Phytotoxicity of ionic liquids

Ionic-liquid/Carbowax 20 M functionalized capsule phase microextraction platform for the extraction of phosphodiesterase-5 inhibitors from human serum and urine prior to their determination by LC-MS

Capsule phase microextraction (CPME) is an efficient bioanalytical technique that streamlines the sample preparation by integrating the filtration and stirring mechanism directly into the device. A novel composite sorbent designed to be selective towards the target analytes consisting of mixed-mode sorbent chemistry synthesized by sol-gel technology is found promising and superior to the conventional C18 sorbents. Herein we describe the encapsulation of an ionic liquid (IL)/Carbowax 20M-functionalized sol-gel sorbent (sol-gel IL/Carbowax 20 M) in the lumen of porous polypropylene tubes for the capsule phase microextraction of three phosphodiesterase-5 inhibitors namely avanafil, sildenafil, and tadalafil in human serum and urine samples. The CPME device was characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). The experimental parameters of CPME procedure (e.g. sample pH and ionic strength, extraction time, stirring rate, elution solvent and volume) were carefully optimized to achieve the highest possible extraction efficiency for the analytes. Method validation was conducted in terms of precision, linearity, accuracy, matrix effect, lower limits of quantification, and limits of detection (LOD). The method linearity was investigated in the range of 50-1000 ng mL-1 for all analytes while the precision was less than 11.8 % in all cases. For all analytes, the LOD values were 17 ng mL-1. The IL/CW 20M-functionalized microextraction capsules could be reused at least 25 times both for urine and serum samples. The green character and the applicability of the proposed method were evaluated using the ComplexGAPI and BAGI indexes. The optimized CPME protocol exhibited reduced consumption of organic solvent and generation of waste, cost-effectiveness, and simplicity. Finally, the proposed method was successfully applied to the analysis of sildenafil in human urine after administration of drug-containing formulation.

A New 2-Aminospiropyrazolylammonium Cation with Possible Uses in the Topical Areas of Ionic Liquids

Based on the fact that 2-aminospiropyrazolinium compounds and structurally related azoniaspiro compounds belong, in a broad sense, to the class of ionic liquids, we have reviewed them and studied their practical applications. To search for possible uses of a new 2-aminospiropyrazolinium compounds, it is necessary to undertake a comparison with the related class of azoniaspiro compounds based on available information. The structures of the well-studied class of azoniaspiro compounds and the related but little-studied class of 2-aminospiropyrazolinium have rigid frameworks, limited conformational freedom, and a salt nature. These properties give them the ability to organize the nearby molecular space and enable the structure-forming ability of azoniaspiro compounds in the synthesis of zeolites, as well as the ability to act as phase-transfer catalysts and have selective biological effects. Additionally, these characteristics enable their ability to act as electrolytes and serve as materials for anion exchange membranes in fuel cells and water electrolyzers. Thus, the well-studied properties of azoniaspiro compounds as phase-transfer catalysts, structure-directing agents, electrolytes, and materials for membranes in power sources would encourage the study of the similar properties of 2-aminospiropyrazolinium compounds, which we have studied in relation to in vitro antitubercular, antidiabetic, and antimicrobial activities.

Mechanisms of Biological Effects of Ionic Liquids: From Single Cells to Multicellular Organisms

The review presents a detailed discussion of the evolving field studying interactions between ionic liquids (ILs) and biological systems. Originating from molten salt electrolytes to present multiapplication substances, ILs have found usage across various fields due to their exceptional physicochemical properties, including excellent tunability. However, their interactions with biological systems and potential influence on living organisms remain largely unexplored. This review examines the cytotoxic effects of ILs on cell cultures, biomolecules, and vertebrate and invertebrate organisms. Our understanding of IL toxicity, while growing in recent years, is yet nascent. The established findings include correlations between harmful effects of ILs and their ability to disturb cellular membranes, their potential to trigger oxidative stress in cells, and their ability to cause cell death via apoptosis. Future research directions proposed in the review include studying the distribution of various ILs within cellular compartments and organelles, investigating metabolic transformations of ILs in cells and organisms, detailed analysis of IL effects on proteins involved in oxidative stress and apoptosis, correlation studies between IL doses, exposure times and resulting adverse effects, and examination of effects of subtoxic concentrations of ILs on various biological objects. This review aims to serve as a critical analysis of the current body of knowledge on IL-related toxicity mechanisms. Furthermore, it can guide researchers toward the design of less toxic ILs and the informed use of ILs in drug development and medicine.

