Effects Of Multi-walled Carbon Nanotubes On The Enantioselective Accumulation And Toxicity Of Indoxacarb In Zebrafish

As an important guarantee for the stable harvest of crops,pesticides are the most direct,economical and effective measures for the prevention and control of harmful organisms in modern agricultural production,and have an irreplaceable role.However,with the sharp increase in the use of pesticides and the unreasonable application methods,there are many negative impacts on the ecological environment and human health.The proportion of pesticides in chiral pesticides has increased year by year.Due to the enantiomers differences in chiral enantiomers in terms of biological activity,toxicity,degradation and metabolic behavior,the stereoselective behavior of chiral pesticides in the environment has gradually attracted people's attention.At the same time,with the rapid development of nanotechnology,some nanomaterials with unique properties have been widely used in many fields such as biomedicine and environmental management.These nanomaterials inevitably enter the environment,which also increases the possibility of coexistence of chiral pesticides and nanomaterials in the environment.Therefore,the effects of nano-materials on the enrichment and toxicity of chiral pesticides in organisms at the enantiomeric level,can be studied to more accurately and realistically assess the environmental risks that may arise from coexistence in the environment.In this study,chiral pesticides,indoxacarb and multi-walled carbon nanotubes(MWCNTs)were selected as the research objects,zebrafish is the test organism,the effect of multi-walled carbon nanotubes on the selective accumulation and toxicity of indoxacarb in zebrafish was studied.The main contents and results are as follows:(1)A method for the determination of indoxacarb enantiomers in zebrafish and water by high performance liquid chromatography tandem mass spectrometry was established.The results showed that the linear relationship was good in the range of 0.0025-1 mg/L,and the matrix effect was not obvious.The recovery rates of the two enantiomers of indoxacarb in zebrafish were between 81.2% and 96.5%,and the relative standard deviations were between 2.42% and 9.01%.The recovery rates in water were between 80.5% and 9.46%,and the relative standard deviations were between 5.12% and 9.37%.The LOD is 0.0001 mg/L and the LOQ is 0.005 mg/L.(2)Based on the above methods,single and combined long-term exposure tests of indoxacarb and multi-walled carbon nanotubes were conducted to study the effects of MWCNTs on the accumulation and elimination of indoxacarb in zebrafish.The results showed that zebrafish has significant enantioselectivity for the accumulation of chiral pesticide indoxacarb,Priority accumulate indoxacarb peak-2,BCF value reached 305.14 at 28 days,and almost no accumulate indoxacarb peak-1,BCF value is only 22.81.The EF value increased from 0.537 at the initial exposure to 0.931.However,the selective accumulate of indoxacarb enantiomers in zebrafish did not change after the combined exposure with 0.05mg/L MWCNTs and 0.5mg/L MWCNTs,also priority accumulate indoxacarb peak-2,and EF values rose from 0.571 and 0.625 at the beginning of exposure to 0.923 and 0.926,respectively,indicating that MWCNTs have no effect on the enantioselectivity of zebrafish on chiral pesticide indoxacarb accumulation.However,compared with the single group of indoxacarb peak-2,the presence of MWCNTs significantly increased the accumulation concentration of indoxacarb peak-2 in the combined exposure group of indoxacarb peak-2 and 0.5 mg/L MWCNTs.BCF value reached 504.61 at 28 days,indicating that MWCNTs will increase the accumulation ability of zebrafish to indoxacarb peak-2.In the elimination phase,the average degradation half-life of indoxacarb enantiomers was 1.30 days,indicating that the elimination of indoxacarb enantiomers in zebrafish was very fast,and MWCNTs had no effect on the elimination of indoxacarb in zebrafish.During the test,there was no interconversion between the enantiomers of indoxacarb.(3)The toxic effects of single and combined exposure of indoxacarb and MWCNTs by studying the changes of antioxidant enzyme activities and oxidative stress biomarkers in brain and liver of zebrafish.The results indicate that indoxacarb is toxic to zebrafish and also exhibits enantioselectivity.For example,indoxacarb induced a significant increase in CAT activity in the liver of zebrafish,and there was a significant difference in the increase in CAT activity induced by the indoxacarb racemate and indoxacarb enantiomers.Compared with the control group,zebrafish brain and liver exposed to MWCNTs alone can also cause oxidative stress toxicity.The combined exposure of indoxacarb to MWCNTs indicates that MWCNTs can alter the toxicity of indoxacarb in zebrafish,For example,on the 14 th day of exposure,the amount of SOD activity in the liver of zebrafish exposed to the indoxacarb,indoxacarb peak-1,and indoxacarb peak-2 was indoxacarb peak-2 > indoxacarb peak-1 > indoxacarb racemate,and after exposure with high concentration MWCNTs,the activity of SOD is indoxacarb peak-1> indoxacarb racemate> indoxacarb peak-2.This study investigated the effects of multi-walled carbon nanotubes on the selective enrichment and toxicity of indoxacarb in zebrafish.To provide a theoretical basis for the future evaluation of the potential risk exposure of nanomaterials and chiral pesticides to aquatic organisms and the ecological environment.