The toxic differentiation of micro- and nanoplastics verified by gene-edited fluorescent Caenorhabditis elegans

The increased emission and accumulation of micro- or nanoplastics (M-NPs) have posed a severely threaten to organisms in the environment. Though the toxicity of M-NPs has been observed in many species, the fundamental factors determining the biotoxicity are rarely expounded on. In this work, typical polystyrene (PS) M-NPs were set up with a multiparameter variation in size gradient, surface charge contrast and concentration variant, and evaluated by the Caenorhabditis elegans (C. elegans) model. From the endpoints of body length, brood size, survival rate and lifespan, an adverse effect was found on the growth and development of C. elegans caused by PSs. In general, the toxicity of PS was found to be concentrated- and size-dependent, with 100 nm positively charged nano-PS having the highest physio-toxicity. Monitoring by fluorescent imaging, it showed that positively charged nano-PS was mainly ingested and accumulated in the intestinal tract of C. elegans. In addition, the penetrated PS induced severe biological stress reactions with the increase of reactive oxygen species (ROS) and lipofuscin. Furthermore, the following expression of antioxidation-related enzymes was activated in vivo as indicated by the GFP-labelled C. elegans. All the results supplied visually toxic parameters of M-NPs to organisms, which sheds light on the biosecurity and ecological risks of M-NPs in the future.