Effective delivery and selective insecticidal activity of double‐stranded RNA via complexation with diblock copolymer varies with polymer block composition

Abstract

BACKGROUNDChemical insecticides are an important tool to control damaging pest infestations. However, lack of species specificity, the rise of resistance and the demand for biological alternatives with improved ecotoxicity profiles means that chemicals with new mode‐of‐actions are required. RNA interference (RNAi)‐based strategies using double‐stranded RNA (dsRNA) as a species‐specific bio‐insecticide offer an exquisite solution that addresses these issues. Many species, such as the fruit pest Drosophila suzukii, do not exhibit RNAi when dsRNA is orally administered, due to degradation by gut nucleases and slow cellular uptake pathways. Thus, delivery vehicles that protect and deliver dsRNA are highly desirable.RESULTSIn this work, we demonstrate the complexation of D. suzukii‐specific dsRNA for degradation of vha26 mRNA with bespoke diblock copolymers. We study the ex vivo protection of dsRNA against enzymatic degradation by gut enzymes, which demonstrates the efficiency of this system. Flow cytometry then investigates the cellular uptake of Cy3‐labelled dsRNA, showing a 10 fold increase in the mean fluorescence intensity of cells treated with polyplexes. The polymer/dsRNA polyplexes induced a significant 87% decrease in the odds of survival of D. suzukii larvae following oral feeding, only when formed with a diblock copolymer containing a long neutral block length (1:2 cationic block/neutral block). However, there was no toxicity when fed to the closely related D. melanogaster.CONCLUSIONThus, we provide evidence that dsRNA complexation with diblock copolymers is a promising strategy for RNAi‐based species‐specific pest control, however, optimisation of polymer composition is essential for RNAi success.This article is protected by copyright. All rights reserved.

Engineered Resistance to Tobamoviruses

“…More recently, various synthetic organic polymers with cationic properties have been investigated as protectants and slow-release agents for biologically active double-stranded RNA under challenging conditions (e.g., the plant phylloplane or rhizosphere, insect guts, etc.) [120,121]. However, the use of these formulations has been proposed mainly or control of invertebrate pests and at this time there do not seem to be any reports of these polymers being used as carriers of antiviral double-stranded RNA molecules.…”

Engineered Resistance to Tobamoviruses

“…More recently, various synthetic organic polymers with cationic properties have been investigated as protectants and slow-release agents for biologically active double-stranded RNA under challenging conditions (e.g., the plant phylloplane, the rhizosphere, insect guts, etc.) [120,121]. However, the use of these formulations has been proposed mainly for control of invertebrate pests and at this time there do not seem to be any reports of these polymers being used as carriers of antiviral double-stranded RNA molecules.…”

Optimizing toxic bait composition and application to control Drosophila suzukii

“…Additionally, the use of nanoparticles (e.g. chitosan, liposomes and cationic dendrimers) or nano vectors improve dsRNA delivery and efficiency by protecting dsRNAs (Yan et al, 2021;Pugsley et al, 2024). Also the use of hydrophilic diblock copolymers have been effective in encapsulating and transporting dsVha26 and inducing mortality in D. suzukii larvae, with one block being waterattracting and the other being water-repellent, (Pugsley et al, 2024).…”