The emerging field of RNA nanotechnology

Abstract

Like DNA, RNA can be designed and manipulated to produce a variety of different nanostructures. Moreover, RNA has a flexible structure and possesses catalytic functions that are similar to proteins. Although RNA nanotechnology resembles DNA nanotechnology in many ways, the base-pairing rules for constructing nanoparticles are different. The large variety of loops and motifs found in RNA allows it to fold into numerous complicated structures, and this diversity provides a platform for identifying viable building blocks for various applications. The thermal stability of RNA also allows the production of multivalent nanostructures with defined stoichiometry. Here we review techniques for constructing RNA nanoparticles from different building blocks, we describe the distinct attributes of RNA inside the body, and discuss potential applications of RNA nanostructures in medicine. We also offer some perspectives on the yield and cost of RNA production.

Figure 1. Approaches in RNA Nanotechnology

The construction of RNA nanoparticles involves several steps: Following the conception, a computational approach can be applied to predict the folding and structure of the building blocks as well as the consequences of inter-RNA interactions in RNA nanoparticle assembly. After the synthesis of monomeric building blocks, the individual subunits can be further assembled into quaternary architectures utilizing the spontaneous self-folding property of RNA. The assembled RNA nanostructures will be characterized to ensure proper folding with desired structural/functional capabilities. After thorough evaluation, the nanoparticles will be then be used for various applications.

Figure 2. Comparison of self-assembled DNA (a,c,e,g), and RNA (b,d,f,h,I,j) nanoparticles

Images of DNA tiles (a)^, and RNA tiles via tectosquares (b); illustration of hexameric DNA gold nanoparticle (c)^,, pRNA hexameric ring (d)^,; DNA 3D polygons (e); and RNA cubic scaffolds (f) ^,; images of DNA bundles (g), RNA bundles (h), pRNA arrays (i); and 3D model of H-shaped tectoRNA (j). All images are taken by AFM except (g) and (j), as well as the first two images of (a), which are TEM images. All images were adapted from the individual references with permission.

Figure 3. Applications of RNA nanotechnology

Therapeutic nanoparticles harboring siRNA, ribozyme, aptamer, and other moieties are constructed using bacteriophage phi29 pRNA left- and right-hand interlocking loops or palindrome sequence without template^,,. Uppercase and lowercase letters signify right and left hand (a). Same letter pair, e.g., A–a′ indicates complementarity. Dimers assemble via pRNA A–b′ and B–a′ (b). Trimers form using pRNA A–b′, B–c′ and C–a′ (c). Foot-to-foot dimers form via end Palindrome sequence (d). Tetramers assemble by the combination of interlocking loops and palindrome mechanism (e). The right panel depicts AFM images adapted from ^, with permission.