Beyond DNA origami: the unfolding prospects of nucleic acid nanotechnology

Chemical structures of nucleic acids. Nucleotide backbone structures for (a) DNA (left), RNA (right), (b) PNA, and (c) LNA. The right side of panel (a) also indicates the backbone hydrolysis reaction of RNA, where ‘AH⁺’ and ‘B’ are an acid and base catalyst, respectively. (d) Structure of a double‐stranded nucleic acid incorporating the four principal natural nucleobases A, T/U, G, and C, as well as the artificial P:Z base pair.

DNA crossover motifs. Examples for (a) double and (b) triple crossover motifs . The red strands show how the two and three helices, respectively, are linked.

The DNA origami method. (a) The single‐stranded DNA ‘scaffold’ strand (purple) is folded and held in place by specifically hybridizing ‘staple’ strands (red and green). (b) Resultant rectangular origami tile once all the staples have bound to the scaffold. (c) Triple crossover motifs demonstrated by the staples interacting with the scaffold. (d) 5′ ends of the staples are extended to create overhangs, which then can be decorated with partially complementary oligonucleotides (purple).

Current state‐of‐the‐art of nucleic‐acid‐based nanotechnology. (a) Molecular nanorobot walking along a track generated by decorating a rectangular origami with leg footholds (substrates); below, origami tile (boxed) imaged using AFM over time, indicating spider movement. (Reprinted with permission from Ref 47. Copyright 2010 Nature Publishing Group) (b) Multistep synthesis of an organic compound mediated by a deoxyribozyme. (Reprinted with permission from Ref 49. Copyright 2010 Nature Publishing Group) (c) Junctions of carbon nanotubes and origami to create a field‐effect transistor. (Reprinted with permission from Ref 50. Copyright 2010 Nature Publishing Group) (d) Transfer of photonic energy along a DNA template using FRET. (Reprinted with permission from Ref 55. Copyright 2010 American Chemical Society) (e) Triangular DNA origami arranged using electron‐beam lithography. (Reprinted with permission from Ref 56. Copyright 2010 Nature Publishing Group) (f) DNA nanotubes arranged using soft lithography. (Reprinted with permission from Ref 57. Copyright 2007 Wiley)

Hierarchy of areas impacted by DNA origami technology. The foundational DNA scaffolds (green) are used to create devices (blue) for a broad variety of applications (orange) that can be combined to enhance numerous emerging interdisciplinary fields (purple). Note that the nucleic acid nanotechnology field will not be limited by our current vision.

Progression in DNA and RNA nanotechnology. In nature, DNA forms structures such as the Holliday junction (field: DNA, Natural Past), which has inspired scientists to create more complex structures such as the rectangular DNA origami tile (DNA, Synthetic Present). In the future, such tiles may be used in fields including nanoelectronics as a scaffold for plasmonic circuit components to generate circuits that mimic neuron behavior (DNA, Combined Future). As the simple example in the figure depicts, a new circuit connection (purple) may be strengthened by repeated cooperative stimulation from excitatory pathways (green and blue) and hindered by the stimulation from an inhibitory pathway (orange). In nature, RNA plays a catalytic role in peptide bond formation by the ribosome, arguably the most important enzyme on earth (RNA, Natural Past). The catalytic and exquisite molecular recognition activity of RNA is exploited in (deoxy)ribozyme computing (RNA, Synthetic Present), which may be used in the future for complex therapeutic nanomedicine applications. For instance, a drug carrier, specifically delivered to a diseased cell through endocytosis triggered by binding to a protein on the cell surface, opens after entering the cell to release the drug (RNA, Combined Future). The contents of the drug carrier include a microRNA mimic that causes repression of a specific protein that otherwise would inhibit the surface marker, resulting in a cell that becomes more receptive to the drug carriers.