SCIENCE SCIENCE & & TECHNOLOGY TECHNOLOGY
from the SCENEs FROM THE BIOLOGICAL SCENE
SILICON NITRIDE MICROTUBES DIRECT NEURON GROWTH Researchers report that they can direct the growth of neurons in the lab using silicon nitride microtubes (ACS Nano 2014, DOI: 10.1021/nn504876y). The scientists hope that the tubes will allow them to build interfaces between neurons and electronics, possibly leading to new cochlear implants or prosthetic limbs with an almost natural sense of touch. Justin C. Williams of the University of Wisconsin, Madison, and
FROM THE ANALYTICAL SCENE
CHIP SCALES UP METASTASIS STUDIES
ACS NANO
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Xiuling Li of the University of Illinois, Urbana-Champaign, found that cultured cortical neurons on glass slides grow aimlessly until they bump into one of the 4.4-µm-diameter, 50-µmlong transparent microtubes. When the axon, the connection-forming arm of the cell, enters the tube, its growth accelerates 20-fold. The cell body remains outside while the axon snakes through. Williams thinks that the axons’ growth speeds up because they have more
sized wells on a polydimethylsiloxane plate. After adding cells to the wells, the team covered them with collagen gel and then a layer of nutrients. The diffusion of nutrients through the gel created a gradient, mimicking the nutrient gra-
J. AM. CHEM. SOC.
When cancer cells break off from a tumor during metastasis, their first step is to move toward and invade a blood vessel. Now, researchers have developed a three-dimensional, high-throughput assay that mimics cancer cell invasion, automatically tracking cell movements in 4,000 wells at a time (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja5072114). The new tool will allow researchers to test the behavior of genetically altered cell lines and screen for compounds This micrograph shows dient close to a blood that inhibit cancer cell migraa portion of a 4,000-well vessel. An automated tion. Lidong Qin of Houston plate used to study Methodist Research Institute fluorescence microcancer cell invasion. and his group miniaturized scope imaged each well and automated existing 3-D at various depths over assays that follow the movement of time, tracking invasive cancer cells as cancer cells through a porous gel. The they rose toward the highest nutrient researchers manufactured the nanoliter- concentration.
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NOVEMBER 24, 2014
The axon of this neuron has grown through a silicon nitride tube on a glass slide. The round cell body is visible at the top of the image.
surface area to grab onto inside the tubes, compared with the flat surface of the glass slide. Also, silicon nitride has an intrinsic surface charge that may provide a stimulating cue to the cells, he says. The team hopes to next incorporate chemical sensors inside the tubes to measure neuronal activity.
FRO M THE MATERIALS SCENE
LIQUID CRYSTALS STABILIZE DYE SOLAR CELLS Dye-sensitized solar cells (DSCs) could lead to inexpensive, easy-to-manufacture photovoltaics. But they don’t work very well at high temperatures, which can be a problem for a device designed to absorb sunlight. To address this limitation, researchers have made a new electrolyte by combining a liquid crystal with an ionic liquid. By doing so, they produced a DSC that works at up to 120 °C, the highest reported working temperature for such solar cells (Chem. Mater. 2014, DOI: 10.1021/ cm503090z). Ionic liquids, which have high conductivities and low volatilities, make promising electrolytes, but they become unstable at high temperatures. So Takashi Kato of the University of Tokyo and his colleagues added a carbonate-based liquidcrystal molecule that self-assembles into a layered nanostructure with channels that transport ions efficiently. Because the liquid crystals remain stable at high temperatures, the electrolyte mixture remains stable as well. At 90 °C, the solar cell converted 2.7% of collected light into electricity. Kato hopes to increase the efficiency of his cells to 8 to 10%, which should be enough to make them commercially viable.
