Improvement of RNAi efficiency by delivering of dsRNA formulated with cell-penetrating disulfide polymer in the fall Armyworm, Spodoptera frugiperda

RNA interference (RNAi) has shown excellent potential for pest management worldwide. However, the application of RNAi against insects can be inefficient and unreliable. Finding a better delivery system is a crucial factor for enhancing RNAi efficacy. Here, we present a novel and effective approach of conjugating double-stranded RNA (dsRNA) with a cell-penetrating disulfide polymer (CPD) to improve dsRNA stability and RNAi efficiency. The fall armyworm (FAW), Spodoptera frugiperda, is a globally agricultural insect. Chitin synthase B (CHSB) and methoprene-tolerant (Met) genes, which are essential for the development and growth of FAW, were selected as target genes. The CPD was synthesized using a two-step method for dsRNA delivery. The synthesized CPD/dsRNA complex protected dsRNA from nuclease degradation. The biological application of CPD in Sf9 cells demonstrated low cytotoxicity and high cell viability. Moreover, the CPD-loaded dsRNA entered the cells within 6 h. Bioassays of FAW showed that the relative expression levels of the CHSB and Met genes were reduced. Specifically, at 72 h, the relative expression levels of the CHSB and Met genes were 48.14 % and 37.60 % of those in the control group, respectively. The weight and body length of the larvae decreased significantly, and the mortality rate of CPD/dsCHSB reached 30 %. This CPD was demonstrated for the first time to have excellent delivery performance in insects and is expected to become a new and effective tool for pest control, representing a significant advancement in pest management.