Avoid the PCB mistakes: A more sustainable future for ionic liquids

Effects of Different Ionic Liquids on Microbial Growth and Microbial Communities' Structure of Soil

Ionic liquids (ILs) are widely used "green solvent" as they have a low vapor pressure and can replace volatile solvents in industry. However, ILs are difficult to biodegrade and are potentially harmful to the environment. This study, herein, investigated the toxicity of three imidazole ILs ([C8MIM]Cl, [C8MIM]Br, and [C8DMIM]Br) towards soil microorganisms. The results showed that the ILs inhibited the growth of soil culturable microorganisms and affected the activity of soil enzyme. In addition, microbial communities' species and abundance in soil were altered. Finally, functional prediction analysis revealed that ILs mainly affected the carbohydrate metabolism and amino acid metabolic processes of the microorganisms. ILs with single methyl substituent had a more pronounced effect than those with double methyl substituents. The study indicates that the use of ILs with double methyl substituents is more environmentally safe, and that the toxicity of ILs should be taken into account in industrial production for the design and production of more environmentally safe types, such as ILs with double methyl substituents.

Subcellular effects of imidazolium-based ionic liquids with varying anions on the marine bivalve Mytilus galloprovincialis

Green Chemistry involves applying a set of principles aimed at minimizing the use of hazardous substances in the design, production, and application of chemical products. In recent decades, Ionic Liquids (ILs) have emerged as more environmentally friendly substitutes for traditional organic solvents. This preference is primarily due to their low vapor pressure, which results in minimal atmospheric pollution and enhanced industrial safety. However, existing literature highlights the toxicity of ILs towards aquatic invertebrates. Consequently, this study points to assess the biochemical effects of a selection of ILs through an in vitro approach. Specifically, digestive gland and gill cellular fractions (S9) of the marine bivalve Mytilus galloprovincialis were exposed to varying concentrations (0.05-2 μM) of three ILs featuring identical cations but different anions. The ILs tested were 1-ethyl-3-methylimidazolium octanoate ([EMIM][Oct]), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), and 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]). The results indicate that [EMIM][Oct] induces higher toxicity in both S9 tissues, highlighting a strong effect of the anion. Overall, antioxidant and biotransformation defenses were significantly altered for all three ILs assessed. While acetylcholinesterase activity was significantly inhibited of about half of control activity, indicating neurotoxic damage as part of the toxicity mode of action of these ILs, neither lipid peroxidation nor alterations to DNA integrity were observed (≥100 %). This study supports the use of in vitro techniques as important tools capable of generating reliable ecotoxicological data, which can be further considered as a screening before in vivo testing and used for in silico modeling.

High-sensitivity liquid chromatography-tandem mass spectrometry quantitative for alkyl imidazolium ionic liquids in human serum: Advancing biomonitoring of human exposure concerns

Alkyl imidazolium ionic liquids (Cn[MIM]), initially heralded as eco-friendly green solvents for diverse industrial applications, have increasingly been recognized fortheir biodegradability challenges and multiple biotoxicity. Despite potential health risks, research into the effects of Cn[MIM] on human health remains scarce, particularly regarding their detection in biological serum samples. This study validated a matrix-matched calibration quantitative method that utilizes solid-phase extraction (SPE) coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The method was used to analyze the presence of 10 ionic liquids (ILs) with varying alkyl carbon chain lengths (C2-C12) across 300 human serum samples. Efficient separation was achieved using optimized SPE conditions and a BEH C18 column with an appropriate mobile phase. Results demonstrated a strong linear relationship (0.05-100 ng/mL; R2 = 0.995-0.999), with detection and quantification limits with detection and quantification limits ranging from 0.001 to 0.107 ng/mL and 0.003-0.355 ng/mL, respectively. Intraday and inter-day precisions were 0.85-6.99 % and 1.50-7.46 %, with recoveries between 82 and 113 %. The validated method detected C6MIM in 19 % of samples and C8MIM in 8.3 % of samples, with concentrations ranging from 0.02 to 111.70 μg/L and 0.09-16.99 μg/L, respectively, suggesting a potential risk of human exposure. This underscores the importance of robust detection methods in monitoring environmental and human health impacts of alkyl imidazolium compounds.

Acclimation Response of Green Microalgae Chlorella Sorokiniana to 2,3',4,4',6-Pentachlorobiphenyl

The effect of the toxicant 2,3',4,4',6-pentachlorobiphenyl (PCB-119) on the growth, chlorophyll content, and PSII activity of C. sorokiniana cells was investigated. A strong negative effect of the toxicant was observed at PCB concentration of 0.05 μg mL-1 , when culture growth ceased, chlorophyll strongly bleached, and cell death occurred. The use of original highly sensitive fluorimeter to measure three types of high-resolution chlorophyll fluorescence kinetics allowed us to detect an initial dramatic decrease in the activity of primary photosynthetic reactions, followed by their almost complete recovery at the end of the incubation period when most cells were dead. The study of the distribution of individual cells in culture in terms of Fv /Fm parameter, which reflects the quantum yield of PSII photochemistry, revealed the existence of 2-3% of cells retaining high Fv /Fm (>0.7) in the presence of the toxicant. The treated cultures were able to resume growth after prolonged incubation in fresh medium. The high sensitivity fluorescence methods used made it possible to identify stress-resistant cells which maintain high photosynthetic activity in the presence of lethal doses of toxic substances; these cells provide recovery of the population after stress.

