SCIENCE & TECHNOLOGY
from the SCENEs FROM THE BIOLOGICAL SCENE
MICROFLUIDIC DEVICE MIXES AND MATCHES DNA
ACS APPL. MATER. INTERFACES
A new microfluidic device could help synthetic biologists engineer new microorganisms by building many DNA plasmids at a time and delivering them into bacteria or yeast (ACS Synth. Biol. 2015, DOI: 10.1021/ acssynbio.5b00062). The device contains interconnecting pathways made from electrode “bricks.” By applying a voltage pulse to one brick after another, the researchers can move droplets along the pathways. To
make plasmids, the device draws droplets from different reservoirs of DNA pieces, mixes them, and incubates the mixture to allow the DNA pieces to join together. Steve C. C. Shih and Anup K. Singh of Sandia National Laboratories, in Livermore, Calif., and the Joint BioEnergy InstiA microfluidic chip can build many combinations tute used the device to build 16 difof DNA plasmids and insert them into cells. ferent plasmids—all possible pairs of four genes and four promoters, which serve as on-off switches for gene had the correct sequences. Shih is develexpression—and transfected them into oping a three-dