Synthesis and characterization of a novel stimuli-responsive zein nano delivery system for the controlled release of emamectin benzoate

Abstract

Lepidopteran insects constitute one of the largest fractions of animals on earth, but most are considered pests in their relationship with humans. In particular, the midgut is the primary site of digestion and absorption, which is alkaline and contains many alkaline proteases. In current pesticide preparation, zein can be used as an ideal carrier material due to its antioxidation properties, biocompatibility, low cost, and adhesion. Moreover, zein is stable in gastric acid but can be soluble in alkaline solution or degraded by alkaline proteases in the intestine. Herein, a pH/enzyme dual-responsive zein–EMB–nanocapsule (zein-EMB-NC) system was prepared to enhance the pesticide's adhesion, target wettability, stability, anti-photolysis, and stimuli-responsive controlled release properties. Scanning electron microscopy, transmission electron microscopy, and dynamic light scattering were applied to investigate their structural characteristics and stability, from which it was found that zein-EMB-NC formed uniform nanoparticles with an average diameter of 156.9 ± 0.6 nm and had excellent stability in aqueous solution. As confirmed by ultraviolet-visible spectroscopy, the anti-UV properties of zein-EMB-NC revealed that the presence of zein could protect EMB from UV photolysis. The foliar surface adhesion and wettability performance of zein-EMB-NC are significantly improved through hydrophobic interactions and hydrogen bonding. The toxicity of zein-EMB-NC to Spodoptera exigua (Hübner) was significantly higher than that of three commercially available formulations tested. The application of foliar spraying on peanuts against Spodoptera exigua (Hübner) shows that a 60% dose of zein-EMB-NC retained a control efficacy similar to that of commercialized samples. Overall, this novel zein-EMB-NC has broad prospects in crop protection by improving insecticidal activity and reducing pesticide loss.