology fields. However, the most studied and commonly used ionic liquids based on imidazolium and pyridinium were found not to be as environmentally friendly as it was first expected. Therefore, a new generation of alternative solvents named natural ionic liquids and deep eutectic solvents, composed of natural and/or renewable compounds, have come into focus in recent years. Since the number of newly synthesized chemicals increases yearly, simple and reliable methods for their ecotoxicological assessment are necessary. Permanent fish cell lines can serve as a test system for the evaluation of a chemical's cytotoxicity. This paper presents research results on the cytotoxic effects on Channel Catfish Ovary (CCO) cell line induced by fifteen cholinium-based ionic liquids and deep eutectic solvents. Based on the decrease in cell viability, the most obvious toxic effect on CCO cells was caused by ionic liquid choline oxalate, while other solvents tested exhibited low cytotoxicity. Therefore, we can conclude that cholinium-based ionic liquids and deep eutectic solvents are comparatively less toxic to CCO cells than conventional ionic liquids.

Assessing chemical toxicity of ionic liquids on Vibrio fischeri: Correlation with structure and composition

One of the most important properties of ionic liquids is their non-volatility, making them potentially "green" alternatives to volatile organic compounds. However, they are widely soluble in water, meaning that they can be released into aquatic ecosystems and so contribute to water pollution. Nevertheless, although the toxicity of ILs has been widely assessed in the literature, the information is still scarce due to the great number of ionic liquids that have been synthesized. The present work reports the toxicity of twenty-nine imidazolium-, pyridinium- and ammonium-based ionic liquids towards the bioluminescent photobacterium Vibrio fischeri. When the effect of the type of anion, the length of the alkyl chain of the cation, the cation core and the presence of a functionalized side chain in the cation on ionic liquid toxicity were analyzed, the main influence was seen to be exercised by the alkyl chain length. A Quantitative Structure-Activity Relationships-based method was used to compare the experimental results with previously estimated values and very good agreement was obtained. A relationship between the toxicity, expressed as Log EC50, and the 1-octanol-water partition coefficient was established.

Hormetic effect of ionic liquid 1-ethyl-3-methylimidazolium acetate on bacteria

The biological effect of ionic liquids (ILs) is one of the highly debated topics as they are being contemplated for various industrial applications. 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) showed remarkable hormesis on anaerobic Clostridium sp. and aerobic Pseudomonas putida. Bacterial growth was stimulated at up to 2.5 g L(-1) and inhibited at >2.5 g L(-1) of [EMIM][Ac]. The growth of Clostridium sp. and P. putida were higher by 0.4 and 4-fold respectively, in the presence of 0.5 g L(-1) [EMIM][Ac]. Assessment of the effect of [EMIM][Ac] under different growth conditions showed that the hormesis of [EMIM][Ac] was mediated via regulation of medium pH. Hormetic effect of [EMIM][Ac] was evident only in medium with poor buffering capacity and in the presence of a fermentable substrate as the carbon source. The hormetic effect of [EMIM][Ac] on bacterial growth is most likely associated with the buffering capacity of acetate anion. These observations have implications in ILs toxicity studies and ecological risk assessment.

Toxicity assessment of ionic liquids with Vibrio fischeri: an alternative fully automated methodology

A fully automated Vibrio fischeri methodology based on sequential injection analysis (SIA) has been developed. The methodology was based on the aspiration of 75 μL of bacteria and 50 μL of inhibitor followed by measurement of the luminescence of bacteria. The assays were conducted for contact times of 5, 15, and 30 min, by means of three mixing chambers that ensured adequate mixing conditions. The optimized methodology provided a precise control of the reaction conditions which is an asset for the analysis of a large number of samples. The developed methodology was applied to the evaluation of the impact of a set of ionic liquids (ILs) on V. fischeri and the results were compared with those provided by a conventional assay kit (Biotox(®)). The collected data evidenced the influence of different cation head groups and anion moieties on the toxicity of ILs. Generally, aromatic cations and fluorine-containing anions displayed higher impact on V. fischeri, evidenced by lower EC50. The proposed methodology was validated through statistical analysis which demonstrated a strong positive correlation (P>0.98) between assays. It is expected that the automated methodology can be tested for more classes of compounds and used as alternative to microplate based V. fischeri assay kits.

Antimicrobial effects of short chained imidazolium-based ionic liquids—influence of anion chaotropicity

Ionic liquids (ILs), a new solvent class composed solely of ions, have already found their way into numerous chemical and biochemical applications. Due to their unique properties and wide application range, research utilizing this new technology for biotechnological applications is steadily increasing. However, progress is hampered by lack of toxicological data, especially concerning IL anions and their general underlying toxicity mechanisms. The present study investigated for the first time the influence of the chaotropicity of the anion for nine imidazole based ILs on their antimicrobial behavior. The results indicate that for ILs with small cations ([C(n)mim](+) with n=2 and 4), the chaotropicity of the anion is a major factor regarding antimicrobial behavior, while for [C6mim](+) based ILs a surfactant-like behavior was identified that explains their high toxicity. It could also be shown that with increasing anion chaotropicity the surfactant-like behavior of the cation is strengthened. Identification of chaotropicity as an underlying mode of antimicrobial action of ILs presents a new point of adjustment for future design with regard to their toxicological behavior.