Ecotoxicity studies reveal that organic cations in dicamba-derived ionic liquids can pose a greater environmental risk than the herbicide itself

The following research provides novel and relevant insights into potential environmental consequences of combination of various organic cations with commercial systemic herbicide (dicamba), in accordance with a 'herbicidal ionic liquids' (HILs) strategy. Toxicity assays of five dicamba-based HILs comprising different hydrophobic and hydrophilic cations, namely choline [CHOL][DIC], ethyl betainate [BETC2][DIC], decyl betainate [BETC10][DIC], hexadecyl betainate [BETC16][DIC] and didecyldimethylammonium [DDA][DIC]), have been tested towards bacteria (Pseudomonas putida, Escherichia coli, Bacillus subtilis), algae (Chlorella vulgaris), fresh and marine water crustaceans (Daphnia magna, Artemia franciscana). The structure of respective substituents in the cation emerged as a decisive determinant of toxicity in the case of tested species. In consequence, small ions of natural origin ([CHOL] and [BETC2]) demonstrated toxicity numerous orders of magnitude lower compared to fully synthetic [DDA]. These results emphasize the role of cations' hydrophobicity, as well as origin, in the observed acute toxic effect. Time-dependent toxicity assays also indicated that betaine-type cations comprising an ester bond can rapidly transform into less harmful substances, which can generally result in a reduction in toxicity by even several orders of magnitude. Nonetheless, these findings challenge the concept of ionic liquids with herbicidal activity and give apparent parallels to adjuvant-dependent toxicity issues recently noted in typical herbicidal formulations.

Functionalization Methods of Starch and Its Derivatives: From Old Limitations to New Possibilities

It has long been known that starch as a raw material is of strategic importance for meeting primarily the nutritional needs of people around the world. Year by year, the demand not only for traditional but also for functional food based on starch and its derivatives is growing. Problems with the availability of petrochemical raw materials, as well as environmental problems with the recycling of post-production waste, make non-food industries also increasingly interested in this biopolymer. Its supporters will point out countless advantages such as wide availability, renewability, and biodegradability. Opponents, in turn, will argue that they will not balance the problems with its processing and storage and poor functional properties. Hence, the race to find new methods to improve starch properties towards multifunctionality is still ongoing. For these reasons, in the presented review, referring to the structure and physicochemical properties of starch, attempts were made to highlight not only the current limitations in its processing but also new possibilities. Attention was paid to progress in the non-selective and selective functionalization of starch to obtain materials with the greatest application potential in the food (resistant starch, dextrins, and maltodextrins) and/or in the non-food industries (hydrophobic and oxidized starch).

Application of interpretable machine learning models to improve the prediction performance of ionic liquids toxicity

With the wide application prospect of ionic liquids (ILs) as solvent in the future industry, in order to promote green and sustainable chemical engineering, the toxicity problem of common concern has been systematically modeled. Machine learning has promoted the development of chemical property prediction model with its powerful data processing ability. Two typical ensemble learning models, Random Forest (RF) and eXtreme Gradient Boosting (XGBoost), were used to model the toxicity of ILs to Vibrio fischeri in this work. The model's hyperparameters were fine-tuned using Bayesian optimization, and its robustness was enhanced through the 5-fold cross validation. The results of the model comparison showed that the XGBoost model exhibited good generalization ability. In addition, the SHapley Additive exPlanations (SHAP) method was used to explain the model in more detail and the XGBoost model was used to supplement the toxicity value matrix of 1590 ILs.

The effects of the IM1-12Br ionic liquid and the oxytetracycline mixture on selected marine and brackish microorganisms

The number of applications and commercialized processes utilizing ionic liquids has been increasing, and it is anticipated that this trend will persist and even intensify in the future. Ionic liquids possess desirable characteristics, such as low vapor pressure, good water solubility, amphiphilicity, and stability. Nevertheless, these properties can influence their environmental behavior, resulting in resistance to biotic and abiotic degradation and subsequent water contamination with more harmful derivatives. However, there is a notable scarcity of data regarding the impact of mixtures comprising ionic liquids and other micropollutants. Identifying potential potentiation of ionic liquids (Ils) toxicity in the presence of other xenobiotics is a proactive risk assessment measure. Therefore, the study aims to fill an important knowledge gap and identify possible interactions between imidazolium-based ionic liquid (IM1-12Br) and the common antibiotic oxytetracycline (OXTC). During 11-day experiments, selected marine, brackish and freshwater microorganisms (diatom Phaeodactylum tricornutum, cyanobacterium Microcystis aeruginosa and green algae Chlorella vulgaris) were exposed to binary mixtures of target substances. The assessed responses encompassed chlorophyll a kinetic parameters related to photosynthesis efficiency, as well as pigment concentrations, specifically phycobilin content. Additionally, the impact on the luminescent marine bacterium Aliivibrio fischeri has been evaluated. Significant effects on the growth, photosynthetic processes, and pigment content were observed in all the targeted microorganisms. The concentration addition (CA) and independent action (IA) mathematical models followed by the Model Deviation Ratio (MDR) evaluation enabled the identification of mainly synergistic interactions in the studied mixtures. The findings of present study offer valuable insights into the impacts of ionic liquids and other organic micropollutants.

