Site-Specific Synthesis of Silica Nanostructures on DNA Origami Templates

DNA origami has been widely investigated as a template for the organization of various functional elements, leading to potential applications in many fields such as biosensing, nanoelectronics, and nanophotonics. However, the synthesis of inorganic nonmetallic nanomaterials with predesigned patterns using DNA origami templates has seldom been explored. Here, a novel method is reported to site-specifically synthesize silica nanostructures with designed patterns on DNA origami templates. The molecular dynamic simulation confirms that the positively charged silica precursors have a stronger electrostatic affinity to protruding double-stranded DNA (dsDNA) than DNA origami surfaces. The work describes a novel strategy to fabricate silica nanostructures with nanoscale precision. Moreover, the site-specific silicification of DNA nanoarchitectures expands the scope of customized synthesis of inorganic nonmetallic nanomaterials.     

Cryopreservation of DNA Origami Nanostructures

Although DNA origami nanostructures have found their way into numerous fields of fundamental and applied research, they often suffer from rather limited stability when subjected to environments that differ from the employed assembly conditions, that is, suspended in Mg²⁺‐containing buffer at moderate temperatures. Here, means for efficient cryopreservation of 2D and 3D DNA origami nanostructures and, in particular, the effect of repeated freezing and thawing cycles are investigated. It is found that, while the 2D DNA origami nanostructures maintain their structural integrity over at least 32 freeze–thaw cycles, ice crystal formation makes the DNA origami gradually more sensitive toward harsh sample treatment conditions. Whereas no freeze damage could be detected in 3D DNA origami nanostructures subjected to 32 freeze–thaw cycles, 1000 freeze–thaw cycles result in significant fragmentation. The cryoprotectants glycerol and trehalose are found to efficiently protect the DNA origami nanostructures against freeze damage at concentrations between 0.2 × 10^?3 and 200 × 10^?3 m and without any negative effects on DNA origami shape. This work thus provides a basis for the long‐term storage of DNA origami nanostructures, which is an important prerequisite for various technological and medical applications.     

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.     

DNA Mold-Based Fabrication of Palladium Nanostructures

DNA origami molds allow a shape-controlled growth of metallic nanoparticles. So far, this approach is limited to gold and silver. Here, the fabrication of linear palladium nanostructures with controlled lengths and patterns is demonstrated. To obtain nucleation centers for a seeded growth, a synthesis procedure of palladium nanoparticles (PdNPs) using Bis(p-sulfonatophenyl)phenylphosphine (BSPP) both as reductant and stabilizer is developed to establish an efficient functionalization protocol of the particles with single-stranded DNA. Attaching the functionalized particles to complementary DNA strands inside DNA mold cavities supports subsequently a highly specific seeded palladium deposition. This provides rod-like PdNPs with diameters of 20–35 nm of grainy morphology. Using an annealing procedure and a post-reduction step with hydrogen, homogeneous palladium nanostructures can be obtained. With the adaptation of the procedure to palladium the capabilities of the mold-based tool-box are expanded. In the future, this may allow a facile adaptation of the mold approach to less noble metals including magnetic materials such as Ni and Co.     

Self-Assembly of DNA Nanostructures in Different Cations

The programmable nature of DNA allows the construction of custom-designed static and dynamic nanostructures, and assembly conditions typically require high concentrations of magnesium ions that restricts their applications. In other solution conditions tested for DNA nanostructure assembly, only a limited set of divalent and monovalent ions are used so far (typically Mg²⁺ and Na⁺). Here, we investigate the assembly of DNA nanostructures in a wide variety of ions using nanostructures of different sizes: a double-crossover motif (76 bp), a three-point-star motif (~134 bp), a DNA tetrahedron (534 bp) and a DNA origami triangle (7221 bp). We show successful assembly of a majority of these structures in Ca²⁺, Ba²⁺, Na⁺, K⁺ and Li⁺ and provide quantified assembly yields using gel electrophoresis and visual confirmation of a DNA origami triangle using atomic force microscopy. We further show that structures assembled in monovalent ions (Na⁺, K⁺ and Li⁺) exhibit up to a 10-fold higher nuclease resistance compared to those assembled in divalent ions (Mg²⁺, Ca²⁺ and Ba²⁺). Our work presents new assembly conditions for a wide range of DNA nanostructures with enhanced biostability.     

