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Circular RNAs (∼16−44 nt) were enzymatically synthesized efficientlyviaa novel DNA dumbbell splinting strategy, further, the circular 44 nt RNA was used as scaffold strands to construct hybrid and pure RNA double crossover tiles and nanostructures. 

In DNA nanotechnology, DNA molecules are designed, engineered, and assembled into arbitrary-shaped architectures with predesigned functions. Static DNA assemblies often have delicate designs with structural rigidity to overcome thermal fluctuations. Dynamic structures reconfigure in response to external cues, which have been explored to create functional nanodevices for environmental sensing and other applications. However, the precise control of reconfiguration dynamics has been a challenge due partly to flexible single-stranded DNA connections between moving parts. Deformable structures are special dynamic constructs with deformation on double-stranded parts and single-stranded hinges during transformation. These structures often have better control in programmed deformation. However, related deformability and mechanics including transformation mechanisms are not well understood or documented. In this review, we summarize the development of dynamic and deformable DNA nanostructures from a mechanical perspective. We present deformation mechanisms such as single-stranded DNA hinges with lock-and-release pairs, jack edges, helicity modulation, and external loading. Theoretical and computational models are discussed for understanding their associated deformations and mechanics. We elucidate the pros and cons of each model and recommend design processes based on the models. The design guidelines should be useful for those who have limited knowledge in mechanics as well as expert DNA designers. 

Surface-assisted, tile-based DNA self-assembly is a powerful method to construct large, two-dimensional (2D) nanoarrays. To further increase the structural complexity, one idea is to incorporate different types of tiles into one assembly system. However, different tiles have different adsorption strengths to the solid surface. The differential adsorptions make it difficult to control the effective molar ratio between different DNA tile concentrations on the solid surface, leading to assembly failure. Herein, we propose a solution to this problem by engineering the tiles with comparable molecular weights while maintaining their architectures. As a demonstration, we have applied this strategy to successfully assemble binary DNA 2D arrays out of very different tiles. We expect that this strategy would facilitate assembly of other complicated nanostructures as well.