Study On The Impact Of Copper Nanoparticles On The Biotoxicity Of Microplastics With Different Sizes

In recent years,the pollution of microplastics(MPs)in aquatic environments and the adverse effects on aquatic organisms have attracted increasing attention.MPs in water bodies may interact with pollutants such as nanomaterials(NMs)and be ingested by organisms,resulting in combined toxic effects.However,there are conflicting results regarding the combined toxicity of MPs and NMs in the current studies,and the toxicity mechanism has not been clearly explained at the molecular level.Therefore,we need to evaluate the toxic effects of MPs exposure alone and combined exposure with NMs and predict their toxicity mechanisms.We conducted zebrafish acute toxicity experiments and used transcriptome sequencing to assess whether the presence of copper nanoparticles(Cu-NPs)would affect the toxic effects of polystyrene microplastics(PS-MPs;0.07,0.7,and 7 ?m)on zebrafish.The results of acute toxicity experiments indicated that the acute toxicity of MPs with three sizes was 7 ?m MPs>0.07 ?m MPs>0.7 ?m MPs.The GO enrichment analysis of the differentially expressed genes(DEGs)showed that both 0.07 and 7 ?m MPs acted on the chromosome and significantly affected the cell cycle process by affecting palmitoyl hydrolase activity;while 0.7 ?m MPs acted on the extracellular space and significantly affected the activity of endopeptidase inhibitors to affect the cholesterol transport process.The presence of Cu-NPs only changed the GO enrichment results of 7 ?m MPs exposure,that is,the combined exposure of Cu-NPs and 7 ?m MPs acted on the extracellular region and significantly affected the cholesterol transport process by affecting the activity of cholesterol transporters.And the pathway enrichment analysis of DEGs revealed that PS-MPs and Cu-NPs have two different modes of toxic effects on zebrafish.The single exposure of 0.07 ?m MPs and 7 ?m MPs,and the combined exposure of Cu-NPs and 0.07 ?m MPs caused the inhibition of "cell cycle" pathway.The inhibition of the expression of the related coding genes of MCM complex and cyclin hindered the transformation of different phases in the cell cycle,inhibited the normal formation of spindle and spindle assembly checkpoints,induced mitotic catastrophe,and ultimately affected cell proliferation,individual growth and development.However,the single exposure of 0.7 ?m MPs and the combined exposure of Cu-NPs and 0.7 ?m MPs,Cu-NPs and 7 ?m MPs abnormally activated the "hemostasis" pathway.And the up-regulation of genes encoding platelet dense granules,? granule components and fibrinogen promoted the activation and aggregation of a large number of platelets,activated the production of fibrinogen and promoted the formation of fibrin clots,which proved that the tissues and organs of zebrafish were being damaged and repaired.In addition,the presence of Cu-NPs only changed the toxicity-related pathways induced by 7?m MPs from "cell cycle" into "hemostasis",but not of 0.07 and 0.7 ?m MPs.In this study,the interaction between Cu-NPs and MPs in aquatic environments was considered,and transcriptomics was innovatively used to analyze the influence of the interaction and reveal the impact of the presence or absence of Cu-NPs on the toxicity mechanisms induced by MPs.These findings contribute to a clearer understanding of the potential toxicity of MPs and NMs to aquatic organisms,and provide ideas and research foundations for the combined effects of MPs and other pollutants in actual ecosystems.