Nanoscale Heat Transfer from Magnetic Nanoparticles and Ferritin in an Alternating Magnetic Field

Recent suggestions of nanoscale heat confinement on the surface of synthetic and biogenic magnetic nanoparticles during heating by radio frequency-alternating magnetic fields have generated intense interest because of the potential utility of this phenomenon for noninvasive control of biomolecular and cellular function. However, such confinement would represent a significant departure from the classical heat transfer theory. Here, we report an experimental investigation of nanoscale heat confinement on the surface of several types of iron oxide nanoparticles commonly used in biological research, using an all-optical method devoid of the potential artifacts present in previous studies. By simultaneously measuring the fluorescence of distinct thermochromic dyes attached to the particle surface or dissolved in the surrounding fluid during radio frequency magnetic stimulation, we found no measurable difference between the nanoparticle surface temperature and that of the surrounding fluid for three distinct nanoparticle types. Furthermore, the metalloprotein ferritin produced no temperature increase on the protein surface nor in the surrounding fluid. Experiments mimicking the designs of previous studies revealed potential sources of the artifacts. These findings inform the use of magnetic nanoparticle hyperthermia in engineered cellular and molecular systems

Nanoscale Heat Transfer from Magnetic Nanoparticles and Ferritin in an Alternating Magnetic Field

Recent suggestions of nanoscale heat confinement on the surface of synthetic and biogenic magnetic nanoparticles during heating by radio frequency-alternating magnetic fields have generated intense interest because of the potential utility of this phenomenon for noninvasive control of biomolecular and cellular function. However, such confinement would represent a significant departure from the classical heat transfer theory. Here, we report an experimental investigation of nanoscale heat confinement on the surface of several types of iron oxide nanoparticles commonly used in biological research, using an all-optical method devoid of the potential artifacts present in previous studies. By simultaneously measuring the fluorescence of distinct thermochromic dyes attached to the particle surface or dissolved in the surrounding fluid during radio frequency magnetic stimulation, we found no measurable difference between the nanoparticle surface temperature and that of the surrounding fluid for three distinct nanoparticle types. Furthermore, the metalloprotein ferritin produced no temperature increase on the protein surface nor in the surrounding fluid. Experiments mimicking the designs of previous studies revealed potential sources of the artifacts. These findings inform the use of magnetic nanoparticle hyperthermia in engineered cellular and molecular systems

Megahertz-wave-transmitting conducting polymer electrode for device-to-device integration

The ideal combination of high optical transparency and high electrical conductivity, especially at very low frequencies of less than the gigahertz (GHz) order, such as the radiofrequencies at which electronic devices operate (tens of kHz to hundreds of GHz), is fundamental incompatibility, which creates a barrier to the realization of enhanced user interfaces and ‘device-to-device integration.’ Herein, we present a design strategy for preparing a megahertz (MHz)-transparent conductor, based on a plasma frequency controlled by the electrical conductivity, with the ultimate goal of device-to-device integration through electromagnetic wave transmittance. This approach is verified experimentally using a conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), the microstructure of which is manipulated by employing a solution process. The use of a transparent conducting polymer as an electrode enables the fabrication of a fully functional touch-controlled display device and magnetic resonance imaging (MRI)-compatible biomedical monitoring device, which would open up a new paradigm for transparent conductors. © 2019, The Author(s

A Mechanogenetic Toolkit for Interrogating Cell Signaling in Space and Time

Tools capable of imaging and perturbing mechanical signaling pathways with fine spatiotemporal resolution have been elusive, despite their importance in diverse cellular processes. The challenge in developing a mechanogenetic toolkit (i.e., selective and quantitative activation of genetically encoded mechanoreceptors) stems from the fact that many mechanically activated processes are localized in space and time yet additionally require mechanical loading to become activated. To address this challenge, we synthesized magnetoplasmonic nanoparticles that can image, localize, and mechanically load targeted proteins with high spatiotemporal resolution. We demonstrate their utility by investigating the cell-surface activation of two mechanoreceptors: Notch and E-cadherin. By measuring cellular responses to a spectrum of spatial, chemical, temporal, and mechanical inputs at the single-molecule and single-cell levels, we reveal how spatial segregation and mechanical force cooperate to direct receptor activation dynamics. This generalizable technique can be used to control and understand diverse mechanosensitive processes in cell signaling. VIDEO ABSTRACT

