Acute Toxicity,Oxidative Stress And DNA Damage Of Four Task-Specific Ionic Liquids On Zebrafish

Ionic Liquids（ILs）are salts that are completely composed of anions and cations at room temperature,and are considered to be the"green solvent of the 21st century."However,the dissolving power,viscosity,melting point,density and other properties of conventional ionic liquids sometimes cannot meet specific needs.Therefore,researchers have introduced different functional groups to the anions and cations of ionic liquids to change their physicochemical properties to obtain ionic liquids with required functions,namely,Task-Specific Ionic Liquids（TSILs）.TSILs have gradually become research hotspots in the field of ILs.With the extensive synthesis of TSILs,it is inevitable that TSILs will enter the water environment due to waste or improper disposal.However,the current research on the toxicity of TSILs to aquatic organisms is scarce.It is urgent to investigate the safety of TSILs in the aquatic environment and predict its toxic effects on aquatic organisms.In order to evaluate the effects of TSILs on the aquatic environment,zebrafish was selected as the indicator organism to study the toxic effects of TSILs on them.The zebrafish（Danio rerio）is an internationally recognized model animal for developmental biology and is often used for water quality monitoring and life science researchIn this study,four TSILs 1-aminoethyl-3-methylimidazolium tetrafluoroborate（[C₂NH₂MIm]BF₄）,1-methoxyethyl-3-methylimidazolium tetrafluoroborate（[MOEMIm]BF₄）,1-hydroxyethyl-3-methylimidazolium tetrafluoroborate（[HOEMIm]BF₄）,1-hydroxyethyl-3-methylimidazolium nitrate（[HOEMIm]NO₃）,which have been studied more in the field of synthetic applications,are selected as research objects to study their toxic effects on zebrafish.First,the acute toxicity of four TSILs to zebrafish was studied,and the 96 hour median lethal concentration(96 h LC₅₀)was calculated based on the results.Then,the subchronic toxicity test concentration was determined based on the 96 h LC₅₀0 values.The exposure concentrations of[C₂NH₂MIm]BF₄ to zebrafish were 0,5,10,20 and 40 mg/L,and the exposure concentrations of[MOEMIm]BF₄,[HOEMIm]BF₄,and[HOEMIm]NO₃ to zebrafish were 0,1,10,50 and 100mg/L.The levels of reactive oxygen species（ROS）,superoxide dismutase（SOD）,catalase（CAT）,glutathione S-transferase（GST）,malondialdehyde（MDA）and DNA damage in zebrafish liver were tested on days 7,14,21 and 28 after the exposure test.This experiment comprehensively evaluated the oxidative stress and genotoxicity of four TSILs on zebrafish,providing a theoretical basis for a comprehensive understanding of the possible effects of TSILs on aquatic ecosystems,and providing toxicological evidence for application research and the evaluation of functionalized ionic liquids with low toxicity in the future.The specific results of this experiment are as follows:（1）The 96 h LC₅₀0 value of four TSILs（[C₂NH₂MIm]BF₄,[MOEMIm]BF₄,[HOEMIm]BF₄,[HOEMIm]NO₃）are 143.8 mg/L,2492.5 mg/L,3086.7 mg/L and 5016.7mg/L,respectively.The order of the acute toxicity of four TSILs on zebrafish is:[C₂NH₂MIm]BF₄>[MOEMIm]BF₄>[HOEMIm]BF₄>[HOEMIm]NO₃.Compared with the acute toxicity of conventional ionic liquids,ionic liquids have increased toxicity after being functionalized with amino groups,while decreasing toxicity after being functionalized with ether groups and hydroxyl groups.（2）The four TSILs had different subchronic toxicity effects on zebrafish.On the whole,the high-concentration exposure groups（40 mg/L,100 mg/L）of the four TSILs could induce the increase of ROS content in zebrafish,especially on day 28.In addition to[MOEMIm]BF₄,the other three TSILs[C₂NH₂MIm]BF₄,[HOEMIm]BF₄,and[HOEMIm]NO₃ all have inhibitory effects on SOD activity in zebrafish;[MOEMIm]BF₄ and[HOEMIm]BF₄ induced CAT activity in zebrafish was increased while[C₂NH₂MIm]BF₄ and[HOEMIm]NO₃ decreased CAT activity in zebrafish;[C₂NH₂MIm]BF₄ induced a significant increase in GST activity in zebrafish on day 28,and[HOEMIm]BF₄ induced a significant decrease in GST activity in zebrafish on days 14 and 28.（3）The four TSILs all caused some degree of lipid peroxidation and DNA damage in zebrafish liver cells.Among them,[MOEMIm]BF₄ induces the highest degree of lipid peroxidation in zebrafish,the DNA damage induced by[C₂NH₂MIm]BF₄ in zebrafish is the most serious.（4）By calculating the integrated biomarker response index（IBR）,the order of the sub-chronic toxicity effects of four TSILs on zebrafish is:[MOEMIm]BF₄>[C₂NH₂MIm]BF₄>[HOEMIm]BF₄>[HOEMIm]NO₃.The four TSILs showed different sensitivities to various experimental indicators.The more sensitive indicator in the toxicity test of[C₂NH₂MIm]BF₄on zebrafish was the DNA damage.The more sensitive indicators in the toxicity experiments of[MOEMIm]BF₄ and[HOEMIm]BF₄ on zebrafish were ROS and lipid peroxidation,and the more sensitive indicators in the toxicity experiments of[HOEMIm]NO₃ on zebrafish was CAT.