Nucleic Acid Nanostructures for Chemical and Biological Sensing

The nanoscale features of DNA have made it a useful molecule for bottom‐up construction of nanomaterials, for example, two‐ and three‐dimensional lattices, nanomachines, and nanodevices. One of the emerging applications of such DNA‐based nanostructures is in chemical and biological sensing, where they have proven to be cost‐effective, sensitive and have shown promise as point‐of‐care diagnostic tools. DNA is an ideal molecule for sensing not only because of its specificity but also because it is robust and can function under a broad range of biologically relevant temperatures and conditions. DNA nanostructure‐based sensors provide biocompatibility and highly specific detection based on the molecular recognition properties of DNA. They can be used for the detection of single nucleotide polymorphism and to sense pH both in solution and in cells. They have also been used to detect clinically relevant tumor biomarkers. In this review, recent advances in DNA‐based biosensors for pH, nucleic acids, tumor biomarkers and cancer cell detection are introduced. Some challenges that lie ahead for such biosensors to effectively compete with established technologies are also discussed.     

An Acidic‐Microenvironment‐Driven DNA Nanomachine Enables Specific ATP Imaging in the Extracellular Milieu of Tumor

Extracellular ATP is an emerging target for cancer treatment because it is a key messenger for shaping the tumor microenvironment (TME) and regulating tumor progression. However, it remains a great challenge to design biochemical probes for targeted imaging of extracellular ATP in the TME. A TME‐driven DNA nanomachine (Apt‐LIP) that permits spatially controlled imaging of ATP in the extracellular milieu of tumors with ultrahigh signal‐to‐background ratio is reported. It operates in response to the mild acidity in the TME with the pH (low) insertion peptide (pHLIP) module, thus allowing the specific anchoring of the structure‐switching signaling aptamer unit to the membrane of tumor cells for “off–on” fluorescence imaging of the extracellular ATP. Apt‐LIP allows for acidity driven visualization of different extracellular concentrations of exogenous ATP, as well as the monitoring of endogenous ATP release from cells. Furthermore, it is demonstrated that Apt‐LIP represents a promising platform for the specific imaging of the extracellular ATP in both primary and metastatic tumors. Ultimately, since diverse aptamers are obtained through in vitro selection, this design strategy can be further applied for precise detection of various extracellular targets in the TME.     

Alignment and Graphene‐Assisted Decoration of Lyotropic Chromonic Liquid Crystals Containing DNA Origami Nanostructures

Composites of DNA origami nanostructures dispersed in a lyotropic chromonic liquid crystal are studied by polarizing optical microscopy. The homogeneous aqueous dispersions can be uniformly aligned by confinement between two glass substrates, either parallel to the substrates owing to uniaxial rubbing or perpendicular to the substrates using ozonized graphene layers. These opportunities of uniform alignment may pave the way for tailored anisometric plasmonic DNA nanostructures to photonic materials. In addition, a decorated texture with nonuniform orientation is observed on substrates coated with pristine graphene. When the water is allowed to evaporate slowly, microscopic crystal needles appear, which are aligned along the local orientation of the director. This decoration method can be used for studying the local orientational order and the defects in chromonic liquid crystals.     

A Light‐Driven Microgel Rotor

The current understanding of motility through body shape deformation of micro‐organisms and the knowledge of fluid flows at the microscale provides ample examples for mimicry and design of soft microrobots. In this work, a 2D spiral is presented that is capable of rotating by non‐reciprocal curling deformations. The body of the microswimmer is a ribbon consisting of a thermoresponsive hydrogel bilayer with embedded plasmonic gold nanorods. Such a system allows fast local photothermal heating and nonreciprocal bending deformation of the hydrogel bilayer under nonequilibrium conditions. It is shown that the spiral acts as a spring capable of large deformations thanks to its low stiffness, which is tunable by the swelling degree of the hydrogel and the temperature. Tethering the ribbon to a freely rotating microsphere enables rotational motion of the spiral by stroboscopic irradiation. The efficiency of the rotor is estimated using resistive force theory for Stokes flow. This research demonstrates microscopic locomotion by the shape change of a spiral and may find applications in the field of microfluidics, or soft microrobotics.     

