Visible wavelength spectral tuning of absorption and circular dichroism of DNA-assembled Au/Ag core-shell nanorod assemblies

Plasmonic nanoparticles have unique properties which can be harnessed to manipulate light at the nanoscale. With recent advances in synthesis protocols that increase their stability, gold-silver core-shell nanoparticles have become suitable building blocks for plasmonic nanostructures to expand the range of attainable optical properties. Here we tune the plasmonic response of gold-silver core-shell nanorods over the visible spectrum by varying the thickness of the silver shell. Through the chiral arrangement of the nanorods with the help of various DNA origami designs, the spectral tunability of the plasmon resonance frequencies is transferred into circular dichroism signals covering the spectrum from 400 nm to 700 nm. Our approach could aid in the construction of better sensors as well as metamaterials with a tunable optical response in the visible region

Propulsion of Magnetic Beads Asymmetrically Covered with DNA Origami Appendages

Eukaryotic cells that swim by the beating of nanoscale elastic filaments (flagella) present a promising locomotion paradigm for man-made analogues essential for next-generation in-vivo treatments and for the study of collective phenomena at the low Reynolds number limit. However, artificial analogues have been limited to many microns in size due to the engineering challenges of fabricating actable flexible filaments at the nanoscale-thereby narrowing the application scope. Here, made-to-order nanoscale filaments designed on the molecular level are fabricated using the DNA-origami technique. It is found that magnetic beads anisotropically covered with such bundles move in a ballistic fashion when wagged back and forth under an external magnetic field. Furthermore, by comparing bead dynamics at a range of bundle coverages and driving frequencies, compelling evidence is amassed to suggest that this ballistic motion is imparted by the beating of the DNA origami filaments as synthetic flagella. This proof-of-concept work opens up avenues for further made-for-purpose appendages designed using DNA self-assembly and with it ever more complex locomotion on the nano and microscale

DNA Origami Fiducial for Accurate 3D Atomic Force Microscopy Imaging

Atomic force microscopy (AFM) is a powerful technique for imaging molecules, macromolecular complexes, and nanoparticles with nanometer resolution. However, AFM images are distorted by the shape of the tip used. These distortions can be corrected if the tip shape can be determined by scanning a sample with features sharper than the tip and higher than the object of interest. Here we present a 3D DNA origami structure as fiducial for tip reconstruction and image correction. Our fiducial is stable under a broad range of conditions and has sharp steps at different heights that enable reliable tip reconstruction from as few as ten fiducials. The DNA origami is readily codeposited with biological and nonbiological samples, achieves higher precision for the tip apex than polycrystalline samples, and dramatically improves the accuracy of the lateral dimensions determined from the images. Our fiducial thus enables accurate and precise AFM imaging for a broad range of applications

