Folding DNA into a Lipid-Conjugated Nanobarrel for Controlled Reconstitution of Membrane Proteins

An Artificial Liposome Compartment with Size Exclusion Molecular Transport

The cellular compartment plays an essential role in organizing the complex and diverse biochemical reactions within the cell. By mimicking the function of such cellular compartments, the challenge of constructing artificial compartments has been taken up to develop new biochemical tools for efficient material production and diagnostics. The important features required for the artificial compartment are that it isolates the interior from the external environment and is further functionalized to control the transport of target chemicals to regulate the interior concentration of both substrate and reaction products. In this study, an artificial compartment with size-selective molecular transport function was constructed by using a DNA origami-guided liposome prepared by modifying the method reported by Perrault et al. This completely isolates the liposome interior, including the DNA origami skeleton, from the external environment and allows the assembly of a defined number of molecules of interest inside and/or outside the compartment. By incorporating a bacterial membrane protein, OmpF, into the liposome, the resulting artificial compartment was shown to transport only the molecule of interest with a molecular weight below 600 Da from the external environment into the interior of the compartment.

Functionalizing DNA origami to investigate and interact with biological systems

DNA origami has emerged as a powerful method to generate DNA nanostructures with dynamic properties and nanoscale control. These nanostructures enable complex biophysical studies and the fabrication of next-generation therapeutic devices. For these applications, DNA origami typically needs to be functionalized with bioactive ligands and biomacromolecular cargos. Here, we review methods developed to functionalize, purify, and characterize DNA origami nanostructures. We identify remaining challenges, such as limitations in functionalization efficiency and characterization. We then discuss where researchers can contribute to further advance the fabrication of functionalized DNA origami.

Pharmaceutical applications of framework nucleic acids

DNA is a biological polymer that encodes and stores genetic information in all living organism. Particularly, the precise nucleobase pairing inside DNA is exploited for the self-assembling of nanostructures with defined size, shape and functionality. These DNA nanostructures are known as framework nucleic acids (FNAs) for their skeleton-like features. Recently, FNAs have been explored in various fields ranging from physics, chemistry to biology. In this review, we mainly focus on the recent progress of FNAs in a pharmaceutical perspective. We summarize the advantages and applications of FNAs for drug discovery, drug delivery and drug analysis. We further discuss the drawbacks of FNAs and provide an outlook on the pharmaceutical research direction of FNAs in the future.

Obtaining Precise Molecular Information via DNA Nanotechnology

Precise characterization of biomolecular information such as molecular structures or intermolecular interactions provides essential mechanistic insights into the understanding of biochemical processes. As the resolution of imaging-based measurement techniques improves, so does the quantity of molecular information obtained using these methodologies. DNA (deoxyribonucleic acid) molecule have been used to build a variety of structures and dynamic devices on the nanoscale over the past 20 years, which has provided an accessible platform to manipulate molecules and resolve molecular information with unprecedented precision. In this review, we summarize recent progress related to obtaining precise molecular information using DNA nanotechnology. After a brief introduction to the development and features of structural and dynamic DNA nanotechnology, we outline some of the promising applications of DNA nanotechnology in structural biochemistry and in molecular biophysics. In particular, we highlight the use of DNA nanotechnology in determination of protein structures, protein-protein interactions, and molecular force.

Advancing Biophysics Using DNA Origami

DNA origami enables the bottom-up construction of chemically addressable, nanoscale objects with user-defined shapes and tailored functionalities. As such, not only can DNA origami objects be used to improve existing experimental methods in biophysics, but they also open up completely new avenues of exploration. In this review, we discuss basic biophysical concepts that are relevant for prospective DNA origami users. We summarize biochemical strategies for interfacing DNA origami with biomolecules of interest. We describe various applications of DNA origami, emphasizing the added value or new biophysical insights that can be generated: rulers and positioning devices, force measurement and force application devices, alignment supports for structural analysis for biomolecules in cryogenic electron microscopy and nuclear magnetic resonance, probes for manipulating and interacting with lipid membranes, and programmable nanopores. We conclude with some thoughts on so-far little explored opportunities for using DNA origami in more complex environments such as the cell or even organisms.

Revealing the structures of megadalton-scale DNA complexes with nucleotide resolution

The methods of DNA nanotechnology enable the rational design of custom shapes that self-assemble in solution from sets of DNA molecules. DNA origami, in which a long template DNA single strand is folded by many short DNA oligonucleotides, can be employed to make objects comprising hundreds of unique DNA strands and thousands of base pairs, thus in principle providing many degrees of freedom for modelling complex objects of defined 3D shapes and sizes. Here, we address the problem of accurate structural validation of DNA objects in solution with cryo-EM based methodologies. By taking into account structural fluctuations, we can determine structures with improved detail compared to previous work. To interpret the experimental cryo-EM maps, we present molecular-dynamics-based methods for building pseudo-atomic models in a semi-automated fashion. Among other features, our data allows discerning details such as helical grooves, single-strand versus double-strand crossovers, backbone phosphate positions, and single-strand breaks. Obtaining this higher level of detail is a step forward that now allows designers to inspect and refine their designs with base-pair level interventions.

