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Chiral plasmonic nanostructures exhibit anomalously strong chiroptical signals and offer the possibility to realize asymmetric photophysical and photochemical processes controlled by circularly polarized light. Here, we use a chiral DNA-assembled nanorod pair as a model system for chiral plasmonic photomelting. We show that both the enantiomeric excess and consequent circular dichroism can be controlled with chiral light. The nonlinear chiroptical response of our plasmonic system results from the chiral photothermal effect leading to selective melting of the DNA linker strands. Our study describes both the single-complex and collective heating regimes, which should be treated with different models. The chiral asymmetry factors of the calculated photothermal and photomelting effects exceed the values typical for the chiral molecular photochemistry at least 10-fold. Our proposed mechanism can be used to develop chiral photoresponsive systems controllable with circularly polarized light.

The reliable programmability of DNA origami makes it an extremely attractive tool for bottom-up self-assembly of complex nanostructures. Utilizing this property for the tuned arrangement of plasmonic nanoparticles holds great promise particularly in the field of biosensing. Plasmonic particles are beneficial for sensing in multiple ways, from enhancing fluorescence to enabling a visualization of the nanoscale dynamic actuation via chiral rearrangements. In this Perspective, we discuss the recent developments and possible future directions of DNA origami-enabled plasmonic sensing systems. We start by discussing recent advancements in the area of fluorescence-based plasmonic sensing using DNA origami. We then move on to surface-enhanced Raman spectroscopy sensors followed by chiral sensing, both utilizing DNA origami nanostructures. We conclude by providing our own views on the future prospects for plasmonic biosensors enabled using DNA origami.

Over the past few decades, DNA has turned into one of the most widely used molecular linkers and a versatile building block for the self-assembly of DNA nanostructures. Such complexes, composed of only a few oligonucleotides (e.g., DNA tiles) or assembled from hundreds of synthetic and natural scaffolding strands (e.g., DNA origami), are being increasingly assembled into higher-order architectures such as lattices and crystals. A wide variety of assembly methods and techniques (e.g., solution-phase and substrate-assisted sticky-ended cohesion or blunt-end stacking) have emerged and are constantly being refined. This review provides a summary of the methods and building blocks for the assembly of 2D and 3D DNA lattices and crystals, and discusses some of their potential applications in materials science.

The design of dynamic, reconfigurable devices is crucial for the bottom-up construction of artificial biological systems. DNA can be used as an engineering material for the de-novo design of such dynamic devices. A self-assembled DNA origami switch is presented that uses the transition from double- to single-stranded DNA and vice versa to create and annihilate an entropic force that drives a reversible conformational change inside the switch. It is distinctively demonstrated that a DNA single-strand that is extended with 0.34 nm per nucleotide - the extension this very strand has in the double-stranded configuration - exerts a contractive force on its ends leading to large-scale motion. The operation of this type of switch is demonstrated via transmission electron microscopy, DNA-PAINT super-resolution microscopy and darkfield microscopy. The work illustrates the intricate and sometimes counter-intuitive forces that act in nanoscale physical systems that operate in fluids.

International audience; Synthetic biomimetic microswimmers are promising agents for in vivo healthcare and important frameworks to advance the understanding of locomotion strategies and collective motion at the microscopic scale. Nevertheless, constructing these devices with design flexibility and in large numbers remains a challenge. Here, a step toward meeting this challenge is taken by assembling such swimmers via the programmed shape and arrangement of superparamagnetic micromodules. The method's capacity for design flexibility is demonstrated through the assembly of a variety of swimmer architectures. On their actuation, strokes characterized by a balance of viscous and magnetic forces are found in all cases, but swimmers formed from a series of size‐graded triangular modules swim quicker than more traditional designs comprising a circular “head” and a slender tail. Linking performance to design, rules are extracted informing the construction of a second‐generation swimmer with a short tail and an elongated head optimized for speed. Its fast locomotion is attributed to a stroke that better breaks beating symmetry and an ability to beat fully with flex at high frequencies. Finally, production at scale is demonstrated through the assembly and swimming of a flock of the triangle‐based architectures to reveal four types of swimmer couplings.

The spatial organization of metal nanoparticles has become an important tool for manipulating light in nanophotonic applications. Silver nanoparticles, particularly silver nanorods, have excellent plasmonic properties but are prone to oxidation and are therefore inherently unstable in aqueous solutions and salt-containing buffers. Consequently, gold nanoparticles have often been favored, despite their inferior optical performance. Bimetallic, i.e., gold-silver core-shell nanoparticles, can resolve this issue. We present a method for synthesizing highly stable gold-silver core-shell NRs that are instantaneously functionalized with DNA, enabling chiral self-assembly on DNA origami. The silver shell gives rise to an enhancement of plasmonic properties, reflected here in strongly increased circular dichroism, as compared to pristine gold nanorods. Gold-silver nanorods are ideal candidates for plasmonic sensing with increased sensitivity as needed in pathogen RNA or antibody testing for nonlinear optics and light-funneling applications in surface enhanced Raman spectroscopy. Furthermore, the control of interparticle orientation enables the study of plasmonic phenomena, in particular, synergistic effects arising from plasmonic coupling of such bimetallic systems.

