Enhancing the safety of a chitosan-based nanopesticide in zebrafish through interactions with water microorganisms

Understanding the impact of chitosan-based nanoparticles (NPs) on ecological systems is vital for assessing their environmental behavior and safety. In this study, we investigated the effects of pyraclostrobin@chitosan-based nanoparticles (NPs.PYR) on microbial communities in a pond. NPs.PYR significantly impacted the abundance of microbial communities in the pond, compared with the commercial pesticide suspensions. We employed Chlorella sp. as a representative microorganism to explain this phenomenon and found that the NPs and NPs.PYR treatments induced a rapid decrease in the abundance of Chlorella sp. This phenomenon can be attributed to the electrostatic interaction between the NPs and microorganisms, along with the affinity of the microorganisms' extracellular polymers to the chitosan-based NPs, resulting in the cosettlement of the microorganisms with these NPs. The NPs.PYR migrated from the overlying water to the sediment, decreasing the PYR concentration in the overlying water. The mortality of zebrafish specimens exposed to NPs.PYR was significantly lower than that of the specimens exposed to pyraclostrobin suspension concentrate. These results suggest that the prepared chitosan-based nanopesticide tends to aggregate with microorganisms, leading to cosettlement and reduced pesticide levels in the overlying water, thus enhancing the safety of nontarget animals.