Label-Free Digital Holotomography Reveals Ibuprofen-Induced Morphological Changes to Red Blood Cells.

Understanding the dose-dependent effect of over-the-counter drugs on red blood cells (RBCs) is crucial for hematology and digital pathology. Yet, it is challenging to continuously record the real-time, drug-induced shape changes of RBCs in a label-free manner. Here, we demonstrate digital holotomography (DHTM)-enabled real-time, label-free concentration-dependent and time-dependent monitoring of ibuprofen on RBCs from a healthy donor. The RBCs are segmented based on three-dimensional (3D) and four-dimensional (4D) refractive index tomograms, and their morphological and chemical parameters are retrieved with their shapes classified using machine learning. We directly observed the formation and motion of spicules on the RBC membrane when aqueous solutions of ibuprofen were drop-cast on wet blood, creating rough-membraned echinocyte forms. At low concentrations of 0.25-0.50 mM, the ibuprofen-induced morphological change was transient, but at high concentrations (1-3 mM) the spiculated RBC remained over a period of up to 1.5 h. Molecular simulations confirmed that aggregates of ibuprofen molecules at high concentrations significantly disrupted the RBC membrane structural integrity and lipid order but produced negligible effect at low ibuprofen concentrations. Control experiments on the effect of urea, hydrogen peroxide, and aqueous solutions on RBCs showed zero spicule formation. Our work clarifies the dose-dependent chemical effects on RBCs using label-free microscopes that can be deployed for the rapid detection of overdosage of over-the-counter and prescribed drugs

Polymer-Nanocarbon Topological and Electronic Interface

The electronic structure of semiconducting carbon nanotubes selected through polymer functionalization is routinely verified by measuring the spectral van Hove singularity signature under ultraclean vacuum conditions. Interpreting the effect of unperturbed polymer adsorption on the nanotube energetic bands in solvent media is experimentally challenging owing to solvent molecular crowding around the hybrid complex. Here, a liquid-based scanning tunneling microscope and spectroscope operating in a noise free laboratory is used to resolve the polymer-semiconducting carbon-nanotube-underlying graphene heterostructure in the presence of encompassing solvent molecules. The spectroscopic measurements highlight the role of polymer packing and graphene landscape on the electronic shifts induced in the nanotube energy bands. Together with molecular dynamics simulations, our experimental findings emphasize the necessity of recording physicochemical and electronic properties of liquid phase solubilized hybrid materials in their native state

Formation mechanism of metal–molecule–metal junctions: molecule-assisted migration on metal defects

Activation energies, Ea, measured from molecular exchange experiments are combined with atomic-scale calculations to describe the migration of bare Au atoms and Au–alkanethiolate species on gold nanoparticle surfaces during ligand exchange for the creation of metal–molecule–metal junctions. It is well-known that Au atoms and alkanethiol–Au species can diffuse on gold with sub-1 eV barriers, and surface restructuring is crucial for self-assembled monolayer (SAM) formation for interlinking nanoparticles and in contacting nanoparticles to electrodes. In the present work, computer simulations reveal that naturally occurring ridges and adlayers on Au(111) are etched and resculpted by migration of alkanethiolate–Au species toward high coordination kink sites at surface step edges. The calculated energy barrier, Eb, for diffusion via step edges is 0.4–0.7 eV, close to the experimentally measured Ea of 0.5–0.7 eV. By contrast, putative migration from isolated nine-coordinated terrace sites and complete Au unbinding from the surface incur significantly larger barriers of +1 and +3 eV, respectively. Molecular van der Waals packing energies are calculated to have negligible effect on migration barriers for typically used molecules (length < 2.5 nm), indicating that migration inside SAMs does not change the size of the migration barrier. We use the computational methodology to propose a means of creating Au nanoparticle arrays via selective replacement of citrate protector molecules by thiocyanate linker molecules on surface step sites. This work also outlines the possibility of using Au/Pt alloys as possible candidates for creation of contacts that are well-formed and long-lived because of the superior stability of Pt interfaces against atomic migration

Conductance probe microscopy investigation on the local electronic properties of single walled carbon nanotube systems

THESIS 9389In order to build electronic devices and circuits comprised of nanoscale materials as the active element it is imperative to unravel the local electronic properties of these materials. We have performed an in-depth study on the local electronic behavior of individual single walled carbon nanotubes (SWCNT) and on two dimensional networks based on these tubes using conductance imaging atomic force microscopy (CI-AFM). This technique allows us to simultaneously investigate the morphology and the local electronic structure of the nanotubes, when a metal coated tip is scanned over the surface. SWCNTs solubilised in N-methyl pyrrolidone (NMP) were sprayed onto Si02 substrates to form homogeneous and percolating networks. The electrodes were fabricated using UV-lithographically and these samples were subjected to controlled annealing at 500 degrees Celsius under Ar/H2 atmosphere to remove the adsorbed NMP molecules

Nanoelectrical analysis of single molecules and atomic-scale materials at the solid/liquid interface