Improving the stability of DNA origami structures with respect to thermal, chemical, and mechanical demands will be essential to fully explore the real-life applicability of DNA nanotechnology. Here we present a strategy to increase the mechanical resilience of individual DNA origami objects and 3D DNA origami crystals in solution as well as in the dry state. By encapsulating DNA origami in a protective silica shell using sol-gel chemistry, all the objects maintain their structural integrity. This allowed for a detailed structural analysis of the crystals in a dry state, thereby revealing their true 3D shape without lattice deformation and drying-induced collapse. Analysis by energy-dispersive X-ray spectroscopy showed a uniform silica coating whose thickness could be controlled through the precursor concentrations and reaction time. This strategy thus facilitates shape-controlled bottom-up synthesis of designable biomimetic silica structures through transcription from DNA origami.

Precious metals and liquid crystals (LC) are quite different yet share some common features, for example, their beauty, distinguished optical properties and a competition of high prices per gramme. Triggered by the vision of artificial materials with extremely unusual properties (metamaterials), facilitated by the methods of modern nanotechnology and motivated by John Goodby’s and other colleagues’ synthetic activities, combinations of LCs and gold nanoparticles or nanostructures have attracted much attention during the last decade. This noncomprehensive article describes some examples and insights in this field. Perspectives and opportunities of further research are discussed.

International audience; Plasmonic materials are intensively used to extend the photoactivity of large bandgap semiconductors into the visible light region. In this framework, the present study examines the joint role played by the morphology and composition of plasmonic nano-particles in their photosensitizing capabilities. The critical influence of these parameters is evidenced by the effect of Au and core−shell Au@Ag nanorods on a TiO 2-driven photochemical probe reaction. In this case, the use of the bimetallic composites leads to a remarkable increase in the photocatalytic activity of the semiconductor compared to that found for the monometallic Au sensitizers. The mechanism behind this observation has then been computed theoretically concluding that, in terms of hot electron injection, the contribution of the transversal modes of the Au@Ag NRs and the low damping of these nanostructures are responsible for the photocatalytic properties reported herein. The great potential of these architectures is confirmed by their notable performance toward photocatalytic hydrogen generation, rendering this approach an appealing strategy in the search for efficient solar-driven energy systems. N oble metal nanoparticles (NPs) present outstanding optical properties given their strong interaction with light in the visible and near-infrared (NIR) ranges of the electromagnetic spectrum. 1 This coupling arises because of the coherent oscillation of conduction electrons of the metallic objects in resonance with the incoming electromagnetic field, an effect known as localized surface plasmon resonance (LSPR). 2 As a result, a short-lived population of charge carriers ("hot" electrons) is created, being thermalized within the crystalline lattice of the metal on the femtosecond time scale. 3,4 Recent reports have shown that the combination of plasmonic objects with acceptor species such as organic molecules or semiconductors can lead to the exchange of charge carriers and hence to the possibility of using such species to drive chemical processes of interest. 5 Along these lines, plasmonic photosensitization has been identified as a promising interaction between a noble metal and a large bandgap semiconductor toward the formation of hybrid photocatalysts with improved efficiencies and broadband activity. 6,7 In this manner, the Schottky barrier created between both materials extends the lifetime of the hot carriers, thus leading to an accumulation of electrons at the conduction band

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.

We demonstrate the capability of DNA selfassembledoptical antennas to direct the emission of anindividual fluorophore, which is free to rotate. DNA origami isused to fabricate optical antennas composed of two colloidalgold nanoparticles separated by a predefined gap and to place asingle Cy5 fluorophore near the gap center. Although thefluorophore is able to rotate, its excitation and far-field emissionis mediated by the antenna, with the emission directionalityfollowing a dipolar pattern according to the antenna mainresonant mode. This work is intended to set out the basis formanipulating the emission pattern of single molecules with selfassembledoptical antennas based on colloidal nanoparticles. Fil: Hübner, Kristina. Universidad de Múnich; Alemania Fil: Pilo-Pais, Mauricio. Fribourg University; Suiza Fil: Selbach, Florian. Universidad de Múnich; Alemania Fil: Liedl, Tim. Universidad de Múnich; Alemania Fil: Tinnefeld, Philip. Universidad de Múnich; Alemania Fil: Stefani, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina Fil: Acuna, Guillermo P.. Fribourg University; Suiza

DNA nanotechnology has developed into a state where the design and assembly of complex nanoscale structures has become fast, reliable, cost-effective, and accessible to non-experts. Nanometer-precise positioning of organic (dyes, biomolecules, etc.) and inorganic (metal nanoparticles, colloidal quantum dots, etc.) components on DNA nanostructures is straightforward and modular. In this perspective article, we identify the opportunities and challenges that DNA-assembled devices and materials are facing for optical antennas, metamaterials, and sensing applications. With the abilities of arranging hybrid materials in defined geometries, plasmonic effects will, for example, amplify molecular recognition transduction so that single-molecule events will be measureable with simple devices. On the larger scale, DNA nanotechnology has the potential of breaking the symmetry of common self-assembled functional materials creating pre-defined optical properties such as refractive index tuning, Bragg reflection and topological insulation.

