Toxic Effects Of Ionic Liquid On Planarian Dugesia Japonica

Ionic liquids(ILs), which completely consist of ions, are one category of fluid chemicals at roomtemperature. Due to its unique characteristics, such as negligible vapor pressure, perfect electricconductivity, high thermal stability and excellent solvation ability, it will be the "green" sbustitute oftraditional organic solvent. With the popularization and application in various fields, their biologicaltoxicity and environmental risk assessment have been paid more and more attention. Freshwater planariansinhabiting in clear springs and lakes are very sensitive to the toxic and teratogenic factors in theenvironment. Thus they are one kind of good indication species of water quality. In addition, they arewidespreading, easy to collect, convenient to lab rear and low cost. So the freshwater planarian toxicologyhas been thriving lately. In view of the importance of biological toxicity study of ionic liquids and theadvantages of freshwater planarians being experimental animals of toxicology studies, exploring the toxiceffects of ionic liquids on freshwater planarians is completely feasible and has its importance and necessityas well.In this study, we select one species of freshwater planarian-Dugesia japonica which is widelydistributed in China as the test animal, one ionic liquids delegate1-methyl-3-octyl imidazolium bromide([C₈mim]Br) as the toxic factor. The tissue toxicity, cell toxicity, biochemical and genetic toxicity of[C₈mim]Br on D. japonica have been explored from individual level, tissue level, cytogenetics level,biochemical level and DNA molecular level via the acute toxicity test, paraffin-section technique,micronucleus and chromosome aberration test, antioxidant enzyme activity determination and comet assay.This is the first and systematical study of biological toxic effects of IL on freshwater planarian, and it willprovide fundamental information for the final environmental risk assessment of ILs. The main conclusionswe have drawn are as follows:1. The50%lethal concentration (LC50)(7d) of ionic liquids [C₈mim]Br on Dugesia japonica is220.19mg/L, and its95%confidence limit is194.72～249mg/L. This value is slightly higher than someother aquatic organisms, such as Daphnia magna, goldfish etc;2. In the range of163.84-625mg/L,[C₈mim]Br can cause distort, contraction, fade, head and tailmalformations or even disintegration of D. japonica. It can also cause movement disorders (random motion) and almost stillness of D. japonica. This indicates [C₈mim]Br has biological toxicity onfreshwater planarians;3. In the range of140.8-275mg/L,[C₈mim]Br can cause D. japonica to show various degrees oftissue damages,such as body surface mucus layer injury, nemaline reduce, separation of epithelial layer andthe muscular layer, thinning of muscle layer and cavity in parenchymal tissue. The injury severity showIL concentration-related and treatment time-related. This suggests [C₈mim]Br can cause certain tissuetoxicity on freshwater planarians;4. In the range of100-200mg/L,[C₈mim]Br can cause Certain concentrations of ionic liquidcan cause chromosome aberrations of D. japonica, such as haploid, aneuploidy chromosome deletions,chromosome gap, chromosome ring, chromosome bridge, chromosome adhesion, lagging chromosomes etc.Micronucleus and other nucleus abnormity such as nuclear concave and giant nucleus are also obvserbed.All of these indicate [C₈mim]Br has certain cytotoxicity on freshwater planarians;5. In the range of55-220mg/L,[C₈mim]Br cause the antioxidant enzyme system of D. japonicachange. Glutathione peroxidase (GPX), glutathione-S transferase (GST), catalase (CAT) and superoxidedismutase (SOD) activity change with the change of IL treatment concentration and time. The contents ofglutathione (GSH) and malondialdehyde (MDA) in planarian tissue also change correspondingly. Thisindicates [C₈mim]Br has certain biochemical toxicity on freshwater planarians;6. In the range of100-200mg/L, DNA damage can be observed via single cell gelelectrophoresis(SCGE), it leads to the comet tail phenomenon. With the exposure concentration increased,a dose-effect relationship can be abserved. This indicate that [C₈mim]Br has genetic toxicity on freshwaterplanarians.