Evaluating the built-in functionality of nanomaterials under practical conditions is central for their proposed integration as active components in next-generation electronics. Low-dimensional materials from single atoms to molecules have been consistently resolved and manipulated under ultrahigh vacuum at low temperatures. At room temperature, atomic-scale imaging has also been performed by probing materials at the solid/liquid interface. We exploit this electrical interface to develop a robust electronic decoupling platform that provides precise information on molecular energy levels recorded using in situ scanning tunnelling microscopy/spectroscopy with high spatial and energy resolution in a high-density liquid environment. Our experimental findings, supported by ab initio electronic structure calculations and atomic-scale molecular dynamics simulations, reveal direct mapping of single-molecule structure and resonance states at the solid/liquid interface.We further extend this approach to resolve the electronic structure of graphene monolayers at atomic length scales under standard room-temperature operating conditions

3D Holo-tomographic Mapping of COVID-19 Microclots in Blood to Assess Disease Severity

The coronavirus disease 2019 (COVID-19) has impacted health globally. Cumulative evidence points to long-term effects of COVID-19 such as cardiovascular and cognitive disorders, diagnosed in patients even after the recovery period. In particular, micrometer-sized blood clots and hyperactivated platelets have been identified as potential indicators of long COVID. Here, we resolve microclot structures in the plasma of patients with different subphenotypes of COVID-19 in a label-free manner, using 3D digital holo-tomographic microscopy (DHTM). Based on 3D refractive index (RI) tomograms, the size, dry mass, and prevalence of microclot composites were quantified and then parametrically differentiated from fibrin-rich microclots and platelet aggregates in the plasma of COVID-19 patients. Importantly, fewer microclots and platelet aggregates were detected in the plasma of healthy controls compared to COVID-19 patients. Our imaging and analysis workflow is built around a commercially available DHT microscope capable of operation in clinical settings with a 2 h time period from sample preparation and data acquisition to results

Capturing the embryonic stages of self-assembly - design rules for molecular computation

The drive towards organic computing is gaining momentum. Interestingly, the building blocks for such architectures is based on molecular ensembles extending from nucleic acids to synthetic molecules. Advancement in this direction requires devising precise nanoscopic experiments and model calculations to decipher the mechanisms governing the integration of a large number of molecules over time at room-temperature. Here, we report on ultrahigh-resolution scanning tunnelling microscopic measurements to register the motion of molecules in the absence of external stimulus in liquid medium. We observe the collective behavior of individual molecules within a swarm which constantly iterate their position to attain an energetically favourable site. Our approach provides a consistent pathway to register molecular self-assembly in sequential steps from visualising thermodynamically driven repair of defects up until the formation of a stable two-dimensional configuration. These elemental findings on molecular surface dynamics, self-repair and intermolecular kinetic pathways rationalised by atom-scale simulations can be explored for developing new models in algorithmic self-assembly to realisation of evolvable hardware

Sensing of KCl, NaCl, and Pyocyanin with a MOF-Decorated Electrospun Nitrocellulose Matrix

Wearable sensors can provide important insight into a patient’s health status by monitoring the concentration of specific biomarkers in body fluids. Compared to biofluids such as blood or cerebrospinal fluid, which require an invasive acquisition process, other body fluids such as sweat or exhaled air can be easily collected using patches or masks, sufficient for the detection of metabolic and pathological changes. However, the successful integration of an efficient biosensor into textiles or polymer substrates is a challenge if flexibility and functionality are not to be compromised. Here, we demonstrate the integration of nanoporous metal–organic framework (MOF) particles with nitrocellulose (NC) fibrous layers using an electrospinning approach and validate the efficiency of our MOF@NC structure as biosensors. The chemical response of this hybrid nanomaterial upon exposure to different ionic sweat biomarkers such as NaCl and KCl as well as pyocyanin, a biomarker for the nosocomial pathogen Pseudomonas aeruginosa, was investigated using Raman spectroscopy. A change of the Raman intensity at distinct peaks of our MOF-containing architecture occurs after treatment of the material with the analyte solutions. Furthermore, we observed the sensitivities for pyocyanin at the normalized Raman intensity change to be up to −1120 au μm–1, about 4 orders of magnitude larger than for NaCl and KCl. The independence of our architecture from the type of MOF and the possibility of using different MOFs with individual chemistry make this approach a promising platform for versatile and adaptable sensing of biomarkers with high sensitivity and selectivity.ISSN:2574-097

A Robust Molecular Probe for Ångstrom-Scale Analytics in Liquids

Traditionally, nanomaterial profiling using a single-molecule-terminated scanning probe is performed at the vacuum–solid interface often at a few Kelvin, but is not a notion immediately associated with liquid–solid interface at room temperature. Here, using a scanning tunnelling probe functionalized with a single C60 molecule stabilized in a high-density liquid, we resolve low-dimensional surface defects, atomic interfaces and capture Ångstrom-level bond-length variations in single-layer graphene and MoS2. Atom-by-atom controllable imaging contrast is demonstrated at room temperature and the electronic structure of the C60–metal probe complex within the encompassing liquid molecules is clarified using density functional theory. Our findings demonstrates that operating a robust single-molecular probe is not restricted to ultra-high vacuum and cryogenic settings. Hence the scope of high-precision analytics can be extended towards resolving sub-molecular features of organic elements and gauging ambient compatibility of emerging layered materials with atomic-scale sensitivity under experimentally less stringent conditions