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Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity ( T2) contrast agents in magnetic resonance imaging (MRI). Organizing small ( D<10 nm) SPIONs into large assemblies can considerably enhance their relaxivity. However, this assembly process is difficult to control and can easily result in unwanted aggregation and precipitation, which might further lead to lower contrast agent performance. Herein, we present highly stable protein-polymer double-stabilized SPIONs for improving contrast in MRI. We used a cationic-neutral double hydrophilic poly( N-methyl-2-vinyl pyridinium iodide- block-poly(ethylene oxide) diblock copolymer (P2QVP- b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2O3) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface ( pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter ( Dh) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity ( r1) is decreased and the transverse relaxivity ( r2) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement. [ABSTRACT FROM AUTHOR]

Polyelectrolytes are promising electronicallyinsulating layers for low-voltage organic field effect transistors.However, the polyelectrolyte–semiconductor interface is difficultto manufacture due to challenges in wettability. We introduce an amphiphilicsemiconducting copolymer which, when spread as a thin film, can changeits surface from hydrophobic to hydrophilic upon exposure to water.This peculiar wettability is exploited in the fabrication of polyelectrolyte-gatedfield-effect transistors operating below 0.5 V. The prepared amphiphilicsemiconducting copolymer is based on a hydrophobic regioregular poly(3-hexylthiophene)(P3HT) covalently linked to a hydrophilic poly(sulfonated)-based randomblock. Such a copolymer is obtained in a three-step strategy combiningGrignard metathesis (GRIM), atom transfer radical polymerization (ATRP)processes, and a postmodification method. The structure of the diblockcopolymer was characterized using FT-IR, 1H NMR spectroscopy,and gel permeation chromatography (GPC). [ABSTRACT FROM AUTHOR]

In soft materials, self-assembled nanoscale structures can allow new functionalities but a general problem is to align such local structures aiming at monodomain overall order. In order to achieve shear alignment in a controlled manner, a novel type of rheo-optical apparatus has here been developed that allows small sample volumes and in situ monitoring of the alignment process during the shear. Both the amplitude and orientation angles of low level linear birefringence and dichroism are measured while the sample is subjected to large amplitude oscillatory shear flow. The apparatus is based on a commercial rheometer where we have constructed a flow cell that consists of two quartz teeth. The lower tooth can be set in oscillatory motion whereas the upper one is connected to the force transducers of the rheometer. A custom made cylindrical oven allows the operation of the flow cell at elevated temperatures up to 200 °C. Only a small sample volume is needed (from 9 to 25 mm3), which makes the apparatus suitable especially for studying new materials which are usually obtainable only in small quantities. Using this apparatus the flow alignment kinetics of a lamellar polystyrene-b-polyisoprene diblock copolymer is studied during shear under two different conditions which lead to parallel and perpendicular alignment of the lamellae. The open device geometry allows even combined optical/x-ray in situ characterization of the alignment process by combining small-angle x-ray scattering using concepts shown by Polushkin et al. [Macromolecules 36, 1421 (2003)]. [ABSTRACT FROM AUTHOR]

We investigate the possibility to maintain an electric polarization in an organic bilayer via ion trapping, i.e., without any external bias. In the cryptand-polyanion bilayer, ions of specific size can be strongly coordinated with organic macrocyclic molecules. Cations move from the polyanion layer to the cryptand layer upon applying a bias and are trapped in this layer. As a result, the voltage dependence of the polarization displays a hysteresis. The bilayer is then advantageously used as an electronic insulating layer in an organic field effect transistor. The ions trapping and de-trapping can be followed by the amplitude of the threshold voltage (Vth) shift as well as its temporal evolution. [ABSTRACT FROM AUTHOR]

The working principles of thin film organic memory devices remain debated and tunability has been less presented. We show that the nanostructure of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and polystyrene (PS) allows facile tuning of switching behavior for low PCBM concentrations upon annealing above the glass transition temperature of PS. By increasing the PCBM concentration from 2 to 6 wt %, the switching voltage from off to on state during the first voltage sweep systematically decreases. In subsequent voltage sweeps negative differential resistance effect is observed. Above ca. 7 wt %, chains of PCBM clusters couple the electrodes, which leads to Ohmic behavior. [ABSTRACT FROM AUTHOR]

Binary nanoparticle superlattices are periodic nanostructures with lattice constants much shorter than the wavelength of light and could be used to prepare multifunctional metamaterials. Such superlattices are typically made from synthetic nanoparticles, and although biohybrid structures have been developed, incorporating biological building blocks into binary nanoparticle superlattices remains challenging. Protein-based nanocages provide a complex yet monodisperse and geometrically well-defined hollow cage that can be used to encapsulate different materials. Such protein cages have been used to program the self-assembly of encapsulated materials to form free-standing crystals and superlattices at interfaces or in solution. Here, we show that electrostatically patchy protein cages-cowpea chlorotic mottle virus and ferritin cages-can be used to direct the self-assembly of three-dimensional binary superlattices. The negatively charged cages can encapsulate RNA or superparamagnetic iron oxide nanoparticles, and the superlattices are formed through tunable electrostatic interactions with positively charged gold nanoparticles. Gold nanoparticles and viruses form an AB8fcc crystal structure that is not isostructural with any known atomic or molecular crystal structure and has previously been observed only with large colloidal polymer particles. Gold nanoparticles and empty or nanoparticle-loaded ferritin cages form an interpenetrating simple cubic AB structure (isostructural with CsCl). We also show that these magnetic assemblies provide contrast enhancement in magnetic resonance imaging. [ABSTRACT FROM AUTHOR]

During the COVID-19 pandemic, physical activity levels have decreased by ~30% and sitting time has increased by ~30%. Recent call to actions by the ACSM and Physiological Society have urged widespread promotion and implementation of physical activity to keep communities healthy. PURPOSE: To leverage Exercise is Medicine on Campus (EIM-OC) and promote healthy living behaviors in our rural community during the pandemic. Specifically, we aimed to: 1) assess current levels of physical activity in the community, 2) increase public awareness about staying physically active during the pandemic and 3) offer a community physical activity program. METHODS: A team of kinesiology and biology students (n=10) led our EIM-OC initiative. Levels of physical activity in the community were assessed through an online survey. Public awareness about physical activity was promoted through an infographic, virtual town hall, and discussion with health care providers. A 10-wk physical activity program was delivered through ZOOM and social media and included live workouts (3x/wk) consisting of home-based activities (e.g., aerobic exercise, resistance exercise using common household items, yoga). RESULTS: Twenty-nine adults (51±17yrs, 28±6BMI) completed the survey. Majority of adults (72%) reported they were less physically active during the pandemic and 45% indicated that they had been encouraged by a health professional to remain active. Our message of staying physically active during the pandemic was communicated through website, email, radio, newspaper, social media, and state health department. More than 35 guided workouts (30-60 min) were delivered to healthy adults and those with reduced mobility. The physical activity program was also expanded to create a University-wide physical education course (50 students, 1 credit). CONCLUSIONS: Adults in our rural community reported they were moving less and not well informed about the importance of physically activity during the pandemic. As local health departments are currently overburdened with managing COVID-19, it is imperative for exercise specialists to help facilitate and communicate the importance of physical activity. EIM-OC provided a robust platform for us to deliver critical physical activity resources and keep our community active during the COVID-19 pandemic. [ABSTRACT FROM AUTHOR]