Co-curing preparation of flame retardant and smoke-suppressive epoxy resin with a novel phosphorus-containing ionic liquid

Phosphorus-containing ionic liquid derivatives have been proven to be effective flame retardants for epoxy resin (EP). Flame retardants can accelerate the curing process and improve flame retardancy and smoke suppression of EP composites, which is challenging. In this paper, a novel phosphorus-containing ionic liquid (TPP-PF₆) was synthesized and used both as a co-curing agent with 4,4'-diaminodiphenylmethane (DDM) and as a highly effective flame retardant for EP. It has been found that TPP-PF₆ was conducive to improve the char formation of EP to inhibit the smoke release at high temperatures. For EP/TPP-PF₆ composites, the flame-retardant performance was enhanced rapidly with the increase of TPP-PF₆. With only 2 wt% of TPP-PF₆, EP/2.0TPP-PF₆ reached a UL-94 V-0 rating and a limiting oxygen index of 30.3%. The peak heat release rate, total heat release, and total smoke production values of EP/2.0TPP-PF₆ were reduced by 36.32%, 45.81%, and 15.1% compared with those of pure EP, respectively. The thermal degradation products and flame retardant mechanism in gas and condensed phases were studied. It was found that TPP-PF₆ had flame retardant effect in the barrier effect of the condensed phase and the quenching effect of the gas phase. This work explores the high-efficiency flame retardant and smoke-suppressive structures with co-curing properties for EP, thus promoting the wide application of EP materials.

Sonoluminescence Spectra in the First Tens of Seconds of Sonolysis of [BEPip][NTf2], at 20 kHz under Ar

Following recent works on the sonochemical degradation of butyl ethyl piperidinium bis-(trifluoromethylsulfonyl)imide ([BEPip][NTf₂]), monitoring of sonoluminescence (SL) spectra in the first tens of seconds of sonolysis was needed to better characterize the formed plasma and to question the correlation of the SL spectra with the viscosity. A very dry [BEPip][NTf₂] ionic liquid (IL) and a water-saturated liquid are studied in this paper. In both cases, IL degradation is observed as soon as SL emission appears. It is confirmed that the initial evolution of the SL intensity is closely linked to the liquid viscosity that impacts the number of bubbles; however, other parameters can also play a role, such as the presence of water. The water-saturated IL shows more intense SL and faster degradation. In addition to the expected bands, new emission bands are detected and attributed to the S₂ B-X emission, which is favored in the water-saturated ionic liquid.

Flexibility is the key to tuning the transport properties of fluorinated imide-based ionic liquids

Ionic liquids are becoming increasingly popular for practical applications such as biomass processing and lithium-ion batteries. However, identifying ionic liquids with optimal properties for specific applications by trial and error is extremely inefficient since there are a vast number of potential candidate ions. Here we combine experimental and computational techniques to determine how the interplay of fluorination, flexibility and mass affects the transport properties of ionic liquids with the popular imide anion. We observe that fluorination and flexibility have a large impact on properties such as viscosity, whereas the influence of mass is negligible. Using targeted modifications, we show that conformational flexibility provides a significant contribution to the success of fluorination as a design element. Contrary to conventional wisdom, fluorination by itself is thus not a guarantor for beneficial properties such as low viscosity.

Sensitive determination of polychlorinated biphenyls from beverages based on switchable solvent microextraction: A robust methodology

Polychlorinated biphenyls (PCBs) are a kind of hazardous persistent organic contaminants and widely present in nature due to large consumption in the past. Although PCBs have been banned in many countries of the world, they are still present at trace level in food and water samples. It is of significant value to establish reliable enrichment and detection method. Based on the conversion of the hydrophilicity and hydrophobicity from heptanoic acid under alkali and acid, increasing the contact area between heptanoic acid and PCBs, a new switchable solvent micro-extraction method for PCBs from beverages was developed with good extraction efficiency using heptanoic acid as the extractant prior to gas chromatography-tandem mass spectrometry (GC-MS/MS). The key parameters that had impact on enrichment of PCBs were investigated in detail. Under the optimal conditions, a good linearity can be achieved in a concentration range of 0.01-20 μg L^-1 with the correlation coefficients of 0.9978-0.9994. Limits of detection for PCB28, PCB53, PCB206 were 3 ng L^-1 and PCB118 was 5 ng L^-1 while other target PCBs were 2 ng L^-1. Intra-day and inter-day precisions were in the range of 1.9-4.2% and 2.1-4.2％(relative standard deviation, RSD, n = 6), respectively. The real sample spiked recoveries of the targets were in the range of 93.2-114.3％ (n = 3). The enrichment factors were in the range of 16.2-17.9. The results proved that this method was reliable for monitoring trace PCBs in beverage samples and will help for future assessments of impacts on human and animal health.

Physiological responses of Pichia stipitis to imidazolium chloride ionic liquids with different carbon chain length

Ionic liquids (ILs) are used as detoxication agents for fermentation of lignin into ethanol because of their good applicability. However, the residual ILs may be toxic to the yeast. In order to improve the use of ILs for fermentation and protected environment, the toxicity of ILs with different carbon chain length to Pichia stipitis was studied in this paper. Four kinds of common imidazolium chloride ILs ([C₄mim]Cl, [C₆mim]Cl, [C₈mim]Cl and [C₁₀mim]Cl) were selected. ILs can inhibit the proliferation of Pichia stipitis and increase their mortality. Oxidative stress reaction occurred in the cells, and the activities of antioxidant enzymes are affected. Comparing with the integrated biomarker response (IBR) index, it was found that the toxicity increases with increasing chain length. ILs may enter cells by damaging cell membranes and reduce ethanol production by damaging organelles such as mitochondria. ILs caused wrinkles and dents on the surface of cells up to cell deformation and even rupture. The toxicity sequence was as follows: [C₁₀mim]Cl> [C₈mim]Cl>[C₆mim]Cl>[C₄mim]Cl. Due to this toxicity to Pichia stipitis, these compounds should be used carefully in the fermentation process and also to avoid toxic effects on other organisms in the environment.

