Polyethyleneimine-modified mesoporous silica nanoparticles loaded with methoprene increased the insecticidal efficacy against Tribolium castaneum

Surface-modified mesoporous silica nanoparticles (MSNs) are regarded as efficient and promising nanocarriers in novel pesticide delivery. In this study, MSNs were synthesized and functionalized with low molecular weight polyethyleneimine (PEI), after which methoprene was loaded by adsorption. Detailed investigations showed that MSNs-PEI exhibited excellent encapsulation efficiency (53.33 %) and loading efficiency (21.03 %) for methoprene. The release behaviors of methoprene from Met@MSNs-PEI showed an initial rapid release stage followed by a sustained release stage. Methoprene was released faster in alkaline solutions compared with in acidic and neutral media. The kinetic study revealed that the release data fit best with the Korsmeyer-Peppas model. Additionally, Met@MSNs-PEI exhibited negligible toxicity towards S2 cells and low acute toxicity to zebrafish. Bioassay results showed that Met@MSNs-PEI exhibited significantly better insecticidal activity against Tribolium castaneum larvae than methoprene alone under the same doses of active ingredient applied, which obviously enhanced the utilization efficiency. Moreover, fluorescence microscope observations confirmed the successful internalization and distribution patterns of FITC-labeled MSNs-PEI in T. castaneum larvae, indicating that MSNs-PEI could serve as nanocarriers to deliver insecticides. RNA-seq analysis and qRT-PCR validation showed that MSNs-PEI-loaded methoprene resulted in the downregulation of genes related to detoxification, hormone synthesis, and cuticle biosynthesis, which inhibited insect growth and development. Therefore, MSNs-PEI nanoparticles provided an effective delivery system for methoprene.