Rod-like and sheet-like nano-particles made of desoxyribonucleic acid (DNA) fabricated by the DNA origami method (base sequence-controlled self-organized folding of DNA) are dispersed in a lyotropic chromonic liquid crystal made of an aqueous solution of disodium cromoglycate. The respective liquid crystalline nanodispersions are doped with a dichroic fluorescent dye and their orientational order parameter is studied by means of polarized fluorescence spectroscopy. The presence of the nano-particles is found to slightly reduce the orientational order parameter of the nematic mesophase. Nano-rods with a large length/width ratio tend to preserve the orientational order, while more compact stiff nano-rods and especially nano-sheets reduce the order parameter to a larger extent. In spite of the difference between the sizes of the DNA nano-particles and the rod-like columnar aggregates forming the liquid crystal, a similarity between the shapes of the former and the latter seems to be better compatible with the orientational order of the liquid crystal.

Owing to their unique optical properties, colloidal quantum dots (QDs) have attracted much attention as versatile fluorescent markers with broad biological and physical applications. On the other hand, DNA-based assembly has proven to be a powerful bottom-up approach to create designer nanoscale objects and to use these objects for the site-directed arrangement of guest components. To achieve good colloidal stability and accurate positioning of QDs on DNA templates, robust QD surface functionalization is crucial. Here, we present a simple and reliable conjugation method for the direct attachment of DNA molecules to QDs. Phosphorothiolated regions of chimera oligonucleotides are attached and incorporated into a ZnS layer freshly growing in situ on QDs that were rendered water soluble with hydrophilic ligands in a prior step. The reaction can be completed in a 2 mL plastic tube without any special equipment. The utility of these DNA-labeled QDs is demonstrated via prototypical assemblies such as QDs dimers with various spacings and chiral helical architectures.

DNA nanostructures offer the possibility to mimic functional biological membrane components due to their nanometer-precise shape configurability and versatile biochemical functionality. Here we show that the diffusional behavior of DNA nanostructures and their assembly into higher order membrane-bound lattices can be controlled in a stop-and-go manner and that the process can be monitored with super-resolution imaging. The DNA structures are transiently immobilized on glass-supported lipid bilayers by changing the mono- and divalent cation concentrations of the surrounding buffer. Using DNA points accumulation for imaging in nanoscale topography (DNA-PAINT) super-resolution microscopy, we confirm the fixation of DNA origami structures with different shapes. On mica-supported lipid bilayers, in contrast, we observe residual movement. By increasing the concentration of NaCl and depleting MgCl2, a large fraction of DNA structures restarts to diffuse freely on both substrates. After addition of a set of oligonucleotides that enables three Y-shaped monomers to assemble into a three-legged shape (triskelion), the triskelions can be stopped and super-resolved. Exchanging buffer and adding another set of oligonucleotides triggers the triskelions to diffuse and assemble into hexagonal 2D lattices. This stop-and-go imaging technique provides a way to control and observe the diffusional behavior of DNA nanostructures on lipid membranes that could also lead to control of membrane-associated cargos.

The use of biomaterials, with techniques such as DNA-directed assembly or biodirected synthesis, can surpass top-down fabrication techniques in creating plasmonic superstructures in terms of spatial resolution, range of functionality, and fabrication speed. In particular, by enabling a very precise placement of nanoparticles in a bioassembled complex or through the controlled biodirected shaping of single nanoparticles, plasmonic nanocrystals can show remarkably strong circular dichroism (CD) signals. We show that chiral bioplasmonic assemblies and single nanocrystals can enable polarization-sensitive photochemistry based on the generation of energetic (hot) electrons. It is now established that hot plasmonic electrons can induce surface photochemistry or even reshape plasmonic nanocrystals. We show that merging chiral plasmonic nanocrystal systems and the hot-election generation effect offers unique possibilities in photochemistry, such as polarization-sensitive photochemistry promoting nonchiral molecular reactions, chiral photoinduced growth of a colloid at the atomic level, and chiral photochemical destruction of chiral nanocrystals. In contrast, for chiral molecular systems, the equivalent of the described effects is challenging to observe because molecular species typically exhibit very small CD signals. Moreover, we compare our findings with traditional chiral photochemistry at the molecular level, identifying new, different regimes for chiral photochemistry with possibilities that are unique for plasmonic colloidal systems. In this study, we bring together the concept of hot-electron generation and the field of chiral colloidal plasmonics. Using chiral plasmonic nanorod complexes as a model system, we demonstrate remarkably strong CD in both optical extinction and generation rates of hot electrons. Studying the regime of steady-state excitation, we discuss the influence of geometrical and material parameters on the chiral effects involved in the generation of hot electrons. Optical chirality and the chiral hot-electron response in the nanorod dimers result from complex interparticle interactions, which can appear in the weak coupling regime or in the form of Rabi splitting. Regarding practical applications, our study suggests interesting opportunities in polarization-sensitive photochemistry, in chiral recognition or separation, and in promoting chiral crystal growth at the nanoscale.

