Comparative evaluation of chitosan-based and star polycation nanocarriers for enhanced RNAi efficacy targeting CmFibL in Cnaphalocrocis medinalis.
BACKGROUND: The rice leaf folder, Cnaphalocrocis medinalis, causes substantial rice yield losses through larval leaf-rolling behavior. RNA interference (RNAi) offers a sustainable alternative, but its application in Lepidoptera is hindered by dsRNA degradation and poor cellular uptake. This study developed nanocarrier-mediated dsRNA delivery to overcome these limitations. RESULTS: Three nanocarriers - chitosan (CS), chitosan-tripolyphosphate (CS-TPP), and star polycation (SPc) - were compared for enhancing RNAi efficiency targeting the C. medinalis fibroin light chain gene (CmFibL). CS-TPP and SPc achieved 61% and 55% silencing efficiency, respectively, representing 2.7-fold improvement over naked dsRNA (23%). All nanocarriers protected dsRNA from RNase A (30 min) and midgut fluid (6 h) degradation. CmFibL knockdown caused severe silk defects, prolonged pupal duration by 23%, reduced pupal weight by 33%, and decreased leaf-rolling damage by 31% in glasshouse cage trials. Transcriptomics revealed down-regulation of amino acid metabolism and activation of endoplasmic reticulum (ER) stress and immune responses. No off-target effects were detected in human genome, nor in any predators or parasitoids sharing the same ecological niche. CONCLUSION: CS-TPP and SPc nanocarriers effectively enhance RNAi efficiency in a Lepidopteran pest. Targeting CmFibL disrupts silk-mediated feeding shelters with minimal ecological risk, providing a practical framework for field application of RNAi-based biopesticides against leaf-rolling rice pests. © 2026 Society of Chemical Industry.