Toxicological Effects Of Polystyrene Micro-nano Plastics Based On Caenorhabditis Elegans Model

Microplastics are small plastic particles with a diameter of less than 5 mm,and nanoplastics(≤1μm)are further decomposed from microplastics in the environment.Micro-nano plastics(M-NPs)are characterized by small particle size,light texture and easy transfer.They are widely accumulated and spread in the environment and can cause mechanical damage,reproductive defects and a series of stress effects.However,the key factors determining the toxicity of M-NPs are unknown and the exact toxicity mechanism has not been formed.Therefore,it is necessary to study the toxicology of M-NPs.In this study,Caenorhabditis Elegans was used as a model organism to establish a toxicity evaluation model,and to study the toxicity effects of polystyrene M-NPs,verify the key toxicity factors and analyze the toxicity mechanism.In particular,M-NPs with different surface charges,particle sizes and concentrations were designed and exposed to Caenorhabditis elegans,and systematically studied the distribution and accumulation of PS M-NPs,growth and development toxicity of Caenorhabditis elegans.Furthermore,the changes of reactive oxygen species(ROS),lipofuscin,glutathione S-transferase and superoxide dismutase were analyzed by co-localization using transgenic nematodes labeled with fluorescent protein.According to the above research contents,the concentration threshold,particle size dependence and charge difference of M-NPs toxicity were revealed,and the molecular pathway of M-NPs toxicity effect was clarified,providing scientific basis for the environmental health and ecological risks of M-NPs.The main results include:The inhibition degree of growth and development of nematodes exposed to PS with different sizes showed a trend of 100 nm>500 nm>2000 nm,indicating that the smaller particle size,the more serious the adverse effects.With the exposure of PS at different concentrations,the body length of nematodes was significantly inhibited,the brood size and survival rate decreased,and the life span of nematodes was shortened,indicating that the toxicity of PS increased with the increase of PS concentration.Through fluorescence co-location analysis,PS was easy to be absorbed and accumulated by C.elegans,and could be clearly seen in C.elegans.With the increase of concentration,PS was distributed in C.elegans and gradually spread throughout the body.In addition,by monitoring the oxidative stress response of GFP labeled transgenic nematodes,it was found that positive charge PS-NH2 was more toxic than negative charge PS-COOH.PS-NH2 and PS-COOH can induce nematodes to produce excessive ROS and lipofuscin.PS-NH2 disrupted the antioxidant system of nematodes,resulting in oxidative damage.