The chiral state of a molecule plays a crucial role in molecular recognition and biochemical reactions. Because of this and owing to the fact that most modern drugs are chiral, the sensitive and reliable detection of the chirality of molecules is of great interest to drug development. The majority of naturally occurring biomolecules exhibit circular dichroism (CD) in the UV range. Theoretical studies and several experiments have demonstrated that this UV-CD can be transferred into the plasmonic frequency domain when metal surfaces and chiral biomolecules are in close proximity. Here, we demonstrate that the CD transfer effect can be drastically enhanced by placing chiral molecules, here double-stranded DNA, inside a plasmonic hotspot. By using different particle types (gold, silver, spheres, and rods) and by exploiting the versatility of DNA origami, we were able to systematically study the impact of varying particle distances on the CD transfer efficiency and to demonstrate CD transfer over the whole optical spectrum down to the near-infrared. For this purpose, nanorods were also placed upright on DNA origami sheets, forming strong optical antennas. Theoretical models, demonstrating the intricate relationships between molecular chirality and achiral electric fields, support our experimental findings. From both experimental measurements and theoretical considerations, we conclude that the transferred CD is most intensive for systems with strong plasmonic hotspots, as we find them in relatively small gaps (5-12 nm) between spherical nanoparticles and preferably between the tips of nanorods.

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.

We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria. Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials.

DNA origami objects allow for accurate positioning of guest molecules in three dimensions. Validation and understanding of design strategies for particle attachment as well as analysis of specific particle arrangements are desirable. Small-angle X-ray scattering (SAXS) is suited to probe distances of nano-objects with subnanometer resolution at physiologically relevant conditions including pH and salt and at varying temperatures. Here, we show that the pair density distribution function (PDDF) obtained from an indirect Fourier transform of SAXS intensities in a model-free way allows to investigate prototypical DNA origami-mediated gold nanoparticle (AuNP) assemblies. We analyze the structure of three AuNP-dimers on a DNA origami block, an AuNP trimer constituted by those dimers, and a helical arrangement of nine AuNPs on a DNA origami cylinder. For the dimers, we compare the model-free PDDF and explicit modeling of the SAXS intensity data by superposition of scattering intensities of the scattering objects. The PDDF of the trimer is verified to be a superposition of its dimeric contributions, that is, here AuNP-DNA origami assemblies were used as test boards underlining the validity of the PDDF analysis beyond pairs of AuNPs. We obtain information about AuNP distances with an uncertainty margin of 1.2 nm. This readout accuracy in turn can be used for high precision placement of AuNP by careful design of the AuNP attachment sites on the DNA-structure and by fine-tuning of the connector types.

The mechanical properties of DNA nanostructures are of widespread interest as applications that exploit their stability under constant or intermittent external forces become increasingly common. We explore the force response of DNA origami in comprehensive detail by combining AFM single molecule force spectroscopy experiments with simulations using oxDNA, a coarse-grained model of DNA at the nucleotide level, to study the unravelling of an iconic origami system: the Rothemund tile. We contrast the force-induced melting of the tile with simulations of an origami 10-helix bundle. Finally, we simulate a recently proposed origami biosensor, whose function takes advantage of origami behavior under tension. We observe characteristic stick-slip unfolding dynamics in our force-extension curves for both the Rothemund tile and the helix bundle and reasonable agreement with experimentally observed rupture forces for these systems. Our results highlight the effect of design on force response: we observe regular, modular unfolding for the Rothemund tile that contrasts with strain-softening of the 10-helix bundle which leads to catastropic failure under monotonically increasing force. Further, unravelling occurs straightforwardly from the scaffold ends inward for the Rothemund tile, while the helix bundle unfolds more nonlinearly. The detailed visualization of the yielding events provided by simulation allows preferred pathways through the complex unfolding free-energy landscape to be mapped, as a key factor in determining relative barrier heights is the extensional release per base pair broken. We shed light on two important questions: how stable DNA nanostructures are under external forces and what design principles can be applied to enhance stability.

