CONSPECTUS: In recent decades, DNA has taken on an assortment of diverse roles, not only as the central genetic molecule in biological systems but also as a generic material for nanoscale engineering. DNA possesses many exceptional properties, including its biological function, biocompatibility, molecular recognition ability, and nanoscale controllability. Taking advantage of these unique attributes, a variety of DNA materials have been created with properties derived both from the biological functions and from the structural characteristics of DNA molecules. These novel DNA materials provide a natural bridge between nanotechnology and biotechnology, leading to far-ranging real-world applications. In this Account, we describe our work on the design and construction of DNA materials. Based on the role of DNA in the construction, we categorize DNA materials into two classes: substrate and linker. As a substrate, DNA interfaces with enzymes in biochemical reactions, making use of molecular biology's "enzymatic toolkit". For example, employing DNA as a substrate, we utilized enzymatic ligation to prepare the first bulk hydrogel made entirely of DNA. Using this DNA hydrogel as a structural scaffold, we created a protein-producing DNA hydrogel via linking plasmid DNA onto the hydrogel matrix through enzymatic ligation. Furthermore, to fully make use of the advantages of both DNA materials and polymerase chain reaction (PCR), we prepared thermostable branched DNA that could remain intact even under denaturing conditions, allowing for their use as modular primers for PCR. Moreover, via enzymatic polymerization, we have recently constructed a physical DNA hydrogel with unique internal structure and mechanical properties. As a linker, we have used DNA to interface with other functional moieties, including gold nanoparticles, clay minerals, proteins, and lipids, allowing for hybrid materials with unique properties for desired applications. For example, we recently designed a DNA-protein conjugate as a universal adapter for protein detection. We further demonstrate a diverse assortment of applications for these DNA materials including diagnostics, protein production, controlled drug release systems, the exploration of life evolution, and plasmonics. Although DNA has shown great potential as both substrate and linker in the construction of DNA materials, it is still in the initial stages of becoming a well-established and widely used material. Important challenges include the ease of design and fabrication, scaling-up, and minimizing cost. We envision that DNA materials will continue to bridge the gap between nanotechnology and biotechnology and will ultimately be employed for many real-world applications.

A general methodology for the creation of arbitrary shapes and patterns is one of the ultimate goals of nanostructural studies. One approach to this goal is the formation of building blocks that cover nearly all varieties of shapes. Recently, DNA has become known as a new material for nanoscale structures. By using the Watson-Crick complementarity of the double helix, we can design 2D and 3D DNA nanostructures and self-assemble them in solution. The basic methodology of this structural DNA nanotechnology is to design a rigid motif that comprises several DNA junctions and can be used as a building block. Although the variety of motifs depends on the structural geometry of the junctions, almost all the structures reported to date have been based on a limited choice of crossover junctions. This restriction limits the available shapes of DNA nanostructures, which are mainly typified by parallel-packed duplexes. Herein, we report a novel interconnected single-duplex-based T-shaped junction and its use in the assembly of motifs, and therefore show how various structures can be designed and created without the use of conventional junctions. The use of these motifs overcomes the limitations in the varieties of available DNA nanostructures and provides a well-defined geometry for these structures. We show that motifs with T-shaped junctions are able to assemble into various structures in solution, such as orthogonal coordinated ladders, lattices, and polar coordinated wheels. Moreover, we also report that these structures can grow dramatically over the whole substrate surface in a new substrate-assisted assembly method.The invention of DNA double-crossover molecules [1] has allowed the creation of diverse DNA nanostructures, which gave rise to a new field in which DNA is used as a nanoscale building block. Immobilized stacked X formation of Holliday (crossover) junctions [4,5] was used to create a molecule with rigid parallel axes, thus defining a method to utilize the rigidity of DNA to form structures in solution. The formation of a rigid motif with several combined crossover junctions and subsequent connection of the junctions with single-

Ancient biomass is the main source for petrochemicals including plastics, which are inherently difficult to be degraded, increasingly polluting the earth's ecosystem including our oceans. To reduce the consumption by substituting or even replacing most of the petrochemicals with degradable and renewable materials is inevitable and urgent for a sustainable future. We report here a unique strategy to directly convert biomass DNA, at a large scale and with low cost, to diverse materials including gels, membranes, and plastics without breaking down DNA first into building blocks and without polymer syntheses. With excellent and sometimes unexpected, useful properties, we applied these biomass DNA materials for versatile applications for drug delivery, unusual adhesion, multifunctional composites, patterning, and everyday plastic objects. We also achieved cell-free protein production that had not been possible by petrochemical-based products. We expect our biomass DNA conversion approach to be adaptable to other biomass molecules including biomass proteins. We envision a promising and exciting era coming where biomass may replace petrochemicals for most if not all petro-based products.

Recent developments in nanotechnology have led to significant advancements in point-of-care (POC) nucleic acid detection. The ability to sense DNA and RNA in a portable format leads to important applications for a range of settings, from on-site detection in the field to bedside diagnostics, in both developing and developed countries. We review recent innovations in three key process components for nucleic acid detection: sample preparation, target amplification, and read-out modalities. We discuss how the advancements realized by nanotechnology are making POC nucleic acid detection increasingly applicable for decentralized and accessible testing, in particular for the developing world.

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Metabolism is a key process that makes life alive—the combination of anabolism and catabolism sustains life by a continuous flux of matter and energy. In other words, the materials comprising life are synthesized, assembled, dissipated, and decomposed autonomously in a controlled, hierarchical manner using biological processes. Although some biological approaches for creating dynamic materials have been reported, the construction of such materials by mimicking metabolism from scratch based on bioengineering has not yet been achieved. Various chemical approaches, especially dissipative assemblies, allow the construction of dynamic materials in a synthetic fashion, analogous to part of metabolism. Inspired by these approaches, here, we report a bottom-up construction of dynamic biomaterials powered by artificial metabolism, representing a combination of irreversible biosynthesis and dissipative assembly processes. An emergent locomotion behavior resembling a slime mold was programmed with this material by using an abstract design model similar to mechanical systems. Dynamic properties, such as autonomous pattern generation and continuous polarized regeneration, enabled locomotion along the designated tracks against a constant flow. Furthermore, an emergent racing behavior of two locomotive bodies was achieved by expanding the program. Other applications, including pathogen detection and hybrid nanomaterials, illustrated further potential use of this material. Dynamic biomaterials powered by artificial metabolism could provide a previously unexplored route to realize “artificial” biological systems with regenerating and self-sustaining characteristics.

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