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

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

Filling the knowledge gap: A suspect screening study for 1310 potentially persistent and mobile chemicals with SFC- and HILIC-HRMS in two German river systems

Persistent and mobile chemicals (PM chemicals) were searched for in surface waters by hydrophilic interaction liquid chromatography (HILIC) and supercritical fluid chromatography (SFC), both coupled to high resolution mass spectrometry (HRMS). A suspect screening was performed using a newly compiled list of 1310 potential PM chemicals to the data of 11 surface water samples from two river systems. In total, 64 compounds were identified by this approach. The overlap between HILIC- and SFC-HRMS was limited (31 compounds), confirming the complementarity of the two methods used. The identified PM candidates are characterized by a high polarity (median logD -0.4 at pH 7.5), a low molecular weight (median 187 g/mol), are mostly ionic (54 compounds) and contain a large number of heteroatoms (one per four carbons on average). Among the most frequently detected novel or yet scarcely investigated water contaminants were cyanoguanidine (11/11 samples), adamantan-1-amine (10/11), trifluoromethanesulfonate (9/11), 2-acrylamido-2-methylpropanesulfonate (10/11), and the inorganic anions hexafluorophosphate (11/11) and tetrafluoroborate (10/11). 31% of the identified suspects are mainly used in ionic liquids, a chemically diverse group of industrial chemicals with numerous applications that is so far rarely studied for their occurrence in the environment. Prioritization of the findings of PM candidates is hampered by the apparent lack of toxicity data. Hence, precautionary principles and minimization approaches should be applied for the risk assessment and risk management of these substances. The large share of novel water contaminants among these findings of the suspect screening indicates that the universe of PM chemicals present in the environment has so far only scarcely been explored. Dedicated analytical methods and screening lists appear essential to close the analytical gap for PM compounds.

Cumulative impact assessment of hazardous ionic liquids towards aquatic species using risk assessment methods

In the present research work, a comprehensive tool for cumulative ecotoxicological impact assessment of ionic liquids (ILs) to aquatic life has been constructed. Using the probabilistic tool, impact of individual ILs to a group of aquatic species is assessed by chemical toxicity distributions (CTDs). The impact of group of ILs to individual aquatic species is assessed by species sensitivity distributions (SSDs). Acute toxicity data of imidazolium ILs with chloride (Cl^-), bromide (Br^-), tetrafluoroborate (BF4^-), and hexafluorophosphate (PF6^-) anions are used in CTD and SSD. Allowable concentrations for a group of Imidazolium ILs with the same mode of action (SMOA) to five aquatic species; Daphnia magna, Vibrio fischeri, Algae, Zebrafish, and Escherichia coli are estimated by CTDs. It has been concluded that 1-Butyl-3-methylimidazolium chloride (BMIMCl) possess the lowest risk at an acceptable risk value of 750 × 10^-5 mmol/L which is 12% less than that of OMIMCl. Furthermore, the sensitivities towards the aquatic species reveal that from the studied ILs, BMIMBF4 with an acceptable risk value of 3200 × 10^-5 mmol/L is the most suitable IL towards the selected aquatic species. Hence, current work provides cumulative allowable concentrations and acceptable risk values for ILs which release to aquatic compartment of ecosystem.

The toxicological mechanism of two typical imidazole ionic liquids in textile industry on Isatis tinctoria

Ionic liquids (ILs¹) which are called "green solvents", are used widely in the textile industry as adjuvants due to their many advantages. However, their persistent residues may cause ecotoxicity. The aim of the study is to explore the toxicity of different anions on imidazole ILs and their toxicological mechanism. For the experiments 1-butyl-3-methylimidazole tetrafloroborate ([C₄mim]BF₄) and 1- butyl -3-methylimidazolium chloride ([C₄mim]Cl) were selected to study their toxic effects on Isatis tinctoria. ILs may affect the germination rate. Fresh weight, dry weight and Hill reaction activity decreased continuously with increasing of IL concentrations, showing an effect-dose relationship. Transmission electron microscopy (TEM) revealed that cell walls were fuzzy, starch granules had accumulated and the chloroplast structure was damaged. These changes will affected the function and electron transport efficiency of photosystemⅡ. Superoxide anion accumulation stimulated the activity of antioxidant enzymes (SOD, POD, CAT) and caused lipid peroxidation as well as an increased malondialdehyde content. ILs also reduced indirubin and total flavonoids contents, which reduced the pharmacological efficacy of Isatis tinctoria. This is demonstrated by three-dimensional fluorescence chromatogram. [C₄mim]Cl was more toxic than [C₄mim]BF₄. ILs caused toxic effects to Isatis tinctoria. The ecological toxicity of ILs should be considered when using them as additives in the textile industry.