Metallic nanostructures can be used to manipulate light on the subwavelength scale to create tailored optical material properties. Next to electric responses, artificial optical magnetism is of particular interest but difficult to achieve at visible wavelengths. DNA-self-assembly has proved to serve as a viable method to template plasmonic materials with nanometer precision and to produce large quantities of metallic objects with high yields. We present here the fabrication of self-assembled ring-shaped plasmonic metamolecules that are composed of four to eight single metal nanoparticles with full stoichiometric and geometric control. Scattering spectra of single rings as well as absorption spectra of solutions containing the metamolecules are used to examine the unique plasmonic features, which are compared to computational simulations. We demonstrate that the electric and magnetic plasmon resonance modes strongly correlate with the exact shape of the structures. In particular, our computations reveal the magnetic plasmons only for particle rings of broken symmetries, which is consistent with our experimental data. We stress the feasibility of DNA self-assembly as a method to create bulk plasmonic materials and metamolecules that may be applied as building blocks in plasmonic devices.

We measure the stiffness of tiled DNA nanotubes (HX-tubes) as a function of their (defined) circumference by analyzing their micrometer-scale thermal deformations using fluorescence microscopy. We derive a model that relates nanoscale features of HX-tube architecture to the measured persistence lengths. Given the known stiffness of double-stranded DNA, we use this model to constrain the average spacing between and effective stiffness of individual DNA duplexes in the tube. A key structural feature of tiled nanotubes that can affect stiffness is their potential to form with discrete amounts of twist of the DNA duplexes about the tube axis (supertwist). We visualize the supertwist of HX-tubes using electron microscopy of gold nanoparticles, attached to specific sites along the nanotube. This method reveals that HX-tubes tend not to form with supertwist unless forced by sequence design, and, even when forced, supertwist is reduced by elastic deformations of the underlying DNA lattice. We compare the hybridization energy gained upon closing a duplex sheet into a tube with the elastic energy paid for deforming the sheet to allow closure. In estimating the elastic energy we account for bending and twisting of the individual duplexes as well as shearing between them. We find the minimum supertwist state has minimum free energy, and global untwisting of forced supertwist is energetically favorable, consistent with our experimental data. Finally, we show that attachment of Cy3 dyes or changing counterions can cause nanotubes to adopt a permanent writhe with micrometer-scale pitch and amplitude. We propose that the coupling of local twist and global counter-twist may be useful in characterizing perturbations of DNA structure.

Multihelical DNA bundles could enhance the functionality of nanomaterials and serve as model architectures to mimic protein filaments on the molecular and cellular level. We report the self-assembly of micrometer-sized helical DNA nanotubes with widely controllable helical diameters ranging from tens of nanometers to a few micrometers. Nanoscale helical shapes of DNA tile tubes (4-, 6-, 8-, 10-, and 12-helix tile tubes) are achieved by introducing discrete amounts of bending and twist through base pair insertions and/or deletions. Microscale helical diameters, which require smaller amounts of twist and bending, are achieved by controlling the intrinsic “supertwist” present in tile tubes with uneven number of helices (11-, 13-, and 15-helix tile tubes). Supertwist fine-tuning also allows us to produce helical nanotubes of defined chirality.

The biopolymer DNA allows to create nanoscale, biocompatible structures, which can be designed in a target-specific and stimuli-responsive manner. DNA carrier systems with these characteristics hold a great potential for nanomedical applications, such as for the treatment of inflammatory diseases. Here we used a DNA-based drug carrier system for the pH-dependent delivery of the glucocorticoid dexamethasone into macrophages, a cell type with a key role in the regulation of inflammation. Dexamethasone (Dex) nanotubes were internalized within minutes by MH-S macrophages in vitro and by tissue resident macrophages in the mouse cremaster muscle in vivo and localized in their endosomes. Treatment with Dex nanotubes in vitro significantly reduced the LPS-induced TNF secretion by macrophages, as compared to equivalent amounts of free dexamethasone without affecting cell viability. Microinjection of Dex nanotubes into postischemic muscle tissue of anesthetized mice resulted in a marked reduction of ischemia-reperfusion-elicited leukocyte transmigration and diminished vascular expression of the endothelial adhesion molecules VCAM-1 and ICAM-1. Taken together, our results demonstrate that DNA nanotubes can be used as a platform for the targeted delivery of glucocorticoids and could thus foster the development of nanomedical therapeutics with reduced off-target effects.

The self-assembly of nanoscale elements into three-dimensional structures with precise shapes and sizes is important in fields such as nanophotonics, metamaterials and biotechnology. Short molecular linkers have previously been used to create assemblies of nanoparticles, but the approach is limited to small interparticle distances, typically less than 10 nm. Alternatively, DNA origami can precisely organize nanoscale objects over much larger length scales. Here we show that rigid DNA origami scaffolds can be used to assemble metal nanoparticles, quantum dots and organic dyes into hierarchical nanoclusters that have a planet-satellite-type structure. The nanoclusters have a tunable stoichiometry, defined distances of 5-200 nm between components, and controllable overall sizes of up to 500 nm. We also show that the nanoscale components can be positioned along the radial DNA spacers of the nanostructures, which allows short- and long-range interactions between nanoparticles and dyes to be studied in solution. The approach could, in the future, be used to construct efficient energy funnels, complex plasmonic architectures, and porous, nanoengineered scaffolds for catalysis.