Fenton and photo-assisted advanced oxidative degradation of ionic liquids: a review

Ionic liquids (ILs) are the class of materials which are purely ionic in nature and liquid at room temperature. Their remarkable properties like very low vapour pressure, non-inflammable and high heat resistance are responsible for their use as a very appealing solvent in a variety of industrial applications in place of regular organic solvents. Because ILs are water soluble to a certain extent, the industrial wastewater effluents are found to contaminate with their traces. The non-biodegradability of ILs attracts the attention of the researchers for their removal or degradation from wastewater. Numbers of methods are available for the treatment of wastewater. However, it is very crucial to use the most efficient method for the degradation of ILs. Advanced oxidation process (AOP) is one of the most important techniques for the treatment of ILs in wastewater which have been investigated during last decades. This review paper covers the cost-effective Fenton, photochemical and photocatalytic AOPs and their combination that could be applied for the degradation of ILs from the wastewater. Theoretical explanations of these AOPs along with experimental conditions and kinetics of degradation or removal of ILs from water and wastewater have been reported and compared. Finally, future perspectives of IL degradation are presented.

A comprehensive study demonstrating the influence of the solvent composition on the phytotoxicity of compounds, as exemplified by 2,4-D-based ILs with a choline-type cation

BACKGROUND

Growing concern for the protection of the environment and existing ecosystems has resulted in increasing consideration of phytotoxicity tests as valid ecotoxicological indicators of the potential hazards of the use of ionic liquids (ILs) or any other chemical. The objective of this study was to gain a detailed understanding of the influence of the solvent composition of spray solutions on the phytotoxic effect of foliar application of ionic pairs with weak (choline 2,4-dichlorophenoxyacetate, [Chol][2,4-D]), medium (N-hexylcholine 2,4-dichlorophenoxyacetate, [C6 Chol][2,4-D]) and good (N-dodecylcholine 2,4-dichlorophenoxyacetate, [C12 Chol][2,4-D]) surface-active properties.

RESULTS

Experimental results unambiguously demonstrated that the biological activity of the test salt solutions, particularly [Chol][2,4-D] and [C6 Chol][2,4-D], can be strongly affected by the addition of an organic solvent, such as methanol, ethanol, dimethylformamide (DMF) or dimethylsulfoxide (DMSO) compared to solutions in pure water. However, the observed tendency is less pronounced for the compound exhibiting good surface activity, [C12 Chol][2,4-D].

CONCLUSIONS

The collected findings show that caution is warranted in the exploitation or modification of methodologies for assessing phytotoxicity to ensure the reliable interpretation of obtained results for environmental risk assessment or building quantitative structure-activity relationship (QSAR) models. © 2023 Society of Chemical Industry.

Hormone-mediated multi- and trans-generational reproductive toxicities of 1-ethyl-3-methylimidazolium hexafluorophosphate on Caenorhabditis elegans

Ionic liquids (ILs) are emergent pollutants and their reproductive toxicities show hormesis, earning attentions on their environmental risk. Yet, their reproductive effects over generations and the mechanisms were seldom explored. In the present study, the reproductive effects of 1-ethyl-3-methylimidazolium hexafluorophosphate ([C₂mim]PF₆) on Caenorhabditis elegans were measured in 11 continuously exposed generations (F1 to F11) to explore the multi-generational effects, and also in the non-exposed generations of F1 and F11 (i.e., their great-grand-daughters, T4 and T4') to explore the trans-generational effects. In multi-generational reproductive effects, there were concentration-dependent hormetic effects with hazard-benefit alteration between low and high concentrations (e.g., in F3). There were also generation-dependent hormetic effects with hazard-benefit alterations over generations (e.g., between F4 and F5, between F8 and F9, and between F10 and F11). Meanwhile, the results also showed benefit-hazard alteration between F2 and F3, between F6 and F7, and between F9 and F10. Trans-generational effects showed common inhibitions in T4 and T4' at both low and high concentrations. In the biochemical analysis, hormones and hormone-like substances including progesterone (P), estradiol (E2), prostaglandin (PG) and testosterone (T) showed multi- and trans-generational changes with inhibition and stimulation, which contributed to the reproductive outcomes in each generation. Such contribution was also observed in the hormones' precursor cholesterol and the proteins that are essential for reproduction including vitellogenin (Vn) and major sperm protein (MSP). Moreover, the biochemicals showed significant involvement in the connection among generations. Furthermore, the multi- and trans-generational effects of [C₂mim]PF₆ and histidine showed similar modes of actions despite some differences, implying the contribution of their shared imidazole structure.

