pH/Enzyme-responsive nanocarrier pesticide delivery system: Realizing targeted release in pest gut for enhanced Apis cerana safety

Abstract

The application of pesticides has significantly reduced the danger of pests to crops. However, the adverse effects of pesticides on non-target organisms pose a significant environmental threat. Here, we constructed bio-based polymer nanoparticles of indoxacarb (IDC) that can be enzymatically released (trypsin and chymotrypsin) according to the intestinal pH of Spodoptera frugiperda and Apis cerana, thereby improving the safety of indoxacarb to non-target organisms. The results showed that the average diameter of IDC@ZOC NPs was 170.9 nm and had dual responses to pH and enzyme activity. In the simulated S. frugiperda intestinal conditions (pH 8.0–10.0), the nanoparticles disintegrated rapidly under higher trypsin/chymotrypsin activities and released a large amount of drugs. Conversely, under simulated honeybee intestinal conditions (pH 4.5–6.5), nanoparticles aggregated under acidic conditions, reducing the rate at which the nanoparticles were hydrolyzed by proteases. Bioassay results showed that IDC@ZOC NPs were 1.9 times as toxic to S. frugiperda larvae as IDC WP, caused severe damage to the midgut and affected larval growth, development and oxidative stress activity. Notably, the toxicity of IDC@ZOC NPs to honeybees was reduced by 3.09 times compared to IDC WP, significantly reducing the effects on honeybee growth and development. In addition, the increased levels of DCJW in S. frugiperda larval midgut confirmed the enhanced efficacy of IDC@ZOC NPs. In summary, our results propose a nanopesticide delivery system that responds to changes in pH and proteases in the guts of pests and honeybees, providing a new strategy for pest management through an innovative pesticide delivery system.