We study the distance-dependent quenching of fluorescence due to a metallic nanoparticle in proximity of a fluorophore. In our single-molecule measurements, we achieve excellent control over structure and stoichiometry by using self-assembled DNA structures (DNA origami) as a breadboard where both the fluorophore and the 10 nm metallic nanoparticle are positioned with nanometer precision. The single-molecule spectroscopy method employed here reports on the co-localization of particle and dye, while fluorescence lifetime imaging is used to directly obtain the correlation of intensity and fluorescence lifetime for varying particle to dye distances. Our data can be well explained by exact calculations that include dipole dipole orientation and distances. Fitting with a more practical model for nanosurface energy transfer yields 10.4 nm as the characteristic distance of 50% energy transfer. The use of DNA nanotechnology together with minimal sample usage by attaching the particles to the DNA origami directly on the microscope coverslip paves the way for more complex experiments exploiting dye nanoparticle interactions. Fil: Acuna, Guillermo P.. Technische Universität Braunschweig; Alemania Fil: Bucher, Martina. Ludwig Maximilians Universitat; Alemania Fil: Stein, Ingo H.. Ludwig Maximilians Universitat; Alemania Fil: Steinhauer, Christian. Ludwig Maximilians Universitat; Alemania Fil: Kuzyk, Anton. Technische Universitat Munchen; Alemania Fil: Holzmeister, Phil. Technische Universität Braunschweig; Alemania Fil: Schreiber, Robert. Ludwig Maximilians Universitat; Alemania Fil: Moroz, Alexander. Fil: Stefani, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Liedl, Tim. Ludwig Maximilians Universitat; Alemania Fil: Simmel, Friedrich C.. Technische Universitat Munchen; Alemania Fil: Tinnefeld, Philip. Technische Universität Braunschweig; Alemania

We demonstrate the assembly of functional hybrid nanopores for single molecule sensing by inserting DNA origami structures into solid-state nanopores. In our experiments, single artificial nanopores based on DNA origami are repeatedly inserted in and ejected from solid-state nanopores with diameters around 15 nm. We show that these hybrid nanopores can be employed for the detection of λ-DNA molecules. Our approach paves the way for future development of adaptable single-molecule nanopore sensors based on the combination of solid-state nanopores and DNA self-assembly.

The application of three-dimensional DNA origami objects as rigid mechanical mediators or force sensing elements requires detailed knowledge about their complex mechanical properties. Using magnetic tweezers, we directly measure the bending and torsional rigidities of four- and six-helix bundles assembled by this technique. Compared to duplex DNA, we find the bending rigidities to be greatly increased while the torsional rigidities are only moderately augmented. We present a mechanical model explicitly including the crossovers between the individual helices in the origami structure that reproduces the experimentally observed behavior. Our results provide an important basis for the future application of 3D DNA origami in nanomechanics.

DNA self‐assembly is a powerful tool to arrange optically active components with high accuracy in a large parallel manner. A facile approach to assemble plasmonic antennas consisting of two metallic nanoparticles (40 nm) with a single colloidal quantum dot positioned at the hot spot is presented here. The design approach is based on DNA complementarity, stoichiometry, and steric hindrance principles. Since no intermediate molecules other than short DNA strands are required, the structures possess a very small gap (≈ 5 nm) which is desired to achieve high Purcell factors and plasmonic enhancement. As a proof‐of‐concept, the fluorescence emission from antennas assembled with both conventional and ultrasmooth spherical gold particles is measured. An increase in fluorescence is obtained, up to ≈30‐fold, compared to quantum dots without antenna.

Tensegrity or tensional integrity is a property of a structure that relies on a balance between components that are either in pure compression or in pure tension for its stability [1,2]. Tensegrity structures exhibit extremely high strength-to-weight ratios and great resilience, and are therefore widely used in engineering, robotics and architecture [3,4]. Here we report nanoscale, prestressed, three-dimensional tensegrity structures in which rigid bundles of DNA double helices resist compressive forces exerted by segments of single-stranded DNA that act as tension-bearing cables. Our DNA tensegrity structures can self-assemble against forces up to 14 pN, which is twice the stall force of powerful molecular motors such as kinesin or myosin [5,6]. The forces generated by this molecular prestressing mechanism can be employed to bend the DNA bundles or to actuate the entire structure through enzymatic cleavage at specific sites. In addition to being building blocks for nanostructures, tensile structural elements made of single-stranded DNA could be used to study molecular forces, cellular mechanotransduction, and other fundamental biological processes.