Precision design of DNA origami needs precision validation. Here, the authors developed cryo-EM methods for obtaining high resolution structural data and for constructing pseudo-atomic models in a semi-automated fashion, allowing for iterative nanodevice inspection and refinement.

Programmable Nanodisc Patterning by DNA Origami

Nanodiscs (ND) are soluble phospholipid bilayers bounded by membrane scaffold proteins; they have become invaluable in the study of membrane proteins. However, this multifunctional tool has been used individually, and applications involving multiple NDs and their interactions have fallen far behind their counterpart membrane model system: liposomes. One major obstacle is the lack of reliable methods to manage the spatial arrangement of NDs. Here we sought to extend the utility of NDs by organizing them on DNA origami. NDs constructed with DNA-anchor amphiphiles were placed precisely and specifically into these DNA nanostructures via hybridization. Four different tethering strategies were explored and validated. A variety of geometric patterns of NDs were successfully programmed on origami, as evidenced by electron microscopy. The ND ensembles generated in this study provide new and powerful platforms to study protein-lipid or protein-protein interactions with spatial control of membranes.

Functional Applications of Nucleic Acid-Protein Hybrid Nanostructures

Combining the diverse chemical functionality of proteins with the predictable structural assembly of nucleic acids has enabled the creation of hybrid nanostructures for a range of biotechnology applications. Through the attachment of proteins onto or within nucleic acid nanostructures, materials with dynamic capabilities can be created that include switchable enzyme activity, targeted drug delivery, and multienzyme cascades for biocatalysis. Investigations of difficult-to-study biological mechanisms have also been aided by using DNA-protein assemblies that mimic natural processes in a controllable manner. Furthermore, advances that enable the recombinant production and intracellular assembly of hybrid nanostructures have the potential to overcome the significant manufacturing cost that has limited the use of DNA and RNA nanotechnology.

DNA Origami Post-Processing by CRISPR-Cas12a

Customizable nanostructures built through the DNA-origami technique hold tremendous promise in nanomaterial fabrication and biotechnology. Despite the cutting-edge tools for DNA-origami design and preparation, it remains challenging to separate structural components of an architecture built from-thus held together by-a continuous scaffold strand, which in turn limits the modularity and function of the DNA-origami devices. To address this challenge, here we present an enzymatic method to clean up and reconfigure DNA-origami structures. We target single-stranded (ss) regions of DNA-origami structures and remove them with CRISPR-Cas12a, a hyper-active ssDNA endonuclease without sequence specificity. We demonstrate the utility of this facile, selective post-processing method on DNA structures with various geometrical and mechanical properties, realizing intricate structures and structural transformations that were previously difficult to engineer. Given the biocompatibility of Cas12a-like enzymes, this versatile tool may be programmed in the future to operate functional nanodevices in cells.

Oligonucleotide-Polymer Conjugates: From Molecular Basics to Practical Application

DNA exhibits many attractive properties, such as programmability, precise self-assembly, sequence-coded biomedical functions, and good biocompatibility; therefore, DNA has been used extensively as a building block to construct novel nanomaterials. Recently, studies on oligonucleotide-polymer conjugates (OPCs) have attracted increasing attention. As hybrid molecules, OPCs exhibit novel properties, e.g., sophisticated self-assembly behaviors, which are distinct from the simple combination of the functions of DNA and polymer, making OPCs interesting and useful. The synthesis and applications of OPCs are highly dependent on the choice of the polymer block, but a systematic summary of OPCs based on their molecular structures is still lacking. In order to design OPCs for further applications, it is necessary to thoroughly understand the structure-function relationship of OPCs. In this review, we carefully categorize recently developed OPCs by the structures of the polymer blocks, and discuss the synthesis, purification, and applications for each category. Finally, we will comment on future prospects for OPCs.

Aptamer-Functionalized DNA Nanostructures for Biological Applications

DNA nanostructures hold great promise for various applications due to their remarkable properties, including programmable assembly, nanometric positional precision, and dynamic structural control. The past few decades have seen the development of various kinds of DNA nanostructures that can be employed as useful tools in fields such as chemistry, materials, biology, and medicine. Aptamers are short single-stranded nucleic acids that bind to specific targets with excellent selectivity and high affinity and play critical roles in molecular recognition. Recently, many attempts have been made to integrate aptamers with DNA nanostructures for a range of biological applications. This review starts with an introduction to the features of aptamer-functionalized DNA nanostructures. The discussion then focuses on recent progress (particularly during the last five years) in the applications of these nanostructures in areas such as biosensing, bioimaging, cancer therapy, and biophysics. Finally, challenges involved in the practical application of aptamer-functionalized DNA nanostructures are discussed, and perspectives on future directions for research into and applications of aptamer-functionalized DNA nanostructures are provided.