Targeted modifications in ionic liquids - from understanding to design

Ionic liquids are extremely versatile and continue to find new applications in academia as well as industry. This versatility is rooted in the manifold of possible ion types, ion combinations, and ion variations. However, to fully exploit this versatility, it is imperative to understand how the properties of ionic liquids arise from their constituents. In this work, we discuss targeted modifications as a powerful tool to provide understanding and to enable design. A 'targeted modification' is a deliberate change in the structure of an ionic liquid. This includes chemical changes in an experiment as well as changes to the parameterisation in a computer simulation. In any case, such a change must be purposeful to isolate what is of interest, studying, as far as is possible, only one concept at a time. The concepts can then be used as design elements. However, it is often found that several design elements interact with each other - sometimes synergistically, and other times antagonistically. Targeted modifications are a systematic way of navigating these overlaps. We hope this paper shows that understanding ionic liquids requires experimentalists and theoreticians to join forces and provides a tool to tackle the difficult transition from understanding to design.

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

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

The glutathione S-transferase genes in marine rotifers and copepods: Identification of GSTs and applications for ecotoxicological studies

Various xenobiotics are constantly being released and accumulated into the aquatic environments and consequently, the aquatic organisms are continuously being exposed to exogenous stressors. Among various xenobiotic detoxifying enzymes, Glutathione S-transferase (GST) is one of the major xenobiotic detoxifying enzyme which is widely distributed among living organisms and thus, understanding of the nature of GSTs is crucial. Previous studies have shown GST activity in response to various xenobiotics yet, full identification of GSTs in marine invertebrates is still limited. This review covers information on the importance of GSTs as a biomarker for emerging chemicals and their response to wide ranges of environmental pollutants as well as in-depth phylogenetic analysis of marine invertebrates, including recently identified GSTs belonging to rotifers (Brachionus spp.) and copepods (Tigriopus japonicus and Paracyclopina nana), with unique class-specific features of GSTs, as well as a new suggestion of GST evolutionary pathway.

A biphasic system based on guanidinium ionic liquid: Preparative separation of eicosapentaenoic acid ethyl ester and docosahexaenoic acid ethyl ester by countercurrent chromatography

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are high nutritional components. Evidence for unique effects of them is increasing. Further understanding of their independent biological functions urgently needs more efficient separation techniques. Nowadays, most of the commercially available fish oil products are the mixture of eicosapentaenoic acid ethyl ester (EPAEE) and docosahexaenoic acid ethyl ester (DHAEE). It will be convenient to directly separate esterified EPA and DHA without saponification pretreatment. However, it is of great challenge to separate EPAEE and DHAEE because of their extremely fat-soluble nature and the equivalent chain length rule. In this research, the suitability of green guanidinium ionic liquid (IL) in countercurrent chromatography (CCC) solvent system for the separation of them was evaluated for the first time. Compared with imidazolium IL and phosphonium IL, guanidinium IL based non-aqueous biphasic system showed more outstanding separation performance. The separation mechanism was elucidated in depth through quantum mechanical calculations. It was found that guanidinium IL acted a crucial role in the CCC separation, which resulted in difference of partition behavior of EPAEE and DHAEE via different hydrogen-bonding affinity. EPAEE and DHAEE were successfully separated by solvent system (n-heptane/methanol/propylguanidinium chloride ([C₃Gun]Cl, 1:1:5%, v/v/m)) with high purity (>95%) in one step, which was not achieved beforehand. Moreover, an easy recycling procedure of IL had also been devised, which significantly reduced waste generated. It opens up a new way for reasonable design water-free two-phase solvent system for efficient separation of very non-polar lipid compounds.

Sustainable Battery Materials from Biomass

Sustainable sources of energy have been identified as a possible way out of today's oil dependency and are being rapidly developed. In contrast, storage of energy to a large extent still relies on heavy metals in batteries. Especially when built from biomass-derived organics, organic batteries are promising alternatives and pave the way towards truly sustainable energy storage. First described in 2008, research on biomass-derived electrodes has been taken up by a multitude of researchers worldwide. Nowadays, in principle, electrodes in batteries could be composed of all kinds of carbonized and noncarbonized biomass: On one hand, all kinds of (waste) biomass may be carbonized and used in anodes of lithium- or sodium-ion batteries, cathodes in metal-sulfur or metal-oxygen batteries, or as conductive additives. On the other hand, a plethora of biomolecules, such as quinones, flavins, or carboxylates, contain redox-active groups that can be used as redox-active components in electrodes with very little chemical modification. Biomass-based binders can replace toxic halogenated commercial binders to enable a truly sustainable future of energy storage devices. Besides the electrodes, electrolytes and separators may also be synthesized from biomass. In this Review, recent research progress in this rapidly emerging field is summarized with a focus on potentially fully biowaste-derived batteries.

Ion chromatography for monitoring [NTf2]- anion contaminants in pure and saline water

Hydrophobic ionic liquids containing bis(trifluoromethanesulfonyl)imide, [NTf2]-, anions partially dissolve in aqueous phases. The potential ecotoxicity of [NTf2]- means wastewater streams must be closely monitored to avoid environmental release. A new ion chromatography method is presented, which improves on existing techniques and methods by significantly decreasing analysis time and improving chromatographic peak properties. Consequently, the limit of detection is lowered to 5 μM (1.4 ppm) and limit of quantification lowered to 30 μM (8.5 ppm). The method is reproducible and has a high precision for short and medium chain length ionic liquids (RSD = 0.95%); however, microemulsion effects increase measurement errors for long chain ionic liquids (RSD = 2.32%), albeit by a relatively small amount. Hence, the method is a highly accurate analytical method for highly polarizable [NTf2]- anions, and quantification in the presence of high salinity samples, such as seawater, is readily achieved. Importantly, this method is a significant improvement on existing techniques (chromatography, NMR, UV-Vis) for many reasons, making it ideal for environmental monitoring or process design of [NTf2]- ionic liquid-based applications.

