SCIENCE & TECHNOLOGY
from the SCENEs A selection of stories from C&EN’s six online TOPICAL NEWS CHANNELS O
NATURAL PRODUCT FERRIES ANTIBIOTIC INTO BACTERIA Chemists struggle to develop antibiotics for gram-negative bacteria such as Escherichia coli because, in part, the microbes have a second cell membrane outside their cell walls that can deflect drug molecules. Many researchers have tried to use siderophores—molecules made by bacteria to scavenge for iron in the environment—to carry cargo into the cells, says Elizabeth M. Nolan of Massachusetts Institute of Technology, but they’ve had limited suc-
O OH cess. Now, Nolan and her team report N N 3 H that they have successfully N N OH O Linker linked β-lactam antibiotics to NH a siderophore called enteroNH O bactin, allowing the drugs to O O slip into and selectively kill HN O O O E. coli (J. Am. Chem. Soc. 2014, O O DOI: 10.1021/ja503911p). The reH O N OH HN searchers attached enterobactin to S N H O HO ampicillin or amoxicillin and then O HO CO2H looked at the activity of the compounds against various strains of Ampicillin Enterobactin E. coli under low-iron conditions. All of the strains were more susceptible to infects the urinary tract, called CFT073, the antibiotic-siderophore conjugates than the new compounds were 1,000 times as to the unlinked drugs. For one strain that potent as the unlinked ones.
J. AM. CHEM. SOC.
FROM THE BIOLOGICAL SCENE
FROM THE MATERIALS SCENE
SILICON CLAWS CAPTURE SINGLE CELLS Using techniques developed by computer chip manufacturers, scientists have created tiny silicon claws that can grasp and hold individual living cells for analysis (Nano Lett. 2014, DOI: 10.1021/nl500136a). David H. Gracias, a biomolecular engineer at Johns Hopkins University, and his team think the grippers could collect cells of interest in the bloodstreams of patients. Each silicon oxide gripper consists of three or four arms extending off a square where a cell could sit. At the base of each 10- to 70-µm-long arm sits a hinge consisting of thin layers of silicon oxide and silicon dioxide. Stress between the two layers causes the hinges to bend, drawing the arms closed. The team made an array of grippers on a silicon chip and held them open by depositing the arms and hinges on top of a copper layer. When the researchers pipetted
Cross-shaped silicon grippers remain open while attached to a silicon substrate (top) and close after time in water, capturing single red blood cells (bottom).
a liquid culture of mouse cancer cells on the chip, the water dissolved away the copper, and the arms closed around single cells. Gracias hopes to add other functions to the claws, such as attaching antibodies to the arms to target specific cells.
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JULY 14, 2014
FRO M THE NANO SCENE
FULL-COLOR PRINTING WITH ALUMINUM NANOSTRUCTURES Plasmonic printing is a recently developed method to create color images using different shapes and sizes of gold or silver nanostructures. It relies on the oscillations of electrons in the metal surfaces and can produce images with a resolution 100 times as high as that of a common desktop printer. Now, researchers have expanded the color palette of the technique using tiny aluminum-capped nanopillars (Nano Lett. 2014, DOI: 10.1021/nl501460x). A team led by Joel K. W. Yang of the Agency for Science, Technology & Research, in Singapore, and the Singapore University of Technology & Design, used electron beam lithography to make 95-nm-tall pillars of hydrogen silsesquioxane on a silicon substrate. They then capped each pillar with a 20-nm-thick layer of aluminum. Each pixel consists of four nanopillars; tuning the diameters and arrangement of the pillars produced a palette of more than 300 different colors. By avoiding dyes or pigments, this printing technology produces images that are resistant to fading, Yang says. The aluminum pixels remained stable throughout a seven-month period, unlike the previous silver pixels, which oxidized and degraded within a week.
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