(741f) Loading and Mobility of RNA in Porous Silica Nanoparticles for  Delivery to Insects

RNA interference (RNAi) technology, which enables the suppression of targeted genes, is of wide interest to insect pest management through the silencing the genes that relate to the insect fitness or mortality. Identifying efficient methods to deliver the dsRNA to insects is the key challenge to achieve effective RNAi. Porous silica nanoparticles (pSNPs), which have tunable pore morphology, large surface area, biocompatibility and ease of surface functionalization, are potential carriers for biomolecules. The goal of this work is to demonstrate the loading, release, and protection of RNA in porous silica nanoparticles. pSNPs with pore sizes appropriate for biomolecule loading have been successfully synthesized to encapsulated the dsRNA within the pores. The silica particles were further functionalized with aminosilanes, providing amine groups with positive charge on the surface necessary to load negatively charged nucleic acids. To investigate the RNA interaction with the particles, direct visualization of the loading of RNA on micron-sized silica particles with similar pore sizes to the pSNPs was performed under confocal laser scanning microscopy. The interaction of dsRNA with the pSNP and the accessibility of the pores of the pSNP can be described from the diffusivity (mobility) of the dsRNA in RNA-loaded pSNPs. Using Fluorescence Recovery after Photobleaching (FRAP), the effect of both pore size (nonporous, 3.6 nm, 7.4, and 11.8 nm diameter) and length of dsRNA (84 bp and 282 bp of fragments within the inhibitor of apoptosis (IAP) genes of Spodoptera frugiperda) on the diffusivity at the surface and in the core of dsRNA-loaded pSNPs has been quantified. The importance of pores to a mobile dsRNA network is demonstrated by the lack of measurable mobility for both lengths of RNA on nonporous materials. In addition, when the dsRNA could not penetrate the pores, dsRNA mobility is also not measurable at the surface of the particle. Thus, the pores seem to serve as a “sink” in providing a mobile network of dsRNA on the surface of the particle. The mobility of dsRNA in the nanopores of the pSNPs is expected to have a functional effect on delivery of dsRNA to insects and the delivery of the IAP genes to Spodoptera frugiperda using pSNPs is interpreted from loading and mobility as a function of pore size. This work successfully demonstrates the loading of RNA on functionalized pSNPs and identified factors that affects RNA loading and releasing, which provides basis for the delivery of RNA-loaded silica particles in vivo.