Pseudohexagonal 2D DNA Crystals from Double Crossover Cohesion

Two-dimensional pseudohexagonal trigonal arrays have been constructed by self-assembly from DNA. The motif used is a bulged-junction DNA triangle whose edges and extensions are DNA double crossover (DX) molecules, rather than conventional DNA double helices. Experiments were performed to establish whether the success of this system results from the added stiffness of DX molecules or the presence of two sticky ends at the terminus of each edge. Removal of one sticky end precludes lattice formation, suggesting that it is the double sticky end that is the primary factor enabling lattice formation

Shape-Controlled Nanofabrication of Conducting Polymer on Planar DNA Templates

Shape-Controlled Nanofabrication of Conducting Polymer on Planar DNA Template

Self-Assembled Catalytic DNA Nanostructures for Synthesis of Para-directed Polyaniline

Templated synthesis has been considered as an efficient approach to produce polyaniline (PANI) nanostructures. The features of DNA molecules enable a DNA template to be an intriguing template for fabrication of emeraldine PANI. In this work, we assembled HRP-mimicking DNAzyme with different artificial DNA nanostructures, aiming to manipulate the molecular structures and morphologies of PANI nanostructures through the controlled DNA self-assembly. UV–vis absorption spectra were used to investigate the molecular structures of PANI and monitor kinetic growth of PANI. It was found that PANI was well-doped at neutral pH and the redox behaviors of the resultant PANI were dependent on the charge density of the template, which was controlled by the template configurations. CD spectra indicated that the PANI threaded tightly around the helical DNA backbone, resulting in the right handedness of PANI. These reveal the formation of the emeraldine form of PANI that was doped by the DNA. The morphologies of the resultant PANI were studied by AFM and SEM. It was concluded from the imaging and spectroscopic kinetic results that PANI grew preferably from the DNAzyme sites and then expanded over the template to form 1D PANI nanostructures. The strategy of the DNAzyme-DNA template assembly brings several advantages in the synthesis of para-coupling PANI, including the region-selective growth of PANI, facilitating the formation of a para-coupling structure and facile regulation. We believe this study contributes significantly to the fabrication of doped PANI nanopatterns with controlled complexity, and the development of DNA nanotechnology

Plasmon–Exciton Strong Coupling Effects of the Chiral Hybrid Nanostructures Based on the Plexcitonic Born–Kuhn Model

A deep understanding of the optical properties of the chiral plexcitonic systems not only adds a new dimension to the exploration of the strong plasmon–exciton interaction but also provides a new method to design chiroptical devices. We develop a plexcitonic Born–Kuhn model to explore the strong coupling dynamics of the chiral hybrid nanostructures made of corner-stacked nanorod dimers and molecules from the chiroptical perspective. As a consequence of strong interaction between plasmons and excitons, double normal mode splittings/Rabi splittings and an anti-crossing phenomenon appear in circular dichroism (CD) spectroscopy. The character of dual plexciton (symmetric and anti-symmetric plexciton) and associated chiroptical properties have been demonstrated. The interplay between mirror symmetry breaking and plasmon–plasmon/plasmon–exciton interaction leads to an optimal configuration with the maximal chiroptical response. Moreover, chirality (of incident light) selective excitation of plexcitonic modes has been achieved by structural design. Finally, we verify our theory experimentally by synthesizing chiral plasmonic nanodimers and coating these structures with J-aggregate dye molecules

DNA-Based Nanotemplate Directed In Situ Synthesis of Silver Nanoclusters with Specific Fluorescent Emission: Surface-Guided Chemical Reactions

DNA-hosted silver nanoclusters (AgNCs) are a set of metallic fluorescent nanodots that possess high quantum yields and photostability. Here, we show the in situ hosted synthesis of AgNCs by single-stranded DNA preorganized on the self-assembled DNA nanostructure templates, which results in the site-specific formation of AgNCs with the specific fluorescence wavelengths. The excitation/emission properties of AgNCs were tuned by adjusting the distance between nucleation site and the template, the template configuration, and the location of the nucleation site on the template. Mass spectra analysis of AgNC products was performed to study the cluster sizes. The 5′ and 3′ ends of freely diffusing and template-supported host strands were labeled with a donor and an acceptor, and the FRET efficiency was evaluated to reveal the conformations of the host strands and their complexes with Ag⁺. It is indicated that the rigid template guided the synthetic pathway toward the preferential synthesis of AgNCs with a specific size distribution via a steric effect on the Ag⁺ adsorption to the host strands, which produces the specifically emissive AgNCs