Bead-String-Shaped DNA Nanowires with Intrinsic Structural Advantages and Their Potential for Biomedical Applications

Due to high programmability and good biocompatibility, DNA has been recognized as a powerful building block for engineering of sophisticated nanostructures for different purposes. Herein, we present the first example of a bead-string-shaped DNA nanowire (BS-nanow) with long-range structural order for in vivo bioimaging and targeted drug delivery. BS-nanow is assembled from DNA tetrahedron units with precise nanometer-scale spatial control, capable of accommodating chemotherapeutic agents with high payload capacity (1204 binding sites) as well as possessing a 60-fold enhanced binding affinity for target cells. Confocal fluorescence imaging and in vivo experiments on CEM subcutaneous tumor-bearing mice show that specific bioimaging of living cells and even systemic delivery of drugs into internal tumor organs and tissues were accomplished, thereby achieving an efficient inhibition of tumor growth in the xenograft model without systemic toxicity. BS-nanow's show potential in vivo applications in accurate diagnosis and targeted therapy for human cancer.

Toward Precise Manipulation of DNA-Protein Hybrid Nanoarchitectures

Nucleic acids and proteins are the two primary building materials of living organisms. Over the past decade, artificial DNA-protein hybrid structures have been pursued for a wide range of applications. DNA nanotechnology, in particular, has dramatically expanded nanoscale molecule engineering and contributed to the spatial arrangement of protein components. Strategies for designing site-specific coupling of DNA oligomers to proteins are needed in order to allow for precise control over stoichiometry and position. Efforts have also been focused on coassembly of protein-DNA complexes by engineering their fundamental molecular recognition interactions. This Concept focuses on the precise manipulation of DNA-protein nanoarchitectures. Particular attention is paid to site-selectivity within DNA-protein conjugates, regulation of protein orientation using DNA scaffolds, and coassembly principles upon unique structural motifs. Current challenges and future directions are also discussed in the design and application of DNA-protein nanoarchitectures.

Emerging Biomimetic Applications of DNA Nanotechnology

Re-engineering cellular components and biological processes has received great interest and promised compelling advantages in applications ranging from basic cell biology to biomedicine. With the advent of DNA nanotechnology, the programmable self-assembly ability makes DNA an appealing candidate for rational design of artificial components with different structures and functions. This Forum Article summarizes recent developments of DNA nanotechnology in mimicking the structures and functions of existing cellular components. We highlight key successes in the achievements of DNA-based biomimetic membrane proteins and discuss the assembly behavior of these artificial proteins. Then, we focus on the construction of higher-order structures by DNA nanotechnology to recreate cell-like structures. Finally, we explore the current challenges and speculate on future directions of DNA nanotechnology in biomimetics.

Chemistries for DNA Nanotechnology

The predictable nature of DNA interactions enables the programmable assembly of highly advanced 2D and 3D DNA structures of nanoscale dimensions. The access to ever larger and more complex structures has been achieved through decades of work on developing structural design principles. Concurrently, an increased focus has emerged on the applications of DNA nanostructures. In its nature, DNA is chemically inert and nanostructures based on unmodified DNA mostly lack function. However, functionality can be obtained through chemical modification of DNA nanostructures and the opportunities are endless. In this review, we discuss methodology for chemical functionalization of DNA nanostructures and provide examples of how this is being used to create functional nanodevices and make DNA nanostructures more applicable. We aim to encourage researchers to adopt chemical modifications as part of their work in DNA nanotechnology and inspire chemists to address current challenges and opportunities within the field.

Recent advances in DNA nanotechnology

DNA is a powerful guiding molecule to achieve the precise construction of arbitrary structures and high-resolution organization of functional materials. The combination of sequence programmability, rigidity and highly specific molecular recognition in this molecule has resulted in a wide range of exquisitely designed DNA frameworks. To date, the impressive potential of DNA nanomaterials has been demonstrated from fundamental research to technological advancements in materials science and biomedicine. This review presents a summary of some of the most recent developments in structural DNA nanotechnology regarding new assembly approaches and efforts in translating DNA nanomaterials into practical use. Recent work on incorporating blunt-end stacking and hydrophobic interactions as orthogonal instruction rules in DNA assembly, and several emerging applications of DNA nanomaterials will also be highlighted.