Abstracts of the 2023 49th Annual NATAS Conference.

We are pleased to announce that the 49th annual meeting of NATAS cwill be held in Rockville, MD, a beautiful city that is part of the Washington D.C. National Capital Area, on the DC metro system (allowing easy access to Washington museums and sites), and close to the National Institute of Standards and Technology (NIST), National Institutes of Health (NIH), Naval Research Laboratory (NRL), Army Research Laboratory (ARL), Johns Hopkins University Applied Physics Laboratory (JHU-APL), Naval Surface Warfare Center (NSWC), Georgetown University, George Washington University, George Mason University, and the University of Maryland.

Polyethyleneimine/polyethylene glycol-conjugated gold nanoparticles as nanoscale positive/negative controls in nanotoxicology: testing in frog embryo teratogenesis assay- and mammalian tissue culture system.

Despite the great potential of using positively charged gold nanoparticles (AuNPs) in nanomedicine, no systematic studies have been reported on their synthesis optimization or colloidal stability under physiological conditions until a group at the National Institute of Standards and Technology recently succeeded in producing remarkably stable polyethyleneimine (PEI)-coated AuNPs (Au-PEI). This improved version of Au-PEI (Au-PEI25kB) has increased the demand for toxicity and teratogenicity information for applications in nanomedicine and nanotoxicology. In vitro assays for Au-PEI25kB in various cell lines showed substantial active cytotoxicity.

Crystallize It before It Diffuses: Kinetic Stabilization of Thin-Film Phosphorus-Rich Semiconductor CuP.

Numerous phosphorus-rich metal phosphides containing both P-P bonds and metal-P bonds are known from the solid-state chemistry literature. A method to grow these materials in thin-film form would be desirable, as thin films are required in many applications and they are an ideal platform for high-throughput studies. In addition, the high density and smooth surfaces achievable in thin films are a significant advantage for characterization of transport and optical properties.

Growth and Decomposition of Pt Surface Oxides.

The formation and thermal stability of Pt surface oxides on a Pt thin film were studied using ambient-pressure X-ray photoelectron spectroscopy. At an oxygen pressure of 73 Pa (550 mTorr), the surface Pt oxide was gradually formed, evidenced by the O 1s peak at 529.5 eV as the Pt film was heated.

Practical Guide to the Design, Fabrication, and Calibration of NIST Nanocalorimeters.

We report here on the design, fabrication, and calibration of nanocalorimeter sensors used in the National Institute of Standards and Technology (NIST) Nanocalorimetry Measurements Project. These small-scale thermal analysis instruments are produced using silicon microfabrication approaches. A single platinum line serves as both the heater and temperature sensor, and it is made from a 500 μm wide, 100 nm thick platinum trace, suspended on a 100 nm thick silicon nitride membrane for thermal isolation.

Multi-environment Nanocalorimeter with Electrical Contacts for Use in the Scanning Electron Microscope.

We have developed a versatile nanocalorimeter sensor which allows imaging and electrical measurements of samples under different gaseous environments using the scanning electron microscope (SEM) and can simultaneously measure the sample temperature and associated heat of reaction. This new sensor consists of four independent heating/sensing elements for nanocalorimetry and eight electrodes for electrical measurements, all mounted on a 50 nm thick, 250 μm × 250 μm suspended silicon nitride membrane. This membrane is highly electron transparent and mechanically robust enabling SEM observation under realistic temperatures, environmental conditions and pressures up to one atmosphere.

Nanocalorimetry-coupled time-of-flight mass spectrometry: identifying evolved species during high-rate thermal measurements.

We report on measurements integrating a nanocalorimeter sensor into a time-of-flight mass spectrometer (TOFMS) for simultaneous thermal and speciation measurements at high heating rates. The nanocalorimeter sensor was incorporated into the extraction region of the TOFMS system to provide sample heating and thermal information essentially simultaneously with the evolved species identification. This approach can be used to measure chemical reactions and evolved species for a variety of materials.

Hydrated/dehydrated lipid phase transitions measured using nanocalorimetry.

