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Mechanically interlocked DNA nanostructures for functional devices.

CONSPECTUS: Self-assembled functional DNA oligonucleotide based architectures represent highly promising candidates for the creation of nanoscale devices. The field of DNA nanotechnology has emerged to a high level of maturity and currently constitutes one of the most dynamic, creative, and exciting modern research areas. The transformation from structural DNA nanotechnology to functional DNA architectures is already taking place with tremendous pace. Particularly the advent of DNA origami technology has propelled DNA nanotechnology forward. DNA origami provided a versatile method for precisely aligning structural and functional DNA modules in two and three dimensions, thereby serving as a means for constructing scaffolds and chassis required for the precise orchestration of multiple functional DNA architectures. Key modules of these will contain interlocked nanomechanical components made of DNA. The mechanical interlocking allows for performing highly specific and controlled motion, by reducing the dimensionality of diffusion-controlled processes without restrictions in motional flexibility. Examples for nanoscale interlocked DNA architectures illustrate how elementary functional units of future nanomachines can be designed and realized, and show what role interlocked DNA architectures may play in this endeavor. Functional supramolecular systems, in general, and nanomachinery, in particular, self-organize into architectures that reflect different levels of complexity with respect to their function, their arrangement in the second and third dimension, their suitability for different purposes, and their functional interplay. Toward this goal, DNA nanotechnology and especially the DNA origami technology provide opportunities for nanomechanics, nanorobotics, and nanomachines. In this Account, we address approaches that apply to the construction of interlocked DNA nanostructures, drawing largely form our own contributions to interlocked architectures based on double-stranded (ds) circular geometries, and describe progress, opportunities, and challenges in rotaxanes and pseudorotaxanes made of dsDNA. Operating nanomechanical devices in a reliable and repetitive fashion requires methods for switching movable parts in DNA nanostructures from one state to another. An important issue is the orthogonality of switches that allow for operating different parts in parallel under spatiotemporal control. A variety of switching methods have been applied to switch individual components in interlocked DNA nanostructures like rotaxanes and catenanes. They are based on toehold, light, pseudocomplementary peptide nucleic acids (pcPNAs), and others. The key issues discussed here illustrate our perspective on the future prospects of interlocked DNA-based devices and the challenges that lay ahead.