Effects of [Cnpy]Br (n=3,5) on the growth and physiology of rape seedlings

1-Alkylpyridinium bromide [C_npy]Br is a common intermediate in chemical synthesis. With the discharge of industrial wastewater, it enters the environment and is toxic to plants. In this study, the impacts of two pyridine-based ionic liquids (ILs), [C₃py]Br and [C₅py]Br, on the growth and physiology of rape seedlings were investigated at concentrations of 10, 50, 100, 200, 300, and 400 mg/L. Within the concentration range (10-400 mg/L) of [C₃py]Br and [C₅py]Br treatment, the root length, plant height, activities of antioxidant enzymes (SOD, POD, and CAT), and the contents of Chla and Chlb showed an increase at low concentrations and a decrease at high concentrations. [C₃py]Br and [C₅py]Br increased MDA content in rape seedlings leaves in a concentration-dependent manner. It was also found that [C₅py]Br was more toxic to rape seedlings than [C₃py]Br. The toxicity of pyridine ILs such as [C₃py]Br and [C₅py]Br to plants should be highly concerned.

Salinity fluctuation influences the toxicity of 1-octyl-3-methylimidazolium chloride ([C8mim]Cl) to a marine diatom Phaeodactylum tricornutum

In this work, a marine diatom (Phaeodactylum tricornutum) was exposed to 1-octyl-3-methylimidazolium chloride ([C₈mim]Cl) for 96 h at three different salinities (25, 35, and 45 ‰) for investigating their interactive effects. Results showed that values of EC₁₀ and EC₅₀ at 96 h of exposure were 0.29, 1.06, 2.01 μg L^-1 and 7.21, 7.71, 7.25 mg L^-1 when the salinities were 25, 35, and 45 ‰, respectively, meaning that salinity fluctuation affected the toxicity of [C₈mim]Cl to this diatom. Changes in chlorophyll a contents and chlorophyll fluorescence parameters suggested that [C₈mim]Cl and salinity fluctuation had a significant interactive effect on the algal photosynthesis. In addition, soluble protein content and activities of antioxidant enzymes in algal cells changed significantly. Increased malondialdehyde contents indicated that the combined stresses could induce excessive production of reactive oxygen species leading to oxidative damage to the algal cells.

Toward revealing the role of the cation in the phytotoxicity of the betaine-based esterquats comprising dicamba herbicide

In this study, two homologous series of esterquats comprising alkyl (from ethyl to octadecyl) betainate cations and bromide as well as dicamba anions were successfully synthesized, starting from a renewable raw material - glycine betaine. Due to the favorable octanol-water partition coefficient and utilization of biodegradable cations of natural origin, synthesized esterquats can be considered promising alternatives to currently applied dicamba-based formulations. In addition, the obtained results allowed us to verify whether the organic cations in quaternary ammonium salts containing herbicidally active anions (such as dicamba) play the role of biologically inactive adjuvants that only enhance the efficiency of the active ingredient or if they simultaneously exhibit a significant degree of phytotoxicity. Analysis of the influence of alkyl betainate esterquats containing nonherbicidal (bromide) anions on seedlings of white mustard revealed that alkyl betainate cations promote the germination of white mustard seeds; however, the subsequent growth of the seedlings was significantly inhibited. Further studies performed on white mustard and cornflower plants in a stage of 4-6 leaves allowed us to conclude that in the case of sensitive plants, the high phytotoxicity can be attributed to the presence of the dicamba anion, whereas for more resistant plants the additional influence of the cation on the phytotoxic effect is visible. Esterquats comprising a dodecyl substituent or longer had high surface active properties. Nonetheless, their contact angle values were not correlated with phytotoxicity data, indicating an additional influence of the cation on this stage of plant development. Interestingly, subsequent dose-response experiments conducted for two selected dicamba-based products confirmed that the greatest phytotoxicity was expressed by compounds containing a decyl substituent.