固相萃取富集—高效液相色谱法分析水中多环芳烃(PAHs)

采用固相萃取与高效液相色谱联用技术,测定了水中的多环芳烃。实验中使用Supelco固相萃取过滤装置和Supelco C_(18)固相萃取小柱,100％的甲醇作为流动相。对于萤蒽(FLU),苯并(b)萤蒽(BbF),苯并(K)萤蒽(BkF),苯并(ghi)(BPer)及茚并(1,2,3-cd)芘(IP)的检测限分别为4.1,3.8,1.6,14.4,和3.8ng/L。     

DNA Nanostructures Carrying Stoichiometrically Definable Antibodies

Targeted drug delivery is one of the key challenges in cancer nanomedicine. Stoichiometric and spatial control over the antibodies placement on the nanomedicine vehicle holds a pivotal role to overcome this key challenge. Here, a DNA tetrahedral is designed with available conjugation sites on its vertices, allowing to bind one, two, or three cetuximab antibodies per DNA nanostructure. This stoichiometrically definable cetuximab conjugated DNA nanostructure shows enhanced targeting on the breast cancer cells, which results with higher overall killing efficacy of the cancer cells.     

Functional DNA Nanostructures for Photonic and Biomedical Applications

DNA nanostructures, especially DNA origami, receive close interest because of the programmable control over their shape and size, precise spatial addressability, easy and high‐yield preparation, mechanical flexibility, and biocompatibility. They have been used to organize a variety of nanoscale elements for specific functions, resulting in unprecedented improvements in the field of nanophotonics and nanomedical research. In this review, the discussion focuses on the employment of DNA nanostructures for the precise organization of noble metal nanoparticles to build interesting plasmonic nanoarchitectures, for the fabrication of visualized sensors and for targeted drug delivery. The effects offered by DNA nanostructures are highlighted in the areas of nanoantennas, collective plasmonic behaviors, single‐molecule analysis, and cancer‐cell targeting or killing. Finally, the challenges in the field of DNA nanotechnology for realistic application are discussed and insights for future directions are provided.     

Biomimetic and Bioinspired Synthesis of Nanomaterials/Nanostructures

In recent years, due to its unparalleled advantages, the biomimetic and bioinspired synthesis of nanomaterials/nanostructures has drawn increasing interest and attention. Generally, biomimetic synthesis can be conducted either by mimicking the functions of natural materials/structures or by mimicking the biological processes that organisms employ to produce substances or materials. Biomimetic synthesis is therefore divided here into “functional biomimetic synthesis” and “process biomimetic synthesis”. Process biomimetic synthesis is the focus of this review. First, the above two terms are defined and their relationship is discussed. Next different levels of biological processes that can be used for process biomimetic synthesis are compiled. Then the current progress of process biomimetic synthesis is systematically summarized and reviewed from the following five perspectives: i) elementary biomimetic system via biomass templates, ii) high‐level biomimetic system via soft/hard‐combined films, iii) intelligent biomimetic systems via liquid membranes, iv) living‐organism biomimetic systems, and v) macromolecular bioinspired systems. Moreover, for these five biomimetic systems, the synthesis procedures, basic principles, and relationships are discussed, and the challenges that are encountered and directions for further development are considered.     

微波辐照液相法合成石墨烯

以天然鳞片石墨为原料, 采用Hummers法先制备出石墨氧化物, 再采用微波辐照法在N-甲基吡咯烷酮(NMP)溶剂中合成出石墨烯. 微波辐照选择性地加热NMP溶剂, 同时石墨氧化物因其含氧官能团分解成CO、CO₂、H₂O气体而得以剥离和还原. 通过XRD、SEM、EDS、TEM、HRTEM、SAED、XPS和Raman测试手段对所合成的石墨烯进行了表征. 结果表明, 所合成的石墨烯尺寸为几微米, 呈透明绢丝状结构, 每个石墨烯片含有2~5层石墨层; 所合成的石墨烯可以均匀地分散在NMP溶剂中.     

准一维纳米材料制备方法的研究现状和发展趋势

本文介绍了准一维纳米结构所包含的一些基本概念以及在纳米科技中的重要地位.系统综述了近年来准一维纳米结构在制备方法方面的研究进展,并展望了其未来研究的发展方向.这对于目前准一维纳米结构的研究选题、方法借鉴都有重要的参考价值和指导意义.     