Oxidative stress response and proteomic analysis reveal the mechanisms of toxicity of imidazolium-based ionic liquids against Arabidopsis thaliana

Ionic liquids (ILs) are extensively used in various fields, posing a potential threat in the ecosystem because of their high stability, excellent solubility, and biological toxicity. In this study, the toxicity mechanism of three ILs, 1-octyl-3-methylimidazolium chloride ([C₈MIM]Cl), 1-decyl-3-methylimidazolium chloride ([C₁₀MIM]Cl), and 1-dodecyl-3-methylimidazolium chloride ([C₁₂MIM]Cl) on Arabidopsis thaliana were revealed. Reactive oxygen species (ROS) level increased with higher concentration and longer carbon chain length of ILs, which led to the increase of malondialdehyde (MDA) content and antioxidase activity, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and peroxidase (POD) activities. SOD, CAT, and GPX activities decreased in high ILs concentration due to the excessive ROS. Differentially expressed protein was analyzed based on Gene ontology (GO) and KEGG pathways analysis. 70, 45, 84 up-regulated proteins, and 72, 104, 79 down-regulated proteins were identified in [C₈MIM]Cl, [C₁₀MIM]Cl, and [C₁₂MIM]Cl treatment, respectively (fold change ≥ 1.5 with ≥95% confidence). Cellular aldehyde metabolic process, mitochondrial and mitochondrial respiratory chains, glutathione transferase and oxidoreductase activity were enriched as up-regulated proteins as the defense mechanism of A. thaliana to resist external stresses. Chloroplast, photosynthetic membrane and thylakoid, structural constituent of ribosome, and transmembrane transport were enriched as the down-regulated protein. Compared with the control, 8 and 14 KEGG pathways were identified forup-regulated and down-regulated proteins, respectively, in three IL treatments. Metabolic pathways, carbon metabolism, biosynthesis of amino acids, porphyrin and chlorophyll metabolism were significantly down-regulated. The GO terms annotation demonstrated the oxidative stress response and effects on photosynthesis of A. thaliana in ILs treatment from biological process, cellular component, and molecular function categories.

A study into the species sensitivity of green algae towards imidazolium-based ionic liquids using flow cytometry

The sensitivity of individual organisms towards toxic agents is an important indicator of environmental pollution. However, organism-specific quantification of sensitivity towards pollutants remains a challenge. In this study, we determined the sensitivity of Chlorella vulgaris (C. vulgaris) and Scenedesmus quadricauda (S. quadricauda) towards three ionic liquids (ILs), 1-alkyl-3-methyl-imidazolium chlorides [C_nmim][Cl] (n = 4,6,8). We kept all external parameters constant to identify the biotic parameters responsible for discrepancies in species sensitivity, and used flow cytometry to determine four conventional endpoints to characterise cell viability and cell vitality. Our results demonstrate that after exposure to the ILs, cell proliferation was inhibited in both species. At the same time, the cell size, complexity and membrane permeability of both algae also increased. However, while Chl a synthesis by S. quadricauda was inhibited, that of C. vulgaris was enhanced. S. quadricauda has evolved a metabolic defense that can counteract the decreased esterase activity that has been shown to occur in the presence of ILs. While it is likely that S. quadricauda was less sensitive than C. vulgaris to the ILs because of this metabolic defense, this alga may also exhibit better membrane resistance towards ILs.

Cation and anion effect on the biodegradability and toxicity of imidazolium- and choline-based ionic liquids

This work studies the effect of the cation and anion on the biodegradability and inhibition of imidazolium- and choline-based ionic liquids (ILs) using activated sludge. Six commercial ILs, formed by combination of 1-Butyl-3-methylimidazolium (Bmim⁺) and N,N,N-trimethylethanolammonium (Choline⁺) cations and chloride (Cl^-), acetate (Ac^-) and bis(trifluoromethanesulfonyl)imide (NTf₂^-) anions were evaluated, all representative counter-ions with markedly different toxicity and biodegradability. Inherent and fast biodegradability tests were used to evaluate both the microorganism inhibition and the IL biodegradability. In addition, the ecotoxicological response (EC₅₀) of the ILs was studied using activated sludge and Vibrio fischeri (Microtox® test). Bmim⁺ and NTf₂^- can be considered as non-biodegradable, whereas aerobic microorganisms easily degraded Choline⁺ and Ac^-. The biodegradation pattern of each cation/anion is nearly unaffected by counter-ion nature. Moreover, concentrations of CholineNTf₂ higher than 50 mg/L caused a partial inhibition on microbial activity, in good concordance with its low EC₅₀ (54 mg/L) measured by respiration inhibition test, which alerts on the negative environmental impact of NTf₂-containing ILs on the performance of sewage treatment plants.

In vitro toxicity assessment and enhanced drug solubility profile of green deep eutectic solvent derivatives (DESDs) combined with theoretical validation