Effects of pyridinium-based ionic liquids with different alkyl chain lengths on the growth of maize seedlings

The effects of four water-soluble pyridinium-based ionic liquids (ILs) differing in alkyl side chain length, namely, N-ethyl pyridinium bromide ([EPy]Br), N-butyl pyridinium bromide ([BPy]Br), N-hexyl pyridinium bromide ([HPy]Br), and N-octyl pyridinium bromide ([OPy]Br), on the growth of maize seedlings were investigated for the first time. The results revealed that the phytotoxicity of these ILs was significantly correlated with their concentration and alkyl side chain length. The 8-day 50% inhibition values indicated that the toxicity increased as the length of the alkyl chain increased: [EPy]Br < [BPy]Br < [HPy]Br < [OPy]Br. In addition, root growth was found to be more sensitive to ILs than stem growth. In response to exposure to ILs of increasing concentration, we observed different trends in the pigment contents and specific antioxidant enzyme activities in maize seedlings, whereas the contents of malondialdehyde were significantly increased. In addition, RNA sequencing analysis, performed to examine the gene expression profiles of maize leaves under [HPy]Br and [OPy]Br treatments, revealed that a larger number of genes were differentially expressed in response to [OPy]Br treatment. Furthermore, pathway enrichment analysis revealed that both [HPy]Br and [OPy]Br treatments, and particularly the latter, caused a down-regulation of genes involved in photosynthesis and carbohydrate and nitrogen metabolism. Our findings thus indicate that pyridinium-based IL toxicity might be associated with oxidative stress and changes in gene expression profiles.

Application of a phosphonium-based ionic liquid for reactive textile dye removal: Extraction study and toxicological evaluation

Textile dyeing processes are known for their negative environmental impacts due to the production of aqueous effluents containing toxic dyes. Therefore, new wastewater treatment processes need to be developed to treat such effluents, including Liquid-Liquid Extraction (LLE) process using Ionic Liquids (IL). This work aimed to evaluate the application of the hydrophobic IL trihexyltetradecylphosphonium decanoate to extract black, navy, and royal reactive dyes from water and evaluate the toxicological aspects of the resulting water stream. We investigated the effect of selected parameters, such as pH (2-12), temperature (20-50 °C), salt effects, dye concentration (0.5-50 mg/L), and phase volume ratio (900-9000) on the dye extraction. The results showed extraction yields as high as 97% for the three dyes and an extraction capacity of approximately 300 mg/g for black and navy dyes and 400 mg/g for royal. The toxicity tests involved Lactuca sativa, Triticum aestivium L, and Daphnia magna as bioindicators. The difference between the toxicity of the dye solutions before and after extraction was not statistically significant when L. sativa and Triticum aestivum L were used as bioindicators. However, the extracted solution showed increased toxicity towards D. magna due to traces of IL. Overall, the IL has a high extraction capacity for the black, navy, and royal dyes. Nevertheless, further studies on LLE associated with other processes must be carried out to reduce the risk linked to the toxicity of IL transferred to the water.

Ionic Liquids: Environment-Friendly Greener Solvents for Organic Synthesis

Constituted by ions, ionic liquids (ILs) are evolving as greener solvents for many organic syntheses. Due to their high solvent power and low volatility, ionic liquids are serving as an environment-friendly substitute to conventional volatile organic solvents. The present review introduces ionic liquids as an insight into the diverse recent applications of ILs in organic synthesis.

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 liquid-based antimicrobial materials for water treatment, air filtration, food packaging and anticorrosion coatings

Efforts to widen the scope of ionic liquids applications across diverse research areas have flourished in the last two decades with developments in understanding and tailoring their physical, chemical, and biological properties. The promising applications of ionic liquids-based materials as antimicrobial systems is due to their ability and flexibility to be tailored in varying sizes, morphologies, and surface charges. Ionic liquids are also considered as greener materials. Common methods for the preparation of ionic liquid-based materials include crosslinking, loading, grafting, and combination of ionic liquids with other polymeric materials. Recent research focuses on the tuning of the biological properties to design novel ionic liquids-based antimicrobial materials. Here, the properties, synthesis and applications of ionic liquids and ionic liquids-based materials are reviewed with focus on antimicrobial activities applied to water treatment, air filtration, food packaging, and anticorrosion.

Evaluating the hazardous impact of ionic liquids - Challenges and opportunities

Ionic liquids (ILs), being related to the design of new environmentally friendly solvents, are widely considered for applications within the "green chemistry" concept. Due to their unique properties and wide diversity, ILs allow tailoring new separation procedures and producing new materials for advanced applications. However, despite the promising technical performance, environmental concerns highlighted in recent studies focused on the toxicity and biodegradability of ILs and their metabolites have revealed that ILs safety labels are not as benign as previously claimed. This review refers to the fundamentals about the properties and applications of ILs also in the context of their potential environmental effect. Toxicological issues and harmful effects related to the use of ILs are discussed, including the evaluation of their biodegradability and ecological impact on diverse organisms and ecosystems, also with respect to bacteria, fungi, and cell cultures. In addition, this review covers the tools used to assess the toxicity of ILs, including the predictive computational models and the results of studies involving cell membrane models and molecular simulations. Summing up the knowledge available so far, there are still no reliable criteria for unequivocal attribution of toxicity and environmental impact credentials for ILs, which is a challenging research task.

