Enhanced insecticidal activity and bioavailability of thiacloprid from pH-responsive porous MPN(Fe)@ZIF-8 nanocarrier

The application of ZIF nanomaterials as controlled release agents for pesticides holds significant promise in enhancing pesticide utilization efficiency, prolonging their effectiveness, and minimizing pesticide residues. However, the loading efficiency of single ZIF is limited and susceptible to external stimuli. Therefore, in order to improve the loading rate of the material and enhance the bioavailability of the pesticide, a novel porous nanocarrier (MPN (Fe) @ZIF-8) was prepared for loading the neonicotinoid pesticide thiacloprid (THIA) by combining the biocompatible material metal polyphenol network (MPN) with ZIF-8 using the co-precipitation method and layer-by-layer self-assembly strategy. Through the selection of carrier materials and optimization of loading conditions, MPN (Fe) @ZIF-8 with irregular coral-like structure was obtained, which had high specific surface area (82.15 m 2 /g) and excellent load ratio (18.93 %). In addition, with the aim of preventing pesticide leakage, polyethyleneimine (PEI) was added to the nanocarrier system as a sealing agent, and porous ZIF nanopesticides with pH-responsive properties (MPN (Fe) @ZIF-8@THIA@PEI) were prepared. In vitro release experiments showed that MPN (Fe) @ZIF-8@THIA@PEI favoured the release of THIA (72.33 % cumulative release) under alkaline conditions (pH = 8.6), whereas it was delayed (42.24 % cumulative release) under acidic conditions (pH = 3.6). It was noteworthy that MPN (Fe) @ZIF-8@THIA@PEI has a higher lethality rate (89.04 %) against B. tabaci than commercial THIA reagents (66.67 %). Furthermore, after 8 h of UV irradiation, the residual pesticide in the commercial THIA reagent was only 11.27 %, while that in MPN (Fe) @ZIF-8@THIA@PEI remained at 73.98 %. Hence, this work provides new ideas for the development of green and environmentally friendly stimuli-responsive porous controlled release agents.