Natural polyphenols regulated emamectin self-assemblies for synergistic insecticidal activity and mitigation of environmental risks

Co-delivery of multiple active ingredients has emerged as a promising strategy for pest control to achieve effective utilization and reduction of environmental risks of pesticide. Due to the facile preparation process, high loading rate, and excellent physicochemical properties, carrier-free self-assembly has been used for efficient co-delivery of multi-components to improve the efficacy and environmental safety of pesticides. Natural plant polyphenols (PPs) not only possess remarkable ultraviolet shielding capacity and strong surface binding ability but also have pH-dependent redox properties. Herein, three PPs are utilized as green functionalized modules to co-assemble respectively with biopesticide emamectin (EMA) to form core-shell structured nanoparticles (EMA-PPs NPs) via non-covalent interactions without the use of any adjuvants, in which PPs and EMA are protected from off-target losses in the environment and exert synergistic insecticidal effects with different insecticidal mechanisms. The prepared EMA-PPs NPs show excellent physicochemical characteristics including surface activity, max retention on the surface of crop leaves, photostability, and pH-dependent redox activity. Additionally, bioactivity and safety evaluations reveal that EMA-PPs NPs with prolonged duration have significantly synergistic activity against Ostrinia furnacalis larvae by more than 3-fold compared to commercial formulation of EMA, and reduce the toxicity of EMA to plants and zebrafish. Therefore, this work will provide a promising strategy for developing biopesticide nanoformulations with improved efficacy and environmental safety.