DNA-based switchable devices and materials

Abstract

Studies on DNA molecules have long been focused on its biological functions, since the discovery of the molecular structure of DNA by Watson and Crick [1] in 1953. DNA is known to be composed of adenine (A), guanine (G), cytosine (C) and thymine (T), and the Watson-Crick interaction of A-T and C-G base-pairing leads to the formation of the double-helix structure when sequences are complementary; this base-pairing process is also referred to as hybridization. Single-stranded DNA (ssDNA) is considered flexible, whereas double-stranded DNA (dsDNA) has a persistence length of about 50 nm. In the early 1980s [2], scientists started reconsidering the chemical composition of DNA, examining details such as chain structure, adjustable persistence length at the nanoscale, base-pair formation and programmable sequence. DNA quickly gained fresh recognition beyond strict biological roles and was rapidly introduced into the field of nanoscience as a new type of building block [3][4][5][6][7][8]. For example, DNA was used to fabricate nanostructures [9-14] from two-dimensional DNA nanostructures to three-dimensional curved nanostructures, as complex as spheres, ellipsoids, and flasks utilizing DNA origami techniques. DNA was also designed for the construction of molecular devices or machines that can generate nanoscale movement [15][16][17]. Besides static nanostructures, DNA could be applied to self-assembled structures [18,19] or integrated within other functional systems [20], utilizing properties of DNA such as specific recognition, chain-exchange reactions, specific enzyme reactions and secondary structure transformation to enable precise control of motion at the molecular level [19,21] or change properties at the macro scale [22]. Such responsive and switchable properties allow molecular machine-like devices to be built. [5,6] in the past several years. The present review focuses on DNA-based devices and smart materials that can respond to external stimuli, resulting in conformational changes to DNA structures at the nanoscale and detectable changes in properties such as volume, wettability at the macroscopic scale or transduction of force to move objects. This responsiveness is recoverable on removal of the external stimulus. DNA-based devices are introduced relating to smart surfaces and nanopores/nanochannels, while DNA-based smart materials are related to newly developed pure and hybrid DNA hydrogels. Figure 1 shows a typical example of a DNA device or motor. In 2003, Liu and Balasubramanian [19] proposed a pH-driven molecular motor system that is strong and swift. It comprises a 21mer ssDNA sequence X containing four stretches of three cytosines and a 17mer single-stranded DNA sequence Y, which is partially complementary to X. At pH 5, via the formation of C·CH+ base-pairs, sequence X folds into a compact 4-stranded i-motif structure with the 3' and 5' ends close to each other, representing the closed state of the motor. Changing the pH to 8 results in X unfolding and forming an extended DNA duplex structure XY, c...

Scaffolded biosensors with designed DNA nanostructures

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One-pot solvent exchange preparation of non-swellable, thermoplastic, stretchable and adhesive supramolecular hydrogels based on dual synergistic physical crosslinking

“…To improve the mechanical properties of chemically crosslinked hydrogels, researchers have developed ingenious strategies, including nanocomposite hydrogels, double-network hydrogels, hybrid crosslinking hydrogels and tetra-polyethylene glycol hydrogels. [14][15][16][17][18][19][20][21][22] Recently, increasing research attention has been dedicated to enhancing the mechanical performance of physically crosslinked supramolecular hydrogels. One recent study demonstrated very tough physical hydrogels composed of polyampholytes.…”

A DNA tweezer-actuated enzyme nanoreactor

“…Scientists are currently interested in finding ways to mimic enzyme regulatory circuitry outside of the cell 4,5 , not only to increase our knowledge of cellular metabolism but also so that we may create man-made nanoreactors that have potential utility in applications ranging from diagnostics to the production of high-value chemicals [6][7][8] and smart materials 9 . DNA nanostructures are promising scaffolds for use in the organization of molecules on the nanoscale because they can be engineered to site-specifically incorporate functional elements in precise geometries [10][11][12] and to enable nanomechanical control capabilities 13,14 . Examples of such structures include autonomous walkers 15,16 , nanotweezers [17][18][19][20] and nanocages for controlled encapsulation and payload release 21,22 .…”