Ionic Liquids-A Review of Their Toxicity to Living Organisms

Ionic liquids (ILs) were initially hailed as a green alternative to traditional solvents because of their almost non-existent vapor pressure as ecological replacement of most common volatile solvents in industrial processes for their damaging effects on the environment. It is common knowledge that they are not as green as desired, and more thought must be put into the biological consequences of their industrial use. Still, compared to the amount of research studying their physicochemical properties and potential applications in different areas, there is a scarcity of scientific papers regarding how these substances interact with different organisms. The intent of this review was to compile the information published in this area since 2015 to allow the reader to better understand how, for example, bacteria, plants, fish, etc., react to the presence of this family of liquids. In general, lipophilicity is one of the main drivers of toxicity and thus the type of cation. The anion tends to play a minor (but not negligible) role, but more research is needed since, owing to the very nature of ILs, except for the most common ones (imidazolium and ammonium-based), many of them are subject to only one or two articles.

New insights on the effects of ionic liquid structural changes at the gene expression level: Molecular mechanisms of toxicity in Daphnia magna

Knowledge on the molecular basis of ionic liquids' (ILs) ecotoxicity is critical for the development of these designer solvents as their structure can be engineered to simultaneously meet functionality performance and environmental safety. The molecular effects of ILs were investigated by using RNA-sequencing following Daphnia magna exposure to imidazolium- and cholinium-based ILs: 1-ethyl-3-methylimidazolium chloride ([C₂mim]Cl), 1-dodecyl-3-methylimidazolium chloride ([C₁₂mim]Cl) and cholinium chloride ([Chol]Cl)-; the selection allowing to compare different families and cation alkyl chains. ILs shared mechanisms of toxicity focusing e.g. cellular membrane and cytoskeleton, oxidative stress, energy production, protein biosynthesis, DNA damage, disease initiation. [C₂mim]Cl and [C₁₂mim]Cl were the least and the most toxic ILs at the transcriptional level, denoting the role of the alkyl chain as a driver of ILs toxicity. Also, it was reinforced that [Chol]Cl is not devoid of environmental hazardous potential regardless of its argued biological compatibility. Unique gene expression signatures could also be identified for each IL, enlightening specific mechanisms of toxicity.

Growth Performance and Antioxidative Response of Chlorella pyrenoidesa, Dunaliella salina, and Anabaena cylindrica to Four Kinds of Ionic Liquids

Ionic liquids are widely used for lipid and pigment extractions from microalgae. It is possible that ionic liquids are discharged into environments. The evaluation of growth performance and antioxidative response of ionic liquids to microalgae is helpful to explore the stress regulation mechanism and investigate possible environmental risk. Ionic liquids induce production of reactive oxygen species (ROS) to microalgae. These oxidative stresses are possible from cations, anions, and salinity. In this study, the growth inhibitions of [BMIM]Br, [BMIM]Cl, [EMIM]Cl, and [EMIM]EtOSO₃ to Anabaena cylindrica, Chlorella pyrenoidesa, and Dunaliella salina were evaluated. It was interesting that Br^- and two kinds of cations, [BMIM] and [EMIM], had significant effects on growth inhibitions of these microalgae. IC50 values of these ionic liquids for A. cylindrica, C. pyrenoidesa, and D. salina were also estimated based on the results of growth inhibitions. It was proved that [EMIM]Cl is relatively harmless to C. pyrenoidesa and D. salina, and [EMIM]EtOSO₃ is relatively or practically harmless to C. pyrenoidesa. [BMIM]Br and [BMIM]Cl are practically harmless to A. cylindrica and C. pyrenoidesa, and relatively harmless to D. salina. More than 0.8 g/L [EMIM]EtOSO₃ led to bleaching of both A. cylindrica and D. salina at 48 h which was shown that the anion, EtOSO₃^-, had higher inhibition to A. cylindrica and D. salina than Cl^-. In addition, high concentration of ionic liquids led to reductions of chlorophyll content in these three kinds of microalgae, increase of ROS levels and malondialdehyde contents for most of the cases. High concentration of ionic liquids also increased the activities of superoxide dismutase in three kinds of microalgae. There were positive correlations between ROS levels or MDA content, and inhibitions ratios of these ionic liquids to microalgae except [EMIM]Cl to A. cylindrica. These antioxidant enzymes were beneficial for reducing the ROS induced by ionic liquids.