Predictive modeling studies for the ecotoxicity of ionic liquids towards the green algae Scenedesmus vacuolatus

Hazardous potential of ionic liquids is becoming an issue of high concern with increasing application of these compounds in various industrial processes. Predictive toxicological modeling on ionic liquids provides a rational assessment strategy and aids in developing suitable guidance for designing novel analogues. The present study attempts to explore the chemical features of ionic liquids responsible for their ecotoxicity towards the green algae Scenedesmus vacuolatus by developing mathematical models using extended topochemical atom (ETA) indices along with other categories of chemical descriptors. The entire study has been conducted with reference to the OECD guidelines for QSAR model development using predictive classification and regression modeling strategies. The best models from both the analyses showed that ecotoxicity of ionic liquids can be decreased by reducing chain length of cationic substituents and increasing hydrogen bond donor feature in cations, and replacing bulky unsaturated anions with simple saturated moiety having less lipophilic heteroatoms.

Toxicity of ionic liquids to Clostridium sp. and effects on uranium biosorption

As green solvents ionic liquids (ILs) show high potential in nuclear industry for extraction and purification of actinides. However, to date relatively little information has been gained on ILs application in microbial processes, for example biosorption of radionuclides. We investigated the effects of three ILs, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), N-ethylpyridinium trifluoroacetate (EtPyCF3COO) and N-ethylpyridinium tetrafluoroborate (EtPyBF4) on the growth and biosorption of uranium by Clostridium sp. The ILs affected the growth of the bacterium as evidenced by decreases in optical density, total gas production, and organic acids production from glucose metabolism. The IC50-48h of three ILs decreased in the order of BMIMPF6 (8.26mM)>EtPyBF4 (7.04mM)>EtPyCF3COO (4.05mM). Uranium biosorption by the bacterial cells decreased by 75% in the presence of 1% (v/v) BMIMPF6 and by about 90% with 1% (v/v) EtPyBF4 or EtPyCF3COO, in comparison to the control without ILs. The diminished biosorption may be attributed to the membrane damages induced by EtPyBF4 and EtPyCF3COO, which can be visualized by Transmission Electron Microscope (TEM) analysis. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed the accumulation of uranium inside peripheral membrane of the cells exposed to uranium alone or with BMIMPF6, while little or no accumulation was observed in the presence of EtPyBF4 and EtPyCF3COO. These results imply that potential toxicity of ILs towards microorganisms is a particularly important issue in limiting its biotechnological applications.

Toxicity of ionic liquids toward microorganisms interesting to the food industry

Filamentous fungi were resistant to high concentrations of imidazolium-based ionic liquids, andPseudomonas aeruginosawas tolerant to [NTf₂] anions.

Toxicity of various kinds of ionic liquids towards the cell growth and end product formation of the probiotic strain, Propionibacterium freudenreichii

The effect of different concentrations of [HMIM][PTS] on the cell growth ofPropionibacterium freudenreichii.

Evaluation of toxicity and biodegradability of cholinium amino acids ionic liquids

Cholinium amino acid ionic liquids ([Ch][AA] ILs), which are wholly composed of renewable biomaterials, have recently been demonstrated to have very promising properties for applications in organic synthesis and biomass pretreatment. In this work, the toxicity of these ILs toward enzymes and bacteria was assessed, and the effect of the anion on these properties is discussed. The inhibitory potentials of this type of ILs to acetylcholinesterase were weaker approximately an order of magnitude than the traditional IL 1-butyl-3-methylimidazolium tetrafluoroborate. Additionally, the [Ch][AA] ILs displayed low toxicity toward the bacteria tested. Furthermore, the biodegradability of the [Ch][AA] ILs was evaluated via the closed bottle and CO(2) headspace tests using wastewater microorganisms. All the ILs were classified as 'readily biodegradable' based on their high levels of mineralization (62-87%). The presence of extra carboxyl or amide groups on the amino acid side chain rendered the ILs significantly more susceptible to microbial breakdown. In addition, for most of the [Ch][AA] ILs, low toxicity correlated with good biodegradability. The low toxicity and high biodegradability of these novel [Ch][AA] make them promising candidates for use as environmentally friendly solvents in large-scale applications.