The phase transition evolution with hydration of a model system, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), was investigated with a fast nanocalorimetry system. Using nanocalorimetry, it is possible to measure the gel to liquid phase transitions that occur on millisecond to second time scales and quantify the time to recover the hydrated state. The results show the phase transition occurring in a few milliseconds and the relaxation or recovery time from the dehydrated state back to original hydrated state occurring with times dependent on the local humidity.

Combining nanocalorimetry and dynamic transmission electron microscopy for in situ characterization of materials processes under rapid heating and cooling.

Nanocalorimetry is a chip-based thermal analysis technique capable of analyzing endothermic and exothermic reactions at very high heating and cooling rates. Here, we couple a nanocalorimeter with an extremely fast in situ microstructural characterization tool to identify the physical origin of rapid enthalpic signals. More specifically, we describe the development of a system to enable in situ nanocalorimetry experiments in the dynamic transmission electron microscope (DTEM), a time-resolved TEM capable of generating images and electron diffraction patterns with exposure times of 30 ns-500 ns.

Netrin-1 receptor-deficient mice show age-specific impairment in drug-induced locomotor hyperactivity but still self-administer methamphetamine.

Rationale: The mesocorticolimbic dopamine system undergoes significant reorganization of neuronal connectivity and functional refinement during adolescence. Deleted in colorectal cancer (DCC), a receptor for the guidance cue netrin-1, is involved in this reorganization. Previous studies have shown that adult mice with a heterozygous (het) loss-of-function mutation in DCC exhibit impairments in sensitization and conditioned place preference (CPP) to psychostimulants.

Calcium signaling is gated by a mechanical threshold in three-dimensional environments.

Cells interpret their mechanical environment using diverse signaling pathways that affect complex phenotypes. These pathways often interact with ubiquitous 2(nd)-messengers such as calcium. Understanding mechanically-induced calcium signaling is especially important in fibroblasts, cells that exist in three-dimensional fibrous matrices, sense their mechanical environment, and remodel tissue morphology.

Behavioural correlate of choice confidence in a discrete trial paradigm.

How animals make choices in a changing and often uncertain environment is a central theme in the behavioural sciences. There is a substantial literature on how animals make choices in various experimental paradigms but less is known about the way they assess a choice after it has been made in terms of the expected outcome. Here, we used a discrete trial paradigm to characterise how the reward history shaped the behaviour on a trial by trial basis.

Synthetic protocells interact with viral nanomachinery and inactivate pathogenic human virus.

We present a new antiviral strategy and research tool that could be applied to a wide range of enveloped viruses that infect human beings via membrane fusion. We test this strategy on two emerging zoonotic henipaviruses that cause fatal encephalitis in humans, Nipah (NiV) and Hendra (HeV) viruses. In the new approach, artificial cell-like particles (protocells) presenting membrane receptors in a biomimetic manner were developed and found to attract and inactivate henipavirus envelope glycoprotein pseudovirus particles, preventing infection.

Spaceflight-related suboptimal conditions can accentuate the altered gravity response of Drosophila transcriptome.

Genome-wide transcriptional profiling shows that reducing gravity levels during Drosophila metamorphosis in the International Space Station (ISS) causes important alterations in gene expression: a large set of differentially expressed genes (DEGs) are observed compared to 1g controls. However, the preparation procedures for spaceflight and the nonideal environmental conditions on board the ISS subject the organisms to additional environmental stresses that demonstrably affect gene expression. Simulated microgravity experiments performed on the ground, under ideal conditions for the flies, using the random position machine (RPM), show much more subtle effects on gene expression.

Structural and biomechanical characteristics of the diaphragmatic tendon in infancy and childhood: an initial analysis.

Background: Engineered tendon grafts have been shown, experimentally, to be promising alternatives for partial diaphragmatic replacement. This study was aimed at determining the cellularity, extracellular matrix composition, and biomechanical characteristics of the diaphragmatic tendon in infants and children to be used as a reference for proper diaphragmatic graft engineering.

Methods: The left diaphragmatic tendon was procured at autopsy from 13 patients divided into 2 groups.

Synthetic protocells to mimic and test cell function.

Synthetic protocells provide a new means to probe, mimic and deconstruct cell behavior; they are a powerful tool to quantify cell behavior and a useful platform to explore nanomedicine. Protocells are not simple particles; they mimic cell design and typically consist of a stabilized lipid bilayer with membrane proteins. With a finite number of well characterized components, protocells can be designed to maximize useful outputs.