The Heck reaction of allylic alcohols catalysed by an N-heterocyclic carbene-Pd(ii) complex and toxicity of the ligand precursor for the marine benthic copepod Amphiascoides atopus

The palladium-catalysed reaction of aryl halides and allylic alcohols is an attractive method for obtaining α,β-unsaturated aldehydes and ketones, which represent key intermediates in organic synthesis. In this context, a 1,2,3-triazol-5-ylidene (aNHC)-based palladium(ii) complex formed in situ has been found to be a selective catalyst for the syntheses of building blocks from the corresponding aryl halides and allylic alcohols, with yields ranging from 50% to 90%. The lack of toxic effects of the ligand precursor (1,2,3-triazolium salt) of the palladium(ii) complex for the harpacticoid copepod Amphiascoides atopus allowed us to contrast the efficiency of the catalytic system with the potential impact of the principal waste chemical in global aquatic ecosystems, which has not been previously addressed.

A 1,2,3-triazol-5-ylidene (aNHC)-based palladium(ii) complex formed in situ has been found to be an efficient catalyst in the formation of C–C bonds.

Mechanisms of action of ionic liquids on living cells: the state of the art

Ionic liquids (ILs) are a relatively new class of organic electrolytes composed of an organic cation and either an organic or inorganic anion, whose melting temperature falls around room-temperature. In the last 20 years, the toxicity of ILs towards cells and micro-organisms has been heavily investigated with the main aim to assess the risks associated with their potential use in (industrial) applications, and to develop strategies to design greener ILs. Toxicity, however, is synonym with affinity, and this has stimulated, in turn, a series of biophysical and chemical-physical investigations as well as few biochemical studies focused on the mechanisms of action (MoAs) of ILs, key step in the development of applications in bio-nanomedicine and bio-nanotechnology. This review has the intent to present an overview of the state of the art of the MoAs of ILs, which have been the focus of a limited number of studies but still sufficient enough to provide a first glimpse on the subject. The overall picture that emerges is quite intriguing and shows that ILs interact with cells in a variety of different mechanisms, including alteration of lipid distribution and cell membrane viscoelasticity, disruption of cell and nuclear membranes, mitochondrial permeabilization and dysfunction, generation of reactive oxygen species, chloroplast damage (in plants), alteration of transmembrane and cytoplasmatic proteins/enzyme functions, alteration of signaling pathways, and DNA fragmentation. Together with our earlier review work on the biophysics and chemical-physics of IL-cell membrane interactions (Biophys. Rev. 9:309, 2017), we hope that the present review, focused instead on the biochemical aspects, will stimulate a series of new investigations and discoveries in the still new and interdisciplinary field of "ILs, biomolecules, and cells."

The reaction of cucumber to the introduction of ionic liquids into the soil

This paper presents the influence of two bromides, tetrabutylammonium and tetrabutylphosphonium, on the growth and development of cucumber seedlings. The tests were performed at two dates, i.e. 10 and 20 days, after the introduction of increasing amounts of ionic liquids (ILs) into the soil. The applied ILs showed phytotoxicity dependent mainly on the concentration of the substance, which is proved by the inhibition of the length of aboveground parts and their roots and the yield of cucumber fresh mass, from which EC50 values were calculated. The phytotoxicity symptoms were the result of oxidative stress, one of the manifestations of which was a decrease in assimilative pigments, linearly correlated with an increase in bromide concentration in the medium. The stress is also proven by the large increase in hydrogen peroxide, malondialdehyde and free proline in cucumber leaves. The reaction of this plant to oxidative stress was an increase in the activity of antioxidative enzymes such as catalase and peroxidase. As a result of statistical analysis, it was proved that all changes of biomarkers of phytotoxicity of examined ILs and oxidative stress indicators in cucumber seedlings depended more on the applied concentration of these salts than on the date of the study.

The effect of polar head group of dodecyl surfactants on the growth of wheat and cucumber

The increasing application of various surfactants nowadays, may lead to the contamination of the natural environment and represent potential threat to terrestrial higher plants. In this article, the effect of 13 surfactants, with dodecyl alkyl chain and various aromatic (imidazolium, pyridinium, thiazolium) and aliphatic (guanidinium, ammonium, thiosemicarbazidium) polar heads, on germination, development and growth of wheat and cucumber was investigated. The study aimed to prove how changes in lipophilicity of surfactants and their various structural modifications (existence of the aliphatic or aromatic polar group, the introduction of oxygen and sulfur) influence toxicity towards investigated plants. The calculated lipophilic parameter (AlogP) is shown to be a useful parameter for predicting potential toxicity of the compound. The strategy of using surfactants with aliphatic polar heads instead of aromatic prove to be a promising strategy in reducing harmful effect, as well as the introduction of polar groups in the structure of cation. From all investigated compounds, surfactants with imidazolium polar head displayed the most harmful effect towards wheat and cucumber. The cucumber seeds were more sensitive to the addition of surfactants comparing to wheat. All obtained experimental results were additionally investigated using computational methods, simulating the transport of surfactants through a lipid bilayer. The influence of cation tendency to fit in lipid bilayer structure was correlated with toxicity. For the first time, it is concluded that cation ability to mimic the structure of bilayer have less harmful effect on plant development.