DNA is not only in the focus of modern molecular biology, but also plays an increasingly important role as a building block for nanoscale materials and devices. In recent years, many researchers in nanoscience have used the unique, programmable molecular recognition properties of DNA to build nanostructures by self-assembly and to realize artificial, machine-like devices. We here give a brief survey of this field and discuss the possible applications of DNA-based nanodevices either as nanoscale motors and actuators, or as novel biosensors with built-in information-processing capability.

Advances in the control of the shape, bonding direction and valency of DNA-coated nanoparticles allow the synthesis of nanoparticle crystallites of ever increasing complexity.

Cytotoxicity of CdSe and CdSe/ZnS nanoparticles has been investigated for different surface modifications such as coating with mercaptopropionic acid, silanization, and polymer coating. For all cases, quantitative values for the onset of cytotoxic effects in serum-free culture media are given. These values are correlated with microscope images in which the uptake of the particles by the cells has been investigated. Our data suggest that in addition to the release of toxic Cd(2+) ions from the particles also their surface chemistry, in particular their stability toward aggregation, plays an important role for cytotoxic effects. Additional patch clamp experiments investigate effects of the particles on currents through ion channels.

We present the concept of multifunctional nanoengineered polymer capsules and outline their applications as new drug delivery systems or supramolecular toolboxes containing, for example, enzymes capable of converting nontoxic prodrugs into toxic drugs at a designated location. Such functionalized nanocontainers offer a wide range of applications including enzymatic catalysis, controlled release, and directed drug delivery in medicine due to their multifunctionality. The unique advantage of capsules in comparison to other systems is that they can be functionalized or loaded simultaneously with the above-mentioned components, thus permitting multifunctional processes in single cells.

A general strategy is described which allows for transferring hydrophobically capped nanocrystals from organic to aqueous solution by wrapping an amphiphilic polymer around the particles. In particular, high quality CoPt3, Au, CdSe/ZnS, and Fe2O3 nanocrystals have been water-solubilized in this way. Analysis with transmission electron microscopy, gel electrophoresis, and fluorescence correlation spectroscopy demonstrates that monodispersity of the particles is conserved upon phase transfer to aqueous solution.

Self-assembled DNA nanostructures have been used to create man-made transmembrane channels in lipid bilayers. Here, we present a DNA-tile structure with a nominal subnanometer channel and cholesterol-tags for membrane anchoring. With an outer diameter of 5 nm and a molecular weight of 45 kDa, the dimensions of our synthetic nanostructure are comparable to biological ion channels. Because of its simple design, the structure self-assembles within a minute, making its creation scalable for applications in biology. Ionic current recordings demonstrate that the tile structures enable ion conduction through lipid bilayers and show gating and voltage-switching behavior. By demonstrating the design of DNA-based membrane channels with openings much smaller than that of the archetypical six-helix bundle, our work showcases their versatility inspired by the rich diversity of natural membrane components.

Plasmonic sensors are extremely promising candidates for label-free single molecule analysis but require exquisite control over the physical arrangement of metallic nanostructures. We employ self-assembly based on the DNA origami technique for accurate positioning of individual 40 nm gold nanoparticles with gaps of 3.3±1 nm. This is probed through far field scattering measurements on individual dimers. This plasmonic coupling allows us to use surface enhanced Raman scattering (SERS) to detect a small number of dye molecules as well as short single-stranded DNA oligonucleotides in the vicinity of the dimers. This demonstrates that DNA origami is a powerful tool with great potential for a wide variety of biosensing and single-molecule applications.

Plasmonic sensors are extremely promising candidates for label-free single-molecule analysis but require exquisite control over the physical arrangement of metallic nanostructures. Here we employ self-assembly based on the DNA origami technique for accurate positioning of individual gold nanoparticles. Our innovative design leads to strong plasmonic coupling between two 40 nm gold nanoparticles reproducibly held with gaps of 3.3±1 nm. This is confirmed through far field scattering measurements on individual dimers which reveal a significant red shift in the plasmonic resonance peaks, consistent with the high dielectric environment due to the surrounding DNA. We use surface-enhanced Raman scattering (SERS) to demonstrate local field enhancements of several orders of magnitude through detection of a small number of dye molecules as well as short single-stranded DNA oligonucleotides. This demonstrates that DNA origami is a powerful tool for the high-yield creation of SERS-active nanoparticle assemblies with reliable sub-5 nm gap sizes. DNA origami is a versatile fabrication approach for building tailored nanostructures. Thacker et al.apply it to the assembly of gold nanoparticle dimers with sub-5 nm gaps and show how the resulting plasmonic resonances can be exploited for surface-enhanced Raman scattering.

