Nano Focus
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Bio Focus Liquid STEM used for particle uptake studies in living cells
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he uptake of nanoparticles into cells has conventionally been studied with transmission electron microscopy of thin sections. However, the preparation into thin sections leads to a loss of nanoparticles, and also prevents the analysis of the whole three-dimensional cellular volume. Furthermore, conventional electron microscopy is not capable of studying live cells. D.B. Peckys and N. de Jonge from Vanderbilt University Medical Center have now improved upon a liquid scanning transmission electron microscopy (STEM ) method that allows for quantitative assessment of nanoparticle uptake in living cells. The researchers used a microfluidic chamber composed of microchips where fibroblast cells were imaged with minimal radiation damage to reveal the distribution of gold-nanoparticles (Au-NP) within the cells. In the March 16th issue of Nano Let-
Nano Focus Nanofiltration membrane improves performance of vanadium redox flow battery
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ntegrating renewable energy sources such as wind and solar into the electric grid will require energy storage systems to handle their intermittent nature. One promising possibility is the vanadium redox flow battery (VRB), based on active species of vanadium dissolved in electrolyte. To date, VRBs have been limited by their use of perfluorinated-polymer ionexchange membranes, which are expensive and have low selectivity between vanadium and other ions. Now a group from the Dalian Institute of Chemical
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VOLUME 36 • JUNE 2011
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because of the energy penalty due to recycling the material, the researchers said that “the ability to fine tune CO2 affinity in this way [with the selection of
functional groups] is of potential value for both CO2 capture and storage as well as gas separation.” Steven Trohalaki
ters (DOI: 10.1021/nl200285r; p. 1733), the research team described the application of a novel microfluidic chamber device for live-cell examination. The device was made from two parallel silicon microchips. Each microchip contained a central silicon nitride (SiN) membrane of 50 nm thickness that was transparent to the electron beam as well as light. One microchip was coated with poly-L-lysine (PLL) for increased cell adherence; the other chip had an attached 6 μm spacer to form a reservoir for the cells and buffer. Live green monkey kidney fibroblast cells (COS-7) were incubated for 2 hours in the presence of 30 nm Au-NPs. The cells were then washed and incubated in a medium. Twenty-four hours later, the cells were enclosed in the chamber and imaged live with a STEM under a continuous flow of buffer. Experiments demonstrated that COS-7 cells remained viable in the microfluidic chamber. STEM analysis was carried out shortly after the cells were loaded. The cells were viewed at 16,000x magnification using an accelerating voltage of
200 kV and a probe current of 0.16 nA. The researchers were seeking to identify several quantitative values pertaining to the number and placement of the AuNPs inside t
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