Green solvents are actively taking over as the absolute replacement of intrinsic toxic volatile organic solvents. This is conspicuously analyzed in this study, which mentions the preparation of green deep eutectic solvent derivatives (DESDs) composed of choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and two acids, viz., oxalic acid (OX) and citric acid (CA) as preliminary hydrogen bond donors (HBDs) with ethylene glycol (EG) and glycerol (GLY) as secondary HBDs in an equimolar ratio. This study exposes the vigilant choice of the type and mole ratio of HBA and HBDs, which permit the extended stability of the formulated DESDs in the liquid state even below the room temperature. The prepared DESDs were well-characterized by FT-IR spectroscopy. Furthermore, this work aimed at investigating their antimicrobial activity towards selected bacterial and fungal strains expressed in terms of viscosity measurements. The in vitro toxicity profiles in terms of cytotoxicity (human cervical cancer cell line) and genotoxicity (DNA fragmentation), which have not been reported to date, were also assessed for the prepared DESDs. Tuning the HBA and HBDs in selected DESDs for promising biological activity was found to have ethical implications. In addition, this study focused on the solubilization enhancement of the local anaesthetic drug lidocaine (LDC) in the stated DESDs as a function of water composition, and higher solubility was observed due to the fair intermolecular hydrogen bonding interactions between LDC and DESDs, which was further validated using the computational simulation approach. In addition, the electron-donating and accepting sites were depicted by 3D-molecular electrostatic potential (3D-MEP) for the examined systems. The observed variations were attributed to the changes in the solvation capacity, viscosity and ionic strength of pure DESDs as a function of water concentration. Finally, this study supports the role of dual HBDs in leading to the formation of stable DESDs with noteworthy action towards drug solubilization and a remarkable biological response.

Scheme illustrating the sustainable preparation of deep eutectic solvent derivatives (DESDs), their biological response and water-insoluble hydrophobic drug dissolution trend.

Photochemical formation of hydroxylated polychlorinated biphenyls (OH-PCBs) from decachlorobiphenyl (PCB-209) on solids/air interface

In this work, the photochemical transformation of decachlorobiphenyl (PCB-209) on the surface of several solid particles were systematically evaluated under simulated solar irradiation. The degradation kinetics of PCB-209 were first investigated using silica as a model aerosol particulate. It was found that PCB-209 photodegradation was enhanced at small silica particle size, low surface coverage and low humidity. Electron paramagnetic resonance (EPR) analysis and radicals quenching experiments demonstrated that hydroxyl radicals contributed to PCB-209 degradation. Stepwise hydrodechlorination, hydroxyl addition and cleavage of the CC bridge bond were mainly observed in the reaction process, leading to the formation of lower chlorinated PCBs, hydroxylated PCBs (OH-PCBs) and chlorophenols. Based on density functional theory (DFT) calculation, the dissociation energy of the CCl bond requires 354.81-359.79 kJ/mol energy that corresponds to a wavelength of less than 322 nm. And the minimum activation energy of OH radicals attack on PCB-209 is only 18.12 kJ/mol. Photochemical transformation of PCB-209 can also occur on the surface of natural particles, but the rates were inhibited as compared to silica. The hydroxylation and hydrodechlorination products of PCB-209 were detected in all natural particles. This study would make significant contribution to understanding the fate of PCBs in solids/air interface.

Physiological responses of Chlorella pyrenoidosa to 1-hexyl-3-methyl chloride ionic liquids with different cations

Ionic liquids (ILs) are massively used in multiple fields of industry, and consequently, they have entered the environment and become potential threats to the respective ecosystems. In this paper, the toxicity of two different cationic types of ILs (1-hexyl-3-methyl pyridine chloride ([C₆Py]Cl) and 1-hexyl-3-methyl imidazole chloride ([C₆MIM]Cl)) to Chlorella pyrenoidosa (C. pyrenoidosa) was investigated. Growth inhibition increased with increasing ILs concentrations. C. pyrenoidosa showed a certain recovery at low ILs concentrations, the growth inhibition decreased from 6.13% to 1.57% of the control from 24 h to 96 h, respectively, in 0.5 mg/L [C₆MIM]Cl treatment. However, growth inhibition was negatively related with exposure time at high concentrations, and the strongest toxic effects were observed after 48 h. The IC₅₀ values (half inhibitory concentration) were 8.47, 6.65, 6.91 and 7.11 mg/L of [C₆MIM]Cl, respectively, in 24, 48, 72, and 96 h, and were 9.05, 6.83, 7.79 and 8.14 mg/L of [C₆Py]Cl, respectively. Chlorophyll content declined with higher concentrations of the ILs. The values of chlorophyll fluorescence parameters: the maximum effective quantum yield of photosystem II (PSII) (F_v/F_m), maximum quantum yield in PSII (F_v/F₀), and photosynthetic efficiency in PSII (Y(II)), decreased, whereas the minimal fluorescence (F₀) increased following the ILs treatment, indicating damage to the photosystem II. [C₆MIM]Cl and [C₆Py]Cl caused deformation of algae cells, plasmolysis, and damage of the cell membrane and cell wall, and affected organelle structure. Reactive oxygen species (ROS) concentrations increased with higher ILs concentrations from, and superoxide dismutase and catalase activity first increased and then decreased, indicating that the antioxidant defense system was activated to counteract ROS. ROS was the main stress in C. pyrenoidosa induced by ILs, and compared with [C₆Py]Cl, [C₆MIM]Cl were more toxic to C. pyrenoidosa.

Effect of differently methyl-substituted ionic liquids on Scenedesmus obliquus growth, photosynthesis, respiration, and ultrastructure

Concerns have been raised regarding the ecotoxicity of ionic liquids (ILs) owing to their wide usage in numerous fields. Three imidazolium chloride ILs with different numbers of methyl substituents, 1-decyl-imidazolium chloride ([C₁₀IM]Cl), 1-decyl-3-methylimidazolium chloride ([C₁₀MIM]Cl), and 1-decyl-2,3-dimethylimidazolium chloride ([C₁₀DMIM]Cl), were examined to assess their effects on growth, photosynthesis pigments content, chlorophyll fluorescence, photosynthetic and respiration rate, and cellular ultrastructure of Scenedesmus obliquus. The results showed that algal growth was significantly inhibited by ILs treatments. The observed IC_50,48h doses were 0.10 mg/L [C₁₀IM]Cl, 0.01 mg/L [C₁₀MIM]Cl, and 0.02 mg/L [C₁₀DMIM]Cl. The chlorophyll a, chlorophyll b, and total chlorophyll content declined, and the chlorophyll fluorescence parameters, minimal fluorescence yield (F₀), maximal fluorescence yield (F_m), maximum quantum yield of PSII photochemistry (F_v/F_m), effective quantum yield of PSII [Y(II)], non-photochemical quenching (NPQ) and non-photosynthetic losses yield [Y(NO)] were notably affected by ILs in a dose-dependent manner. ILs affected the primary photosynthetic reaction, impaired heat dissipation capability, and diminished photosynthetic efficiency, indicating negative effects on photosystem II. The photosynthetic and respiration rates of algal cells were also reduced due to the ILs treatments. The adverse effects of ILs on plasmolysis and chloroplast deformation were examined using ultrastructural analyses; chloroplast swelling and lamellar structure almost disappeared after the [C₁₀MIM]Cl treatment, and an increased number of starch grains and vacuoles was observed after all ILs treatments. The results indicated that one-methyl-substituted ILs were more toxic than non-methyl-substituted ILs, which were also more toxic than di-methyl-substituted ILs. The toxicity of the examined ILs showed the following order: [C₁₀IM]Cl < [C₁₀DMIM]Cl ≤ [C₁₀MIM]Cl.

Growth inhibition and oxidative stress caused by four ionic liquids in Scenedesmus obliquus: Role of cations and anions

Ionic liquids (ILs) are widely used in various industrial applications. However, they are considered potential toxins in aquatic environments because of their physical stability and solubility. The growth inhibition and oxidative stress induced by four ionic liquids with different cations and anions on the green algae Scenedesmus obliquus was investigated in this study. The order of growth inhibition was 1‑hexyl‑3‑methylimidazolium nitrate ([HMIM]NO₃) > 1‑hexyl‑3‑methylimidazolium chloride ([HMIM]Cl) > N‑hexyl‑3‑metylpyridinium bromide ([HMPy]Br) > N‑hexyl‑3‑metylpyridinium chloride ([HMPy]Cl). Imidazolium IL had a higher growth inhibition effect than pyridinium IL, nitrate IL and bromide IL had a higher effect than chloride IL. Reactive oxygen species (ROS) level in S. obliquus increased with increasing IL concentrations. Green fluorescence in [HMIM]Cl treated algae showed increased brightness compared to the [HMPy]Cl treatment, and [HMIM]NO₃ treatment produced increased brightness compared to the [HMPy]Br treatment, suggesting that higher ROS levels were induced by [HMIM]Cl and [HMIM]NO₃. Soluble protein, catalase (CAT), and superoxide dismutase (SOD) activities were stimulated at lower concentrations but were inhibited at higher concentrations. Regression analysis suggested that ROS level is the main index responsible for oxidative stress induced by the four ILs. The ILs induced oxidative damage on S. obliquus, and ROS in high concentration treatments could not be effectively removed by the antioxidant system, leading to oxidative damage and ultimately resulting in growth inhibition and cell death.

Insights into the levulinate-based ionic liquid class: synthesis, cellulose dissolution evaluation and ecotoxicity assessment

New levulinate ionic liquids (ILs) were able to dissolve cellulose in high amounts. The ecotoxicity profiles of these new ILs were also assessed.

Chronic exposure to the ionic liquid [C8mim]Br induces inflammation in silver carp spleen: Involvement of oxidative stress-mediated p38MAPK/NF-κB signalling and microRNAs

The present study aimed to determine the chronic toxicity of 1-methyl-3-octylimidazolium bromide ([C₈mim]Br) on the silver carp to further reveal the toxicological mechanisms of ionic liquids. Chronic exposure of silver carp to [C₈mim]Br at concentrations of 1.095 and 4.380 mg/L for 60 d was conducted under laboratory conditions. The results revealed that chronic exposure to [C₈mim]Br inhibited the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and reduced glutathione (GSH) levels while markedly increasing malondialdehyde (MDA) and protein carbonyl (PC) levels in fish spleen, indicating that [C₈mim]Br treatment induced oxidative stress. Additionally, long-term exposure to [C₈mim]Br markedly upregulated the expressions of nuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), IL-6, tumour necrosis factor-α (TNF-α), and interferon-γ (IFN-γ); altered the levels of transforming growth factor-β (TGF-β); and increased the mRNA levels of p38MAPK, c-fos, c-jun, and c-myc, suggesting that long-term exposure to [C₈mim]Br might promote the inflammatory response in fish spleen and that p38MAPK/NF-κB signalling may potentially be involved in this process. Moreover, [C₈mim]Br-exposure altered lysozyme activity and complement 3 (C3) and immunoglobulin M (IgM) content, indicating that chronic [C₈mim]Br exposure also has immunotoxic effects on silver carp. Furthermore, we also found that [C₈mim]Br exposure reduced miR-125b levels, altered miR-143 levels, and upregulated miR-155 and miR-21 levels, suggesting that these miRNAs may be involved in the [C₈mim]Br-induced inflammatory response in fish spleen. In summary, the present study indicates that chronic exposure to [C₈mim]Br induces inflammation in fish spleen and that oxidative stress-mediated p38MAPK/NF-κB signalling and miRNAs may play a key role in this process.

Kinetics of imidazolium-based ionic liquids degradation in aqueous solution by Fenton oxidation

In the last few years, several works dealing with Fenton oxidation of ionic liquids (ILs) have proved the capability of this technology for their degradation, achieving complete ILs removal and non-toxic effluents. Nevertheless, very little is known about the kinetics of this process, crucial for its potential application. In this work, the effect of several operating conditions, including reaction temperature (50-90 °C), catalyst load (10-50 mg L^-1 Fe³⁺), initial IL concentration (100-2000 mg L^-1), and hydrogen peroxide dose (10-200% of the stoichiometric amount for the complete IL mineralization) on 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) oxidation has been investigated. Under the optimum operating conditions (T = 90 °C; [Fe³⁺]₀ = 50 mg L^-1; [H₂O₂]₀ = 100% of the stoichiometric amount), the complete removal of [C₄mim]Cl (1000 mg L^-1) was achieved at 1.5-min reaction time. From the experimental results, a potential kinetic model capable to describe the removal of imidazolium-based ILs by Fenton oxidation has been developed. By fitting the proposed model to the experimental data, the orders of the reaction with respect to IL initial concentration, Fe³⁺ amount and H₂O₂ dose were found to be close to 1, with an apparent activation energy of 43.3 kJ mol^-1. The model resulted in a reasonable fit within the wide range of operating conditions tested in this work.

A theoretical study on lidocaine solubility in deep eutectic solvents

The solvation of lidocaine in two selected deep eutectic solvents is studied using density functional theory and molecular dynamics methods. The intermolecular forces between lidocaine and the involved molecules are analysed in terms of van der Waals and hydrogen bond interactions. The structure, composition and properties of the lidocaine solvation shells are analysed together with the possible lidocaine clustering. The changes in the solvent structures upon lidocaine solution are also studied. The reported results show that the effective solvation of lidocaine in deep eutectics is because of strong solute-solvent intermolecular interactions accompanied by a slight volume expansion and minor solvent structural changes, thus confirming deep eutectics as suitable media for developing pharmaceutical applications.

Effect of imidazolium-based ionic liquids with varying carbon chain lengths on Arabidopsis thaliana: Response of growth and photosynthetic fluorescence parameters

As green and novel solvents, ionic liquids (ILs) are popular in many industries, which may threaten ecosystems. The effects of three imidazolium-based ILs with different alkyl chain lengths, including 1-octyl-3-methylimidazolium chloride ([C₈mim]Cl), 1-decyl-3-methylimidazolium chloride ([C₁₀mim]Cl), and 1-dodecyl-3-methylimidazolium chloride ([C₁₂mim]Cl) on growth and photosystem of Arabidopsis thaliana were investigated. Root length, fresh weight, cell membrane permeability, and chlorophyll content of whole plant were significantly affected by ILs. Vein clearing, leaf chlorosis, and browning on the A. thaliana leaf abaxial surface occurred, with a dose-response relationship. The effect of ILs on whole plant increased with alkyl chain lengths. Chlorophyll fluorescence parameters of photosynthetic system II (PSII) were all affected in [C₈mim]Cl and [C₁₀mim]Cl treatments, electron-transfer was blocked, and photochemical energy conversion was damaged. There were no significant changes in chlorophyll fluorescence of newly-growing leaves in [C₁₂mim]Cl treatment, but has severe effect on aged leaves. The number and size of starch granules and osmiophilic globules increased, plasmolysis and the chloroplast swelling occurred in [C₈mim]Cl, [C₁₀mim]Cl treatments and on aged leaves in [C₁₂mim]Cl treatment, but no significant damages occurred on newly-growing leaves of [C₁₂mim]Cl treatment, perhaps due to plant self-protection of plant. The results indicating the appropriate use of ILs is needed.

Enantioselectivity of 2,2',3,5',6-Pentachlorobiphenyl (PCB 95) Atropisomers toward Ryanodine Receptors (RyRs) and Their Influences on Hippocampal Neuronal Networks

Nineteen ortho-substituted PCBs are chiral and found enantioselectively enriched in ecosystems. Their differential actions on biological targets are not understood. PCB 95 (2,2',3,5',6-pentachlorobiphenyl), a chiral PCB of current environmental relevance, is among the most potent toward modifying ryanodine receptors (RyR) function and Ca²⁺ signaling. PCB 95 enantiomers are separated and assigned aR- and aS-PCB 95 using three chiral-column HPLC and circular dichroism spectroscopy. Studies of RyR1-enriched microsomes show aR-PCB 95 with >4× greater potency (EC₅₀ = 0.20 ± 0.05 μM), ∼ 1.3× higher efficacy (B_max = 3.74 ± 0.07 μM) in [³H]Ryanodine-binding and >3× greater rates (R = 7.72 ± 0.31 nmol/sec/mg) of Ca²⁺ efflux compared with aS-PCB 95, whereas racemate has intermediate activity. aR-PCB 95 has modest selectivity for RyR2, and lower potency than racemate toward the RyR isoform mixture in brain membranes. Chronic exposure of hippocampal neuronal networks to nanomolar PCB 95 during a critical developmental period shows divergent influences on synchronous Ca²⁺ oscillation (SCO): rac-PCB 95 increasing and aR-PCB 95 decreasing SCO frequency at 50 nM, although the latter's effects are nonmonotonic at higher concentration. aS-PCB95 shows the greatest influence on inhibiting responses to 20 Hz electrical pulse trains. Considering persistence of PCB 95 in the environment, stereoselectivity toward RyRs and developing neuronal networks may clarify health risks associated with enantioisomeric enrichment of PCBs.