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.

Toxic effect of three imidazole ionic liquids on two terrestrial plants

To determine the toxic effect of three imidazole ionic liquids (IILs) in terrestrial monocotyledonous and dicotyledonous plants, three IILs (1-butyl-3-methylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole hexafluorophosphate, and butyl-3-methylimidazolium bi-[(trifluoromethyl)sulfonyl]imide) were investigated using rice and capsicum as target toxicity models. In hydroponic experiments, increasing the concentration of the IILs led to a decrease in the seed germination rate, a decrease in the reduced stem and root lengths, and an increase in the inhibition rate of the stem and root lengths; in addition, as the concentration increased, the reducing sugar content of rice and capsicum seedling leaves and roots first increased and then decreased, while permeability of the cell membranes of the stems and roots of the two plants also gradually increased. In terms of the effects on these indices in rice, the ranking of these three IIL anions was [TF2N]- > [PF6]- > [BF4]-; in terms of the effects on capsicum, the sequence was [BF4]- > [TF2N]- > [PF6]-. These findings provide a theoretical reference for the next step in the synthesis and the use of green ionic liquids.

Effects of nanomaterials on metal toxicity: Case study of graphene family on Cd

The risk of heavy metal cadmium (Cd) on aquatic organisms has drawn widespread attentions, but the effects of nanomaterials (e.g. graphene (G)) on Cd toxicity are rarely clarified. It was known that mixture of contaminants may exhibit more severe impact than the individual metal. Here, we conducted a study systematically on the effects of nanomaterials on the toxicity of Cd to Scenedesmus Obliquus (S. obliquus) with or without the presence of graphene family materials (GFMs) derived from G, such as graphene oxide (GO) and amine-modified graphene (GNH). Our results showed that the influence of GFMs on the acute toxicity of Cd to S. obliquus is in the order of GO > G > GNH based on their EC₅₀ of Cd-GFMs. The effects of GFMs on the cytotoxicity and oxidative damage of Cd to S. obliquus are varied with the concentrations of GFMs. The differences between the effects of GFMs on Cd toxicity may attribute to their different surface oxygen-containing functional groups contained in the nanomaterials. The adsorption capacity of nanomaterials on metal ions, their dispersibility in water and their interaction mode with organisms, may dominate main contributions to their effects on Cd toxicity. Our study aids to clarify the interference of nanoparticles on the ecotoxicity of metals, to avoid the misunderstanding of the potential risk of metals in the complicate water environments.

Mixture toxicity and uptake of 1-butyl-3-methylimidazolium bromide and cadmium co-contaminants in water by perennial ryegrass (Lolium perenne L.)

Ionic liquids, a kind of emerging and persistent organic contaminants, always coexist with heavy metals in aquatic and terrestrial environments. However, the feasibility of phytoremediation to remove ionic liquids and heavy metals co-contaminants is still unclear. Thus, in this study, the hydroponic experiment was conducted to investigate the combined effect of 1-butyl-3-methylimidazolium bromide ([C₄mim]⁺Br^-) and cadmium (Cd²⁺) on growth and physiological indictors of perennial ryegrass, together with their uptake and translocation by plants. Results show that the exposure of ryegrass to [C₄mim]⁺ and Cd²⁺ mixture significantly inhibited the biomass growth and affected the photosynthetic pigments contents in leaves. The increases of lipid peroxidation and catalase, peroxidase activity were also observed under the co-exposure experiments. The mixture toxicity of [C₄mim]⁺ and Cd²⁺ to ryegrass growth showed an additive effect predicted by concentration addition and independent action. [C₄mim]⁺ uptake and acropetal translocation by ryegrass were significantly inhibited with dosing Cd²⁺. In contrast, [C₄mim]⁺ had no obvious effect on Cd²⁺ uptake by ryegrass, while enhanced Cd²⁺ translocation from roots to shoots occurred with increasing [C₄mim]⁺ dosages. These results indicate that the co-contamination of ionic liquids and heavy metals would affect their fates during phytoremediation.

An ionic liquid as a green solvent for high potency synthesis of 2D covalent organic frameworks

The PXRD and simulated profiles of PMDA–TAPA (a) and TFP–EB (b).