Sculpting light using DNA origami-templated nanoparticle assemblies

The optical behavior of materials at the macroscale is influenced by their nanoscale structure. Developing techniques to influence and create new nanoscale architectures can enable us to assemble materials with novel properties. DNA nanotechnology, and especially the DNA origami technique allows the use of self-assembly to arrange nanoscopic objects in user-defined geometries. In this doctoral thesis, we use this feature to engineer the optical response of plasmonic nanoparticle assemblies in two areas: chiral plasmonics and physical unclonable functions (PUFs). Initially, we discuss advances in the use of DNA origami-templated plasmonic materials to achieve sensitive biomolecule detection. We then explore the synthesis and properties of chiral nanorod dimers, focusing on silver-gold core-shell nanorods. Utilising a novel one-pot method, we achieve monodisperse nanorods with precise control over size, aspect ratio, and silver shell thickness. These nanoparticles offer tunable optical characteristics and are functionalized with DNA, enabling their organization into specific chiral geometries via DNA origami. Our findings extend the spectral control over the circular dichroic signal, offering potential applications in catalysis and biosensing. We use the core-shell particles and DNA origami in combination with nanosphere lithography to create a novel unclonable tag to combat counterfeiting. Traditional cryptographic methods based on one-way functions are discussed, along with their limitations, both technological and theoretical. We describe PUFs as an alternative, with an emphasis on optical PUFs, which are robust against various types of attacks and cloning attempts. Our PUFs exhibit a broad range of hues due to plasmonic coupling, enhancing their security features. Moreover, these PUFs are seamlessly integrated with a cost-effective 3D-printed read-out tool, bridging the gap between experimental technology and practical application. The thesis thus contributes significant advancements in using DNA-templated optical materials for both scientific inquiry and societal applications. It showcases the versatility and potential of the DNA origami technique for precise nanoscale assembly and paves the way for practical applications such as secure authentication systems and biochemical sensing.Das optische Verhalten von Materialien auf der Makroebene wird durch ihre Nanostruktur beeinflusst. Die Fähigkeit, neue Nanoarchitekturen zu schaffen und zu gestalten, ermöglicht es uns, Materialien mit neuartigen Eigenschaften zu entwickeln. Die DNA-Nanotechnologie, insbesondere die DNA-Origami-Technik, ermöglicht es mittels Selbstorganisation, um nanoskopische Objekte in benutzerdefinierten Geometrien anzuordnen. In dieser Doktorarbeit nutzen wir dies Eigenschaft, um die optische Reaktion von plasmonischen Nanopartikel-Assemblagen in zwei Bereichen zu steuern: chirale Plasmonik und physisch unkopierbare Funktionen (PUFs). Zunächst diskutieren wir Fortschritte bei der Verwendung mithilfe von DNA-Origami entworfenen plasmonischen Materialien zur empfindlichen Biomoleküldetektion. Dann behandeln wir die Synthese und Eigenschaften von chiralen Nanostab-Dimeren, wobei wir uns auf Silber-Gold Kern-Schale-Nanostäbe konzentrieren. Durch die Verwendung einer neuartigen Ein-Topf-Methode erreichen wir monodisperse Nanostäbe mit präziser Kontrolle über Größe, Seitenverhältnis und Silberschalendicke. Diese Nanopartikel bieten abstimmbare optische Eigenschaften und sind mit DNA funktionalisiert, was ihre Organisation in spezifischen chiralen Geometrien durch DNA-Origami ermöglicht. Unsere Erkenntnisse erweitern die spektrale Kontrolle über das zirkulardichroische Signal und bieten potenzielle Anwendungen in der empfindlichen Biomoleküldetektion. Wir verwenden die Kern-Schale-Partikel und DNA-Origami in Kombination mit Nanosphären-Lithographie, um ein neuartiges, unkopierbares Etikett zur Bekämpfung von Fälschungen zu schaffen. Traditionelle kryptografische Methoden, die auf Einwegfunktionen basieren, werden diskutiert, zusammen mit ihren technologischen und theoretischen Einschränkungen. Wir führen PUFs als Alternative ein, mit einem Schwerpunkt auf optischen PUFs, die gegen verschiedene Arten von Angriffen und Klonversuchen robust sind. Unsere PUFs weisen ein breites Spektrum an Farbtönen aufgrund starker plasmonischer Kopplung auf, was ihre Sicherheitsmerkmale verbessert. Darüber hinaus werden diese PUFs nahtlos mit einem kostengünstigen, 3D-gedruckten Auslesewerkzeug integriert, wodurch die Lücke zwischen experimenteller Technologie und praktischer Anwendung geschlossen wird. Die Arbeit trägt somit wesentlich zur Weiterentwicklung der Verwendung von DNA-templierten optischen Materialien sowohl für die wissenschaftliche Forschung als auch für gesellschaftlich relevante Anwendungen bei. Sie zeigt die Vielseitigkeit und das Potenzial der DNA-Origami-Techniken für die präzise Nano-Assemblierung und ebnet den Weg für praktische Anwendungen wie sichere Authentifizierungssysteme und empfindliche biochemische Sensoren

Chiral Assembly of GoldSilver CoreShell Plasmonic Nanorods on DNA Origami with Strong Optical Activity

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

Cardiovascular magnetic resonance imaging for amyloidosis: The state-of-the-art.

Amyloidosis results from insoluble precursor proteins being deposited in the extracellular compartment. The prognosis of the disease is predominantly determined by cardiac involvement due to amyloid accumulation that contributes to cardiac dysfunction and disturbed conduction of cardiac electrical signals. The clinical and radiological manifestations of amyloidosis are often non-specific, making amyloidosis a diagnostic challenge both for clinicians and radiologists. Cardiovascular magnetic resonance imaging, including conventional sequences, late gadolinium enhancement, T1 mapping and determination of extracellular volume fraction is a multi-dimensional modality for the assessment and diagnosis of cardiac amyloidosis and, in addition, is an excellent tool for risk stratification and disease tracking