Efficiency of Different Methods for dsRNA Delivery in Cotton Bollworm(Helicoverpa armigera)

RNAi trigged by dsRNA not only facilitates the development of molecular biology, but also initiates a new way for pest control by silence of fatal genes. However, one of the key limitations in pest control is lack of the convenient and efficient method for dsRNA delivery. In this study, different dsRNA delivery methods at their own optimum conditions were evaluated comparatively for their efficiency with Helicoverpa armigera as test animal. It was found that the popular one- time injection of larvae with dsRNA could reduce the pupation rate by 43.0% and enhance larva mortality by 11.7%. One- time ingestion of dsRNA did not result in any significant effect on phenotype. Continuous ingestion of in vitro synthesized dsRNA by refreshing the bait diet every day caused 40.4% decrease in successful pupation and 10.0% increase in larval mortality, which was similar as one-time injection. The most efficient method was found to be the continuous ingestion of the bacteria containing dsRNA expressed, which reduced the rate of pupation by 68.7% and enhanced the larval mortality by 34.1%. Further analysis found that dsRNA was degraded faster in midgut juice than in hemolymph. However, the cell of bacteria could protect dsRNA and delay the degradation in the midgut juice of H. armigera. These results throw light on the application of dsRNA in pest management with proper ways.

Novel nanoparticles composed of chitosan and β-cyclodextrin derivatives as potential insoluble drug carrier

This research was aim to develop novel cyclodextrin/chitosan （CD/CS） nanocarriers for insoluble drug delivery through the mild ionic gelation method previously developed by our lab. A series of different β- cyclodextrin （β-CD） derivatives were incorporated into CS nanoparticles including hydroxypropyl-β- cyclodextrin （HP-β-CD）, sulphobutylether-β-cyclodextrin （SB-β-CD）, and 2,6-di-O-methy-βcyclodex- trin （DM-β-CD）. Various process parameters for nanoparticle preparation and their effects on physicochemical properties of CD/CS nanoparticles were investigated, such as the type of CD derivatives, CD and CS concentrations, the mass ratio of CS to TPP （CS/TRP）, and pH values. In the optimal condition, CDICS nanoparticles were obtained in the size range of 215-276 nm and with the zeta potential from 30.22 mV to 35.79 mY. Moreover, the stability study showed that the incorporation of CD rendered the CD/CS nanocarriers more stable than CS nanoparticles in PBS buffer at pH 6.8. For their easy preparation and adjustable parameters in nanoparticle formation as well as the diversified hydrophobic core of CD derivatives, the novel CD/CS nanoparticles developed herein might represent an interesting and versatile drug delivery platform for a variety of poorly water-soluble drugs with different physicochemical properties.