APPLICATIONS OF IONIC LIQUIDS IN BIOMEDICINE

(Ionic liquids) ILs have unique properties compared with conventional solvents, opening a wide range of application as solvents and catalysts. ILs' cytotoxicity extend their application in biomedicine by acting as antimicrobial and anticancer agents. This article reviews the current research advances of ILs' biomedical application from the following four aspects: solvents, catalysts, antimicrobial and anticancer agents. By introducing ILs' interesting structures and their corresponding unique properties, this review concludes the current state-of-art of ILs biomedical applications. We also try to point out the ILs issues and solutions for more potential applications in biomedicine.

(Eco)toxicity of fluoro-organic and cyano-based ionic liquid anions

The (eco)toxicity of the most common ionic liquid anions like [N(CN)(2)](-), [C(CN)(3)](-), [B(CN)(4)](-), [(CF(3)SO(2))(2)N](-), [(C(2)F(5))(3)PF(3)](-) was investigated in test systems of different trophic level. In the same order, and thus with increasing hydrophobicity, a trend of higher toxicity was found. Especially the [(C(2)F(5))(3)PF(3)](-) moiety poses a significant hazard towards aquatic organisms.

Ether- and alcohol-functionalized task-specific ionic liquids: attractive properties and applications

In recent years, the designer nature of ionic liquids (ILs) has driven their exploration and exploitation in countless fields among the physical and chemical sciences. A fair measure of the tremendous attention placed on these fluids has been attributed to their inherent designer nature. And yet, there are relatively few examples of reviews that emphasize this vital aspect in an exhaustive or meaningful way. In this critical review, we systematically survey the physicochemical properties of the collective library of ether- and alcohol-functionalized ILs, highlighting the impact of ionic structure on features such as viscosity, phase behavior/transitions, density, thermostability, electrochemical properties, and polarity (e.g. hydrophilicity, hydrogen bonding capability). In the latter portions of this review, we emphasize the attractive applications of these functionalized ILs across a range of disciplines, including their use as electrolytes or functional fluids for electrochemistry, extractions, biphasic systems, gas separations, carbon capture, carbohydrate dissolution (particularly, the (ligno)celluloses), polymer chemistry, antimicrobial and antielectrostatic agents, organic synthesis, biomolecular stabilization and activation, and nanoscience. Finally, this review discusses anion-functionalized ILs, including sulfur- and oxygen-functionalized analogs, as well as choline-based deep eutectic solvents (DESs), an emerging class of fluids which can be sensibly categorized as semi-molecular cousins to the IL. Finally, the toxicity and biodegradability of ether- and alcohol-functionalized ILs are discussed and cautiously evaluated in light of recent reports. By carefully summarizing literature examples on the properties and applications of oxy-functional designer ILs up till now, it is our intent that this review offers a barometer for gauging future advances in the field as well as a trigger to spur further contemplation of these seemingly inexhaustible and--relative to their potential--virtually untouched fluids. It is abundantly clear that these remarkable fluidic materials are here to stay, just as certain design rules are slowly beginning to emerge. However, in fairness, serendipity also still plays an undeniable role, highlighting the need for both expanded in silico studies and a beacon to attract bright, young researchers to the field (406 references).

Development of a novel mathematical model using a group contribution method for prediction of ionic liquid toxicities

A new mathematical model has been developed that expresses the toxicities (EC₅₀ values) of a wide variety of ionic liquids (ILs) towards the freshwater flea Daphnia magna by means of a quantitative structure-activity relationship (QSAR). The data were analyzed using summed contributions from the cations, their alkyl substituents and anions. The model employed multiple linear regression analysis with polynomial model using the MATLAB software. The model predicted IL toxicities with R²=0.974 and standard error of estimate of 0.028. This model affords a practical, cost-effective and convenient alternative to experimental ecotoxicological assessment of many ILs.

Alkyl-methylimidazolium ionic liquids affect the growth and fermentative metabolism of Clostridium sp

In this study, the effect of ionic liquids, 1-ethyl-3-methylimidazolium acetate [EMIM][Ac], 1-ethyl-3-methylimidazolium diethylphosphate [EMIM][DEP], and 1-methyl-3-methylimidazolium dimethylphosphate [MMIM][DMP] on the growth and glucose fermentation of Clostridium sp. was investigated. Among the three ionic liquids tested, [MMIM][DMP] was found to be least toxic. Growth of Clostridium sp. was not inhibited up to 2.5, 4 and 4 g L(-1) of [EMIM][Ac], [EMIM][DEP] and [MMIM][DMP], respectively. [EMIM][Ac] at <2.5 g L(-1), showed hormetic effect and stimulated the growth and fermentation by modulating medium pH. Total organic acid production increased in the presence of 2.5 and 2 g L(-1) of [EMIM][Ac] and [MMIM][DMP]. Ionic liquids had no significant influence on alcohol production at <2.5 g L(-1). Total gas production was affected by ILs at ≥ 2.5 g L(-1) and varied with type of methylimidazolium IL. Overall, the results show that the growth and fermentative metabolism of Clostridium sp. is not impacted by ILs at concentrations below 2.5 g L(-1).