A reconfigurable plasmonic nanosystem combines an active plasmonic structure with a regulated physical or chemical control input. There have been considerable efforts on integration of plasmonic nanostructures with active platforms using top-down techniques. The active media include phase-transition materials, graphene, liquid crystals and carrier-modulated semiconductors, which can respond to thermal, electrical and optical stimuli. However, these plasmonic nanostructures are often restricted to two-dimensional substrates, showing desired optical response only along specific excitation directions. Alternatively, bottom-up techniques offer a new pathway to impart reconfigurability and functionality to passive systems. In particular, DNA has proven to be one of the most versatile and robust building blocks for construction of complex three-dimensional architectures with high fidelity. Here we show the creation of reconfigurable three-dimensional plasmonic metamolecules, which execute DNA-regulated conformational changes at the nanoscale. DNA serves as both a construction material to organize plasmonic nanoparticles in three dimensions, as well as fuel for driving the metamolecules to distinct conformational states. Simultaneously, the three-dimensional plasmonic metamolecules can work as optical reporters, which transduce their conformational changes in situ into circular dichroism changes in the visible wavelength range.

We demonstrate a reconfigurable 3D plasmonic nanomachine, which operates in the visible wavelength range. The conformation of this 3D nanomachine can be actively switched through DNA-mediated molecular processes in a fully programmable manner.

Circular dichroism spectra of naturally occurring molecules and also of synthetic chiral arrangements of plasmonic particles often exhibit characteristic bisignate shapes. Such spectra consist of peaks next to dips (or vice versa) and result from the superposition of signals originating from many individual chiral objects oriented randomly in solution. Here we show that by first aligning and then toggling the orientation of DNA-origami-scaffolded nanoparticle helices attached to a substrate, we are able to reversibly switch the optical response between two distinct circular dichroism spectra corresponding to either perpendicular or parallel helix orientation with respect to the light beam. The observed directional circular dichroism of our switchable plasmonic material is in good agreement with predictions based on dipole approximation theory. Such dynamic metamaterials introduce functionality into soft matter-based optical devices and may enable novel data storage schemes or signal modulators., Plasmonic resonances in nanoparticle helices arranged by the DNA origami method can give rise to strong circular dichroism at visible wavelengths. Schreiber et al. show that aligning and then toggling the orientation of such nanoparticle helices enables reversible switching of the dichroic response.

Over the last decades, DNA has proven to be an excellent choice for the designed self-assembly of functional two- and three-dimensional nanostructures and materials [1,2]. By offering attachment sites for active nano-components on DNA-based objects, our group has realized complex and nanometer-precise assemblies of fluorophores, plasmonic nanoparticles and biomolecules [3].

We report a method for simultaneous ionic current measurements of single molecules across up to 16 solid state nanopore channels. Each device, costing less than $20, contains 16 glass nanopores made by laser assisted capillary pulling. We demonstrate simultaneous multichannel detection of double stranded DNA and trapping of DNA origami nanostructures to form hybrid nanopores.

Nanopillars are promising nanostructures composed of various materials that bring new functionalities for applications ranging from photovoltaics to analytics. We developed DNA nanopillars with a height of 220 nm and a diameter of ~14 nm using the DNA origami technique. Modifying the base of the nanopillars with biotins allowed selective, upright, and rigid immobilization on solid substrates. With the help of site-selective dye labels, we visualized the structure and determined the orientation of the nanopillars by three-dimensional fluorescence superresolution microscopy. Because of their rigidity and nanometer-precise addressability, DNA origami nanopillars qualify as scaffold for the assembly of plasmonic devices as well as for three-dimensional superresolution standards.

We review the current developments of DNA-based nanostructures for drug delivery, immunotherapy, diagnostics and molecular biology. DNA is a powerful building block, which by the nature of predictable base pairing, allows the creation of molecular scaffolds, cages and multifunctional carriers with nanoscale dimensions. These engineered constructs have unsurpassed structural qualities such as full control over size, shape and dispersity. Site-specific surface modification enables the presentation of biomolecules at defined distances and stochiometries, which allows tailored cell targeting and substance delivery on demand. As the first successful in vivo applications of DNA nanostructures have recently been demonstrated, we now expect a burst of biomedical studies involving this rapidly progressing technology.

Designing nanoscale objects with the potential to perform externally-controlled motion in biological environments is one of the most sought-after objectives in nanotechnology. Different types of chemically and physically-powered motors have been prepared at the macro- and microscale. However, the preparation of nanoscale objects with a complex morphology, and the potential for light-driven motion has remained elusive to date. Here, we go a step forward by designing a nanoscale hybrid with a propeller-resembling shape, which can be controlled by focused light under biological conditions. Our hybrid, hereafter ‘Au@DNA-origami’, consists of a spherical gold nanoparticle with self-assembled, biocompatible, two-dimensional (2D) DNA sheets on its surface. As a first step towards the potential utilization of these nanoscale objects as light-driven assemblies in biological environments, we show that they can be optically trapped, and hence translated and deposited on-demand, and that under realistic trapping conditions the thermally-induced dehybridization of the DNA sheets can be avoided.