Structural DNA nanotechnology: Immobile Holliday junctions to artificial robots

Abstreact: DNA nanotechnology marvels the scientific world with its capabilities to design, engineer, and demonstrate nanoscale shapes. This review is a condensed version walking the reader through the structural developments in the field over the past 40 years starting from the basic design rules of the double-stranded building block to the most recent advancements in self-assembled hierarchically achieved structures to date. It builds off from the fundamental motivation of building 3-dimensional (3D) lattice structures of tunable cavities going all the way up to artificial nanorobots fighting cancer. The review starts by covering the most important developments from the fundamental bottom-up approach of building structures, which is the ‘tile’ based approach covering 1D, 2D, and 3D building blocks, after which, the top-down approach using DNA origami and DNA bricks is also covered. Thereafter, DNA nanostructures assembled using not so commonly used (yet promising) techniques like i-motifs, quadruplexes, and kissing loops are covered. Highlights from the field of dynamic DNA nanostructures have been covered as well, walking the reader through the various approaches used within the field to achieve movement. The article finally concludes by giving the authors a view of what the future of the field might look like while suggesting in parallel new directions that fellow/future DNA nanotechnologists could think about.

Applications of DNA-Functionalized Proteins

As an important component that constitutes all the cells and tissues of the human body, protein is involved in most of the biological processes. Inspired by natural protein systems, considerable efforts covering many discipline fields were made to design artificial protein assemblies and put them into application in recent decades. The rapid development of structural DNA nanotechnology offers significant means for protein assemblies and promotes their application. Owing to the programmability, addressability and accurate recognition ability of DNA, many protein assemblies with unprecedented structures and improved functions have been successfully fabricated, consequently creating many brand-new researching fields. In this review, we briefly introduced the DNA-based protein assemblies, and highlighted the limitations in application process and corresponding strategies in four aspects, including biological catalysis, protein detection, biomedicine treatment and other applications.

Sequence Does Not Matter: The Biomedical Applications of DNA-Based Coatings and Cores

Biomedical applications of DNA are diverse but are usually associated with specific recognition of target nucleotide sequences or proteins and with gene delivery for therapeutic or biotechnological purposes. However, other aspects of DNA functionalities, like its nontoxicity, biodegradability, polyelectrolyte nature, stability, thermo-responsivity and charge transfer ability that are rather independent of its sequence, have recently become highly appreciated in material science and biomedicine. Whereas the latest achievements in structural DNA nanotechnology associated with DNA sequence recognition and Watson–Crick base pairing between complementary nucleotides are regularly reviewed, the recent uses of DNA as a raw material in biomedicine have not been summarized. This review paper describes the main biomedical applications of DNA that do not involve any synthesis or extraction of oligo- or polynucleotides with specified sequences. These sequence-independent applications currently include some types of drug delivery systems, biocompatible coatings, fire retardant and antimicrobial coatings and biosensors. The reinforcement of DNA properties by DNA complexation with nanoparticles is also described as a field of further research.

Targets and Tools: Nucleic Acids for Surface-Enhanced Raman Spectroscopy

Surface-enhanced Raman spectroscopy (SERS) merges nanotechnology with conventional Raman spectroscopy to produce an ultrasensitive and highly specific analytical tool that has been exploited as the optical signal read-out in a variety of advanced applications. In this feature article, we delineate the main features of the intertwined relationship between SERS and nucleic acids (NAs). In particular, we report representative examples of the implementation of SERS in biosensing platforms for NA detection, the integration of DNA as the biorecognition element onto plasmonic materials for SERS analysis of different classes of analytes (from metal ions to microorgniasms) and, finally, the use of structural DNA nanotechnology for the precise engineering of SERS-active nanomaterials.

Hybrid Nanoassemblies from Viruses and DNA Nanostructures

Viruses are among the most intriguing nanostructures found in nature. Their atomically precise shapes and unique biological properties, especially in protecting and transferring genetic information, have enabled a plethora of biomedical applications. On the other hand, structural DNA nanotechnology has recently emerged as a highly useful tool to create programmable nanoscale structures. They can be extended to user defined devices to exhibit a wide range of static, as well as dynamic functions. In this review, we feature the recent development of virus-DNA hybrid materials. Such structures exhibit the best features of both worlds by combining the biological properties of viruses with the highly controlled assembly properties of DNA. We present how the DNA shapes can act as “structured” genomic material and direct the formation of virus capsid proteins or be encapsulated inside symmetrical capsids. Tobacco mosaic virus-DNA hybrids are discussed as the examples of dynamic systems and directed formation of conjugates. Finally, we highlight virus-mimicking approaches based on lipid- and protein-coated DNA structures that may elicit enhanced stability, immunocompatibility and delivery properties. This development also paves the way for DNA-based vaccines as the programmable nano-objects can be used for controlling immune cell activation.

