Abstract
In this study, the use of dendrimer-coated carbon nanotubes (CNTs) as a delivery vehicle for dsRNA was assessed in Tribolium castaneum. Exposure to low dosages of polyamidoamine dendrimer carbon nanotubes (PAMAM-CNTs) did not affect T. castaneum larval mortality. Expression of key apoptotic factors, Dronc (Tc12580), Dredd (Tcn-like, Tc014026) and Buffy, (Tcinhib apop1), which can act as toxicity indicators, were not altered in T. castaneum larvae following injection of PAMAM-CNTs. The level of knockdown of two target genes, α-tubulin and mitochondrial RNA polymerase (mtpol), were significantly increased when larvae were injected with double-stranded RNA bound to CNTs (PAMAM-CNT-dsRNA), compared to those injected with target dsRNA alone. PAMAM-CNTs were visualised in cellular vacuoles and in the cell nucleus. Increase occurrence of a blistered wing phenotype was found in a subset of PAMAM-CNT-dsRNAαtub injected larvae, relative to the level seen in larvae injected with naked dsRNAαtub alone. These results suggest that the use of functionalised CNTs for dsRNA delivery could increase the efficacy of RNA interference in insect pest species.
Highlights
RNA interference (RNAi) is a promising tool for the control of insect pests
polyamidoamine dendrimer (PAMAM)-carbon nanotubes (CNTs) alone were harmful to T. castaneum, 4th instar larvae were micro-injected with PAMAM-CNTs ranging in concentration from 10–200 μg/mL or with control dye solution
No increased mortality was seen for any PAMAM-CNT dose compared to dye injected control larvae at 24 h (P = 0.851) or 48 h (P = 0.288) (Fig. 1)
Summary
RNA interference (RNAi) is a promising tool for the control of insect pests. Introduction of exogenous doublestranded RNA (dsRNA) is effective at triggering gene knockdown and associated phenotypes in many problem pest species such as the Western Corn R ootworm[1], the Colorado potato b eetle[2] and the Varroa m ite[3]. New developments in dsRNA delivery methods to crop pests, such as dsRNA expression in transgenic p lants[4] and foliar application[5], offer the possibility of dsRNA-based insecticides[6] Despite this promise, there is notable variation in RNAi response between insect s pecies[7], with some, such as many lepidopterans[8], unable to mount a strong RNAi response to dsRNA. Relatively low weight makes them ideal, for applications in nanomedicine and drug delivery Due to their hydrophobic nature, pristine CNTs cannot be functionally integrated into biological systems unless they undergo surface functionalization to both allow their suspension and become more biocompatible[26]. As well as being easy to rear in laboratory settings the species has a well-characterised genome[32] and displays a robust systemic RNAi response[33], which can even be spread to offspring[34]
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