Distortion of DNA Origami on Graphene Imaged with Advanced TEM Techniques

While graphene may appear to be the ultimate support membrane for transmission electron microscopy (TEM) imaging of DNA nanostructures, very little is known if it poses an advantage over conventional carbon supports in terms of resolution and contrast. Microscopic investigations are carried out on DNA origami nanoplates that are supported onto freestanding graphene, using advanced TEM techniques, including a new dark‐field technique that is recently developed in our lab. TEM images of stained and unstained DNA origami are presented with high contrast on both graphene and amorphous carbon membranes. On graphene, the images of the origami plates show severe unwanted distortions, where the rectangular shape of the nanoplates is significantly distorted. From a number of comparative control experiments, it is demonstrated that neither staining agents, nor screening ions, nor the level of electron‐beam irradiation cause this distortion. Instead, it is suggested that origami nanoplates are distorted due to hydrophobic interaction of the DNA bases with graphene upon adsorption of the DNA origami nanoplates.     

Solution‐Controlled Conformational Switching of an Anchored Wireframe DNA Nanostructure

Self‐assembled DNA origami nanostructures have a high degree of programmable spatial control that enables nanoscale molecular manipulations. A surface‐tethered, flexible DNA nanomesh is reported herein which spontaneously undergoes sharp, dynamic conformational transitions under physiological conditions. The transitions occur between two major macrostates: a spread state dominated by the interaction between the DNA nanomesh and the BSA/streptavidin surface and a surface‐avoiding contracted state. Due to a slow rate of stochastic transition events on the order of tens of minutes, the dynamic conformations of individual structures can be detected in situ with DNA PAINT microscopy. Time series localization data with automated imaging processing to track the dynamically changing radial distribution of structural markers are combined. Conformational distributions of tethered structures in buffers with elevated pH exhibit a calcium‐dependent domination of the spread state. This is likely due to electrostatic interactions between the structures and immobilized surface proteins (BSA and streptavidin). An interaction is observed in solution under similar buffer conditions with dynamic light scattering. Exchanging between solutions that promote one or the other state leads to in situ sample‐wide transitions between the states. The technique herein can be a useful tool for dynamic control and observation of nanoscale interactions and spatial relationships.     

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。     

Daunorubicin‐Loaded DNA Origami Nanostructures Circumvent Drug‐Resistance Mechanisms in a Leukemia Model

Many cancers show primary or acquired drug resistance due to the overexpression of efflux pumps. A novel mechanism to circumvent this is to integrate drugs, such as anthracycline antibiotics, with nanoparticle delivery vehicles that can bypass intrinsic tumor drug‐resistance mechanisms. DNA nanoparticles serve as an efficient binding platform for intercalating drugs (e.g., anthracyclines doxorubicin and daunorubicin, which are widely used to treat acute leukemias) and enable precise structure design and chemical modifications, for example, for incorporating targeting capabilities. Here, DNA nanostructures are utilized to circumvent daunorubicin drug resistance at clinically relevant doses in a leukemia cell line model. The fabrication of a rod‐like DNA origami drug carrier is reported that can be controllably loaded with daunorubicin. It is further directly verified that nanostructure‐mediated daunorubicin delivery leads to increased drug entry and retention in cells relative to free daunorubicin at equal concentrations, which yields significantly enhanced drug efficacy. Our results indicate that DNA origami nanostructures can circumvent efflux‐pump‐mediated drug resistance in leukemia cells at clinically relevant drug concentrations and provide a robust DNA nanostructure design that could be implemented in a wide range of cellular applications due to its remarkably fast self‐assembly (≈5 min) and excellent stability in cell culture conditions.     

固相萃取-高效液相色谱法测定地表水中邻苯二甲酸酯

建立了固相萃取-高效液相色谱法分析8种邻苯二甲酸酯类物质,并对实际水样进行了测定。8种邻苯二甲酸酯类化合物的线性回归相关系数均大于0.999,检出限为0.11-0.19μg/L,保留时间和峰面积相对标准偏差分别为0.09-0.19%、0.25-0.56%,回收率为76.2-96.4%。