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The embryonic and postembryonic developmental toxicity of imidazolium-based ionic liquids (ILs) to the snail Physa acuta was evaluated in this study. The results of embryonic toxicity tests showed that lower concentrations of 1-octyl-3-methylimidazolium bromide ([C8 mim]Br) (1.5 and 2.1 mg/L) inhibited the hatching rate of snail embryos, and partial snails hatched normally and died, while all of the treated embryos died when the exposure concentration was higher than 4.16 mg/L, at which IL caused the deformation, death, and decay of snail embryos. Statistical analyses revealed obvious differences in the hatching rates between three developmental stages in the 2.1 and 2.94 mg/L groups, indicating that the veliger stage is more sensitive to [C8 mim]Br exposure than the blastula and gastrula stages. Furthermore, the 96 h LC50 values of [C8 mim]Br on the tested snails at three developmental stages (juvenile, subadult, and adult) were 70.83 ± 2.99, 97.59 ± 4.05, and 109.3 ± 2.22 mg/L, respectively, indicating that young snails were more sensitive to [C8 mim]Br toxicity than adults. In addition, the 96 h LC50 values of ILs with different alkyl chain lengths, that is, [C12 mim], [C10 mim], [C8 mim], and [C6 mim], in adult snails were 1.35 ± 0.24, 8.96 ± 5.66, 109.3 ± 4, and 359.6 ± 11.6 mg/L, respectively, suggesting that longer alkyl chains can increase the toxicity of imidazolium ILs on snails., (Copyright © 2012 Wiley Periodicals, Inc.)

In the present study, goldfish toxicity and superficial damage from 1-methyl-3-octylimidazolium bromide ([C8 mim]Br) exposure were evaluated by an acute toxicity test. These results show that the 24-h 50% lethal concentration for [C8 mim]Br in goldfish is 244 mg L(-1) , and this indicates that [C8 mim]Br is a chemical with moderate or low toxicity to organisms. Scanning electronic microscope and histological observations revealed that acute exposure to [C8 mim]Br induced obvious superficial damage to the skin, gill filaments, and intestinal villi of the goldfish, and this suggests that the skin, gills, and intestines may be the first direct targets of the ionic liquid in this fish. Histological examination also indicated that [C8 mim]Br-exposure caused damage to the goldfish's hepatopancreas and kidney, consisting mainly of hepatic cords in a loose connection, hepatic cytoplasmic vacuolation, renal parenchyma vacuolization, and intumescence of the renal tubule. In addition, we found that [C8 mim]Br caused a significant increase in malondialdehyde (MDA) level in the hepatopancreases from these goldfish, and thus we suggest that the MDA level may be a biomarker of [C8 mim]Br-toxicity in goldfish., (Copyright © 2011 Wiley Periodicals, Inc.)

The cytotoxicity of alkylmethylimidazolium-based ionic liquids on rat pheochromocytoma (PC12) cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, lactate dehydrogenase release (LDH), and acridine orange staining in the present study. Mitochondrial depolarization, DNA fragmentation, reactive oxygen species (ROS) levels, and caspase-3 activity were also determined. The results showed dose-dependent cytotoxicity of ionic liquids on PC12 cells, and the ionic liquids with longer lateral chains had stronger cytotoxicity. Additionally, we found that exposure to the ionic liquid 1-octyl-3-methylimidazolium bromide ([C(8)mim]Br) provoked cellular LDH release, increased mitochondrial depolarization, induced cellular transmogrification, nuclear shrinkage and DNA fragmentation, and promoted caspase-3 activity and ROS levels in PC12 cells. These results suggest that [C(8)mim]Br may induce PC12 cell apoptosis triggered by excessive ROS and mediated by mitochondrial depolarization and permeability transition. Our result may be helpful for illuminating the cytotoxicity mechanism of alkylmethylimidazolium-based ionic liquids and safely using them in the future., (Copyright © 2012 Elsevier Inc. All rights reserved.)

In the present study, the acute toxicity of 1-Alkyl-3-methylimidazolium bromide ([Cnmim]Br) on the green algal Scenedesmus obliquus and Chlorella ellipsoidea was determined. The length of alkyl side chain of these imidazolium ionic liquids were C4, C6, C8, C10 and C12. The primary production of S. obliquus was also assessed after they were exposed to 0.01, 0.05, 0.10, 0.50 and 1.00 mg/L of [C10mim]Br for 96 h. The results showed that the acute toxicity of these ionic liquids was positively correlated with the alkyl chain length. Meanwhile, the concentration of the ionic liquid strongly influenced the primary production of algae. These results indicate that [Cnmim]Br with longer alkyl length have toxic effects on the green algae, and the risk to aquatic ecosystems by ionic liquid's leaking into the water body must be evaluated in the future., (Copyright (c) 2009 Elsevier Inc. All rights reserved.)