Engineering Gold Nanoparticles with DNA Ligands for Selective Catalytic Oxidation of Chiral Substrates

Noble metal nanoparticles are promising materials for heterogeneous enantioselective catalysis because of their high surface-to-volume ratios, large concentrations of highly undercoordinated surface sites, and quantum confinement effects. In this work, we report on the use of DNA as an environment-responsive chiral ligand to engineer the selective catalytic behaviors of glucose oxidase-mimicking gold nanoparticles (AuNPs), with glucose enantiomers as the substrates. DNA can be stimulated externally to switch between random-coiled and multistranded structures (e.g., duplex, i-motif, or G-quadruplex). Random-coiled DNA-capped nanoparticles preferentially catalyze oxidation of l-glucose, and structured DNA-capped nanoparticles show higher activity toward d-glucose. pH-induced selectivity diminishment of DNA-treated AuNPs is also found, further demonstrating the chiral selector effect of DNA ligands. In the end, the selective catalysis of AuNPs allows control of the size enlargement of nanoparticles through self-catalytic Au⁰ deposition, in ligand- and substrate chirality-dependent manners. It is found that the effect of substrate chirality on the self-growth rate can be reversed by the hybridization of the capping DNA. The structural and chemical features of DNA grooves in the multistranded structures render binding sites with higher affinity to d-glucose than l-glucose. The results suggest a simple strategy for engineering the responsive enantioselective catalysis of metallic nanoparticles and advance the understanding of chiral interactions between nucleic acids and saccharide

Sheathless Focusing and Separation of Diverse Nanoparticles in Viscoelastic Solutions with Minimized Shear Thinning

Viscoelastic microfluidics becomes an efficient and label-free hydrodynamic technology to enrich and separate micrometer-scale particles, including blood cells, circulating tumor cells, and bacteria. However, the manipulation of nanoscale particles by viscoelastic microfluidics remains a major challenge, because the viscoelastic force acting on the smaller particle decreases dramatically. In contrast to the commonly used polymer solutions of high molecular weight, herein we utilize the aqueous solutions of poly­(ethylene oxide) (PEO) of low molecular weight with minimized shear thinning but sufficient elastic force for high-quality focusing and separation of various nanoparticles. The focusing efficiencies of 100 nm polystyrene (PS) nanoparticles and λ-DNA molecules are 84% and 85%, respectively, in a double spiral microchannel, without the aid of sheath flows. Furthermore, we demonstrate the size-based viscoelastic separation of two sets of binary mixtures100/2000 nm PS particles and λ-DNA molecules/blood plateletsall achieving separation efficiencies of >95% in the same device. Our proposal technique would be a promising approach for enrichment/separation of the nanoparticles encountered in applications of analytical chemistry and nanotechnology

Interconnecting Gold Islands with DNA Origami Nanotubes

Scaffolded DNA origami has recently emerged as a versatile, programmable method to fold DNA into arbitrarily shaped nanostructures that are spatially addressable, with sub-10-nm resolution. Toward functional DNA nanotechnology, one of the key challenges is to integrate the bottom-up self-assembly of DNA origami with the top-down lithographic methods used to generate surface patterning. In this report we demonstrate that fixed length DNA origami nanotubes, modified with multiple thiol groups near both ends, can be used to connect surface patterned gold islands (tens of nanometers in diameter) fabricated by electron beam lithography (EBL). Atomic force microscopic imaging verified that the DNA origami nanotubes can be efficiently aligned between gold islands with various interisland distances and relative locations. This development represents progress toward the goal of bridging bottom-up and top-down assembly approaches

Tumor-Targeted DNA Bipyramid for <i>in Vivo</i> Dual-Modality Imaging

A versatile DNA bipyramid nanostructure is assembled as a tumor-targeted, dual-modal nanoprobe for in vivo imaging. Magnetic resonance contrast agents (Gd-DOTA), fluorescence imaging molecules (Dylight800), and tumor-targeting moieties (anti-EGFR aptamers) were precisely organized on the DNA bipyramid platform. DNA bipyramids coated by polyethylene glycol-polylysine copolymer showed enhanced resistance against digestion in serum and prolonged circulation time in vivo. The multifunctional DNA bipyramid improved codelivery of magnetic resonance/fluorescence imaging (MR/FI) contrast agents to triple-negative breast tumors, realizing noninvasive tumor imaging without observable systemic toxicity. Our rationally designed DNA-based platform will prove powerful to develop customized molecular probes for cancer diagnosis

Gold Nanoparticle Self-Similar Chain Structure Organized by DNA Origami

Gold Nanoparticle Self-Similar Chain Structure Organized by DNA Origam