A Molecular Hero Suit for In Vitro and In Vivo DNA Nanostructures

Precise control of DNA base pairing has rapidly developed into a field full of diverse nanoscale structures and devices that are capable of automation, performing molecular analyses, mimicking enzymatic cascades, biosensing, and delivering drugs. This DNA‐based platform has shown the potential of offering novel therapeutics and biomolecular analysis but will ultimately require clever modification to enrich or achieve the needed “properties” and make it whole. These modifications total what are categorized as the molecular hero suit of DNA nanotechnology. Like a hero, DNA nanostructures have the ability to put on a suit equipped with honing mechanisms, molecular flares, encapsulated cargoes, a protective body armor, and an evasive stealth mode.     

Coordination‐Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

2D materials have received tremendous scientific and engineering interests due to their remarkable properties and broad‐ranging applications such as energy storage and conversion, catalysis, biomedicine, electronics, and so forth. To further enhance their performance and endow them with new functions, 2D materials are proposed to hybridize with other nanostructured building blocks, resulting in hybrid nanostructures with various morphologies and structures. The properties and functions of these hybrid nanostructures depend strongly on the interfacial interactions between 2D materials and other building blocks. Covalent and coordination bonds are two strong interactions that hold high potential in constructing these robust hybrid nanostructures based on 2D materials. However, most 2D materials are chemically inert, posing problems for the covalent assembly with other building blocks. There are usually coordination atoms in most of 2D materials and their derivatives, thus coordination interaction as a strong interfacial interaction has attracted much attention. In this review, recent progress on the coordination‐driven hierarchical assembly based on 2D materials is summarized, focusing on the synthesis approaches, various architectures, and structure–property relationship. Furthermore, insights into the present challenges and future research directions are also presented.     

Stimuli‐Responsive Self‐Assembled DNA Nanomaterials for Biomedical Applications

Stimuli‐responsive DNA‐based materials represent a major class of remarkable functional nanomaterials for nano‐biotechnological applications. In this review, recent progress in the development of stimuli‐responsive systems based on self‐assembled DNA nanostructures is introduced and classified. Representative examples are presented in terms of their design, working principles and mechanisms to trigger the response of the stimuli‐responsive DNA system upon expose to a large variety of stimuli including pH, metal ions, oligonucleotides, small molecules, enzymes, heat, and light. Substantial in vitro studies have clearly revealed the advantages of the use of stimuli‐responsive DNA nanomaterials in different biomedical applications, particularly for biosensing, drug delivery, therapy and diagnostic purposes in addition to bio‐computing. Some of the challenges faced and suggestions for further development are also highlighted.     

DNA纳米结构在药物载体与控制释放中的应用

本文首先介绍了G四链体、双链结构、纳米管、折纸和立体笼状结构等DNA纳米结构用于药物载体时的载药特点;随后根据不同的刺激方式,从生物分子、pH、光和其他响应四个方面介绍了DNA纳米结构控制药物释放的途径及其利弊;进而对后续的研究提出了两点发展建议。     

Fluorescent Diarylethene Photoswitches—A Universal Tool for Super‐Resolution Microscopy in Nanostructured Materials

Super‐resolution fluorescence microscopy allows for unprecedented in situ visualization of biological structures, but its application to materials science has so far been comparatively limited. One of the main reasons is the lack of powerful dyes that allow for labeling and photoswitching in materials science systems. In this study it is shown that appropriate substitution of diarylethenes bearing a fluorescent closed and dark open form paves the way for imaging nanostructured materials with three of the most popular super‐resolution fluorescence microscopy methods that are based on different concepts to achieve imaging beyond the diffraction limit of light. The key to obtain optimal resolution lies in a proper control over the photochemistry of the photoswitches and its adaption to the system to be imaged. It is hoped that the present work will provide researchers with a guide to choose the best photoswitch derivative for super‐resolution microscopy in materials science, just like the correct choice of a Swiss Army Knife's tool is essential to fulfill a given task.