Self-assembled gold nanoparticle molecular probes for detecting proteolytic activity in vivo.

Target-activatable fluorogenic probes based on gold nanoparticles (AuNPs) functionalized with self-assembled heterogeneous monolayers of dye-labeled peptides and poly(ethylene glycol) have been developed to visualize proteolytic activity in vivo. A one-step synthesis strategy that allows simple generation of surface-defined AuNP probe libraries is presented as a means of tailoring and evaluating probe characteristics for maximal fluorescence enhancement after protease activation. Optimal AuNP probes targeted to trypsin and urokinase-type plasminogen activator required the incorporation of a dark quencher to achieve 5- to 8-fold signal amplification.

Designing artificial cells to harness the biological ion concentration gradient.

Cell membranes contain numerous nanoscale conductors in the form of ion channels and ion pumps that work together to form ion concentration gradients across the membrane to trigger the release of an action potential. It seems natural to ask if artificial cells can be built to use ion transport as effectively as natural cells. Here we report a mathematical calculation of the conversion of ion concentration gradients into action potentials across different nanoscale conductors in a model electrogenic cell (electrocyte) of an electric eel.

Three-dimensional conductive constructs for nerve regeneration.

The unique electrochemical properties of conductive polymers can be utilized to form stand-alone polymeric tubes and arrays of tubes that are suitable for guides to promote peripheral nerve regeneration. Noncomposite, polypyrrole (PPy) tubes ranging in inner diameter from 25 microm to 1.6 mm as well as multichannel tubes were fabricated by electrodeposition.

Poly(glycerol sebacate) nanofiber scaffolds by core/shell electrospinning.

The novel biomaterial poly(glycerol sebacate) (PGS) holds great promise for tissue engineering and regenerative medicine. PGS is a rubbery, degradable polymer much like elastin; however, it has been limited to cast structures. This work reports on the formation of PGS nanofibers in random non-woven mats for use as tissue engineering scaffolds by coaxial core/shell electrospinning.

Drosophila melanogaster, a model system for comparative studies on the responses to real and simulated microgravity.

A key requirement to enhance our understanding of the response of biological organisms to different levels of gravity is the availability of experimental systems that can simulate microgravity and hypergravity in ground-based laboratories. This paper compares the results obtained from analysing gene expression profiles of Drosophila in space versus those obtained in a random position machine (RPM) and by centrifugation. The correlation found validates the use of the RPM simulation technique to establish the effects of real microgravity on biological systems.

Comparative analysis of Drosophila melanogaster and Caenorhabditis elegans gene expression experiments in the European Soyuz flights to the International Space Station.

The European Soyuz missions have been one of the main routes for conducting scientific experiments onboard the International Space Station, which is currently in the construction phase. A relatively large number of life and physical sciences experiments as well as technology demonstrations have been carried out during these missions. Included among these experiments are the Gene experiment during the Spanish "Cervantes" Soyuz mission and the ICE-1st experiment during the Dutch "Delta" mission.

Label-free immunodetection with CMOS-compatible semiconducting nanowires.

Semiconducting nanowires have the potential to function as highly sensitive and selective sensors for the label-free detection of low concentrations of pathogenic microorganisms. Successful solution-phase nanowire sensing has been demonstrated for ions, small molecules, proteins, DNA and viruses; however, 'bottom-up' nanowires (or similarly configured carbon nanotubes) used for these demonstrations require hybrid fabrication schemes, which result in severe integration issues that have hindered widespread application. Alternative 'top-down' fabrication methods of nanowire-like devices produce disappointing performance because of process-induced material and device degradation.

Electropolymerization on microelectrodes: functionalization technique for selective protein and DNA conjugation.

A critical shortcoming of current surface functionalization schemes is their inability to selectively coat patterned substrates at micrometer and nanometer scales. This limitation prevents localized deposition of macromolecules at high densities, thereby restricting the versatility of the surface. A new approach for functionalizing lithographically patterned substrates that eliminates the need for alignment and, thus, is scalable to any dimension is reported.