Interfacing with the Brain: How Nanotechnology Can Contribute

Interfacing artificial devices with the human brain is the central goal of neurotechnology. Yet, our imaginations are often limited by currently available paradigms and technologies. Suggestions for brain-machine interfaces have changed over time, along with the available technology. Mechanical levers and cable winches were used to move parts of the brain during the mechanical age. Sophisticated electronic wiring and remote control have arisen during the electronic age, ultimately leading to plug-and-play computer interfaces. Nonetheless, our brains are so complex that these visions, until recently, largely remained unreachable dreams. The general problem, thus far, is that most of our technology is mechanically and/or electrically engineered, whereas the brain is a living, dynamic entity. As a result, these worlds are difficult to interface with one another. Nanotechnology, which encompasses engineered solid-state objects and integrated circuits, excels at small length scales of single to a few hundred nanometers and, thus, matches the sizes of biomolecules, biomolecular assemblies, and parts of cells. Consequently, we envision nanomaterials and nanotools as opportunities to interface with the brain in alternative ways. Here, we review the existing literature on the use of nanotechnology in brain-machine interfaces and look forward in discussing perspectives and limitations based on the authors' expertise across a range of complementary disciplines─from neuroscience, engineering, physics, and chemistry to biology and medicine, computer science and mathematics, and social science and jurisprudence. We focus on nanotechnology but also include information from related fields when useful and complementary

Mechanistic Studies of the Chemical Vapor Deposition of Ceramic and Metal Films From Organometallic Precursors

158 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.Investigations of the thermolysis of tetra(neopentyl)titanium (TiNp\sb4) in solution have been carried out in parallel with studies of the chemical mechanism responsible for its conversion to titanium carbide under CVD conditions. A kinetic isotope effect (k\sb{\rm\alpha (H)}/k\sb{\rm\alpha (D)} = 5.2 \pm 0.4) upon deuterating the alkyl groups at the $\alpha$ positions provides clear evidence that the initial step in the thermolysis is an $\alpha$-hydrogen elimination reaction to form neopentane. The activation parameters for this $\alpha$-hydrogen elimination process are \rm\Delta H\sp\ddagger = 21.5 \pm 1.4 kcal/mol and \rm\Delta S\sp\ddagger = -16.6 \pm 3.8 cal/mol K.The chemical pathway responsible for the conversion of TiNp\sb4 to TiC has been studied. For every equivalent of TiNp\sb4 consumed in the deposition process, 3.25 equiv of neopentane and 0.16 equiv of isobutane are produced; other organic species are also formed but in relatively small amounts. Thermolysis of the specifically deuterated analogue TiNp\sb4-d\sb8 yields a 2.25:1 ratio of neopentane-d\sb3 and neopentane-d\sb2; this result combined with a kinetic isotope effect of 4.9 at 385 K shows that the first step in the deposition pathway under CVD conditions is $\alpha$-hydrogen elimination. The $\alpha$-hydrogen elimination step produces one equivalent of neopentane and a titanium alkylidene, which undergoes further $\alpha$- (and eventually $\gamma$-) hydrogen activation processes to generate the second and third equivalents of neopentane.The deposition of amorphous MoS\sb2 and TiS\sb2 thin films from the metal-organic precursors Mo(S-t-Bu)\sb4 and Ti(S-t-Bu)\sb4 has been investigated. Stoichiometric films nearly free of oxygen and carbon contaminants can be grown at temperatures between 110 and 350\sp\circC and low pressure. For TiS\sb2, the deposition apparatus was treated with TiCl\sb4 before the deposition runs to remove adventitious water and reduce the amount of oxygen impurities. The organic by-products generated during deposition consist principally of isobutylene and tert-butylthiol; smaller amounts of hydrogen sulfide, di(tert-butyl)sulfide, and di(tert-butyl)disulfide are also generated.The organometallic compounds bis(allyl)zinc and bis(2-methylallyl)zinc have been investigated as MOCVD precursors for the deposition of zinc at temperatures as low as 150\sp\circC. The deposits consist of aggregates of hexagonal plates and columns. Analyses of the organic byproduct distribution and in situ spectroscopic studies on single crystal Cu(111) surfaces show that bis(allyl)zinc adsorbs molecularly at temperatures below 200 K, but that the allyl groups transfer to the copper surface at 250 K; the surface-bound allyl groups are bound in a trihapto fashion. On fresh surfaces, the allyl groups fragment to adsorbed hydrogen atoms and hydrocarbon fragments; the former react with intact allyl groups to give propene while the latter eventually give rise to a carbonaceous overlayer. (Abstract shortened by UMI.)U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Chemistry in Korea: IBS and Beyond

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