Strategies to Build Hybrid Protein–DNA Nanostructures

Proteins and DNA exhibit key physical chemical properties that make them advantageous for building nanostructures with outstanding features. Both DNA and protein nanotechnology have growth notably and proved to be fertile disciplines. The combination of both types of nanotechnologies is helpful to overcome the individual weaknesses and limitations of each one, paving the way for the continuing diversification of structural nanotechnologies. Recent studies have implemented a synergistic combination of both biomolecules to assemble unique and sophisticate protein–DNA nanostructures. These hybrid nanostructures are highly programmable and display remarkable features that create new opportunities to build on the nanoscale. This review focuses on the strategies deployed to create hybrid protein–DNA nanostructures. Here, we discuss strategies such as polymerization, spatial directing and organizing, coating, and rigidizing or folding DNA into particular shapes or moving parts. The enrichment of structural DNA nanotechnology by incorporating protein nanotechnology has been clearly demonstrated and still shows a large potential to create useful and advanced materials with cell-like properties or dynamic systems. It can be expected that structural protein–DNA nanotechnology will open new avenues in the fabrication of nanoassemblies with unique functional applications and enrich the toolbox of bionanotechnology.

Generating DNA Origami Nanostructures through Shape Annealing

Structural DNA nanotechnology involves the design and self-assembly of DNA-based nanostructures. As a field, it has progressed at an exponential rate over recent years. The demand for unique DNA origami nanostructures has driven the development of design tools, but current CAD tools for structural DNA nanotechnology are limited by requiring users to fully conceptualize a design for implementation. This article introduces a novel formal approach for routing the single-stranded scaffold DNA that defines the shape of DNA origami nanostructures. This approach for automated scaffold routing broadens the design space and generates complex multilayer DNA origami designs in an optimally driven way, based on a set of constraints and desired features. This technique computes unique designs of DNA origami assemblies by utilizing shape annealing, which is an integration of shape grammars and the simulated annealing algorithm. The results presented in this article illustrate the potential of the technique to code desired features into DNA nanostructures.

3D DNA Nanostructures: The Nanoscale Architect

Structural DNA nanotechnology is a pioneering biotechnology that presents the opportunity to engineer DNA-based hardware that will mediate a profound interface to the nanoscale. To date, an enormous library of shaped 3D DNA nanostructures have been designed and assembled. Moreover, recent research has demonstrated DNA nanostructures that are not only static but can exhibit specific dynamic motion. DNA nanostructures have thus garnered significant research interest as a template for pursuing shape and motion-dependent nanoscale phenomena. Potential applications have been explored in many interdisciplinary areas spanning medicine, biosensing, nanofabrication, plasmonics, single-molecule chemistry, and facilitating biophysical studies. In this review, we begin with a brief overview of general and versatile design techniques for 3D DNA nanostructures as well as some techniques and studies that have focused on improving the stability of DNA nanostructures in diverse environments, which is pivotal for its reliable utilization in downstream applications. Our main focus will be to compile a wide body of existing research on applications of 3D DNA nanostructures that demonstrably rely on the versatility of their mechanical design. Furthermore, we frame reviewed applications into three primary categories, namely encapsulation, surface templating, and nanomechanics, that we propose to be archetypal shape- or motion-related functions of DNA nanostructures found in nanoscience applications. Our intent is to identify core concepts that may define and motivate specific directions of progress in this field as we conclude the review with some perspectives on the future.

Strategies to Build Hybrid Protein-DNA Nanostructures

Proteins and DNA exhibit key physical chemical properties that make them advantageous for building nanostructures with outstanding features. Both DNA and protein nanotechnology have growth notably and proved to be fertile disciplines. The combination of both types of nanotechnologies is helpful to overcome the individual weaknesses and limitations of each one, paving the way for the continuing diversification of the structural nanotechnologies. Recent studies have implemented a synergistic combination of both biomolecules to assemble unique and sophisticate protein-DNA nanostructures. These hybrid nanostructures are highly programmable and display remarkable features that create new opportunities to build in the nanoscale. This review focuses on the strategies deployed to create hybrid protein-DNA nanostructures. Here, we will discuss strategies such as polymerization, spatial directing and organizing, coating, rigidizing or folding DNA into particular shapes or moving parts. The enrichment of structural DNA nanotechnology by incorporating protein nanotechnology has been clearly demonstrated and still shows a large potential to create useful and advanced materials with cell-like properties or dynamic systems. It can be expected that structural protein-DNA nanotechnology will open new avenues in the fabrication of nano-assemblies with unique functional applications and enrich the toolbox of bionanotechnology.