To evaluate the toxicity of the ionic liquid 1-methyl-3-octylimidazolium bromide ([C(8)mim]Br) to Eisenia foetida, effects of [C(8)mim]Br on the growth, reproductive ability, and adenosine triphosphatase (ATPase) activity of earthworms were determined under laboratory conditions using artificial soil as substrate. The results showed that [C(8)mim]Br in high concentrations significantly inhibited the growth of the earthworms. These effects were enhanced with prolonged exposure to and increasing concentration of [C(8)mim]Br. E. foetida's reproductive ability was significantly inhibited after 42d of subchronic exposure to [C(8)mim]Br at a concentration >or=5 mg kg(-1) artificial soil (dry weight). During acute exposure, a high concentration of [C(8)mim]Br >or=40 mg kg(-1) artificial soil (dry weight) inhibited the activities of Na(+)-K(+)-ATPase and Mg(++)-ATPase after 3 and 7d of exposure. After 42d of subchronic exposure, the activity of both ATPases was inhibited in groups exposed to >or=5mg[C(8)mim]Brkg(-1) artificial soil (dry weight). These results indicate that treatment with the ionic liquid [C(8)mim]Br affects the growth, reproductive ability, and ATPase activity of earthworms E. foetida., (Copyright (c) 2010 Elsevier Inc. All rights reserved.)

The embryonic developmental toxicity of the ionic liquid (IL) 1-methyl-3-octylimidazolium bromide ([C(8)mim]Br) on the goldfish Carassius auratus was evaluated in this study. First, the 72 h 50% lethal concentrations (72 h-LC(50)) for [C(8)mim]Br in goldfish embryos at the stages of cleavage, early gastrula, closure of blastopore, and heart beating were determined by preliminary acute toxicity tests. After that, fish embryos in different developmental stages (cleavage, early gastrula, closure of blastopore, and heart beating) were exposed to 10.4, 20.8, 41.6, and 104 mg/L of [C(8)mim]Br until their hatching stage. The results of the acute toxicity tests showed that 72 h-LC(50) values at the early cleavage, early gastrula, closure of blastopore, and heart beating stages of development were 208.96, 187.1, 245.03, and 298.33 mg/L, respectively. In the subchronic tests, [C(8)mim]Br exposure prolonged the duration of embryo dechorionation and decreased the hatching rates of the treated embryos compared to control embryos. In addition, [C(8)mim]Br treatment also caused remarkable increases of embryonic malformation and mortality ratio in most treatment groups. Finally, we also found that the embryonic and developmental toxicity of [C(8)mim]Br on fish embryos was dose-response and developmental stage-specific. These results indicate that [C(8)mim]Br has toxic effects on the early embryonic development of goldfish, and the risk to aquatic ecosystem by ILs leaking into the water body must be evaluated in the future., ((c) 2009 Wiley Periodicals, Inc.)

The earthworm Eisenia foetida was exposed to different concentrations of imidazolium ionic liquids with varying chain lengths according to the method of OECD [OECD, 1984. (The Current Organization of Economic and Cooperative Development Acute Earthworm Toxicity Test) Guidelines for the Testing of Chemicals, No. 207. Earthworm Acute Toxicity Tests]. The acute and subchronic toxic effects of [C(8)mim]Br on the activities of acetylcholinesterase (AChE) and cellulase in earthworms were determined under an artificial soil condition. Using filter paper contact tests, the 48 h-LC(50) values of [C(4)mim]Br, [C(6)mim]Br, [C(8)mim]Br, [C(10)mim]Br and [C(12)mim]Br on the earthworm were 73.33, 28.25, 2.69, 0.37 and 0.02 microg cm(-2), respectively. The 7 d-LC(50) of [C(8)mim]Br was 206.8 mg kg(-1) artificial soil (dry weight) and the 14 d-LC(50) was 159.4 mg kg(-1) artificial soil (dry weight), under the condition of artificial soil. After 1 d and 3 d of acute exposure, the activity of AChE was markedly inhibited when compared to the control, while it was increased at 7d. The cellulase activity was elevated significantly in the treatment groups of 20-160 mg kg(-1) after 3 and 7d of acute exposure. The activity of cellulase was also promoted under the subchronic exposure condition in the 10 and 20 mg kg(-1) groups. The experimental results suggest that [C(8)mim]Br may interfere with the nervous function of the earthworms and increase their cellulase activity. These results indicate that [C(8)mim]Br-exposure can affect the metabolized enzyme activity of earthworms at low concentrations and can even cause worm death at high doses, both of which have potential impacts on the soil environment.

This study examined the antioxidant responses of Daphnia magna following exposure to different concentrations of the ionic liquid (IL) 1-octyl-3-methylimidazolium bromide and the 50% LC(50) concentrations of methylimidazolium bromide ILs with different alkyl-chain lengths. Activities of antioxidant defense enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase) and levels of the antioxidant glutathione and the lipid peroxidation by-product malondialdehyde were measured using traditional methods or commercial kits. The concentration and the alkyl-chain length of ILs were found to strongly influence the antioxidant system of D. magna following IL exposure, and exposure to higher IL concentrations and to ILs with longer alkyl chains generally increased the enzyme activities and biomarker levels examined. Therefore, the present study suggests that oxidative stress is involved in the mechanism of IL-induced toxicity in D. magna.

Toxic effects of 1-methyl-3-octylimidazolium bromide ([C8mim]Br) on the early embryonic development of the frog Rana nigromaculata were evaluated. Frog embryos in different developmental stages (early cleavage, early gastrula, or neural plate) were exposed to 0, 45, 63, or 88.2 mg/L of the ionic liquid [C8mim]Br for 96 h. The 96-h median lethal concentration values at the early cleavage, early gastrula, and neural plate stages of development were 85.1, 43.4, and 42.4 mg/L, respectively. In embryos exposed to [C8mim]Br, the duration of embryo dechorionation was prolonged in the early cleavage and neural plate, but not the early gastrula, stages of development compared with control embryos. Embryos in the neural plate developmental stage were found to have the highest mortality rate following [C8mim]Br exposure. These results suggest that [C8mim]Br has toxic effects on the early embryonic development of the frog.

The effects of acute exposure of intraperitoneal injection of aqueous 1-octyl-3-methylimidazolium bromide on the antioxidant enzymes and lipid peroxidation of the treated mouse liver were investigated in the present paper. Thirty mice were treated with 17.9 (0.5 median lethal dose, LD(50)) and 35.7 mg/kg (1 LD(50)) of the ionic liquid or saline solution by intraperitoneal injection for 10h. Significant increase in hepatosomatic index and decrease in liver protein content were found in 1 LD(50) group. No statistically significant change was observed in the activity of superoxide dismutase in both treated groups compared to the control group. In the case of catalase activity, the decrease was recorded only at dose of 1 LD(50). As for the activity of glutathione peroxidase, increase in 0.5 LD(50) group while significant decrease at dose of 1 LD(50) was noted. There was an increase in the activity of glutathione-S-transferase in these two treated groups in comparison to the control. However, no effect on the level of lipid peroxidation was found in the treated groups. These results showed that the acute exposure of aqueous ionic liquid could cause damage to mouse, leading to antioxidant responses in livers of the treated mice.

Abstract: Ionic liquids have recently received considerable attention due to their negligible vapor pressure and substitute for conventional organic solvents. However, their solubility in water and a great deal of literature regarding their toxicity on aquatic organisms have caused much concern in recent years. This study aims to evaluate the cytotoxicity of 1-octyl-3-methylimidazolium chloride ([C8mim][Cl]) on the rat pheochromocytoma (PC12) cell line by cell viability assay and to determine the cytological alterations and damages in PC12 cells after 24h of exposure at the concentrations of 0.07, 0.14, and 0.28mM of [C8mim][Cl]. The results show that [C8mim][Cl] inhibits PC12 cell growth and decreases their viabilities in a remarkable dose-dependent manner, and the 24h EC50 of [C8mim][Cl] for PC12 cells is calculated to be around 0.56mM. Our results also reveal that [C8mim][Cl]-exposure induces DNA damage, sustained increase of intracellular Ca2+, overproduction of reactive oxygen species, gradually exhausted cellular ATP, mitochondrial permeability transition, and apoptosis in PC12 cells. We suppose that mitochondrial permeability transition and mitochondrial dysfunction maybe the major cytotoxicity mechanism of [C8mim]Cl for PC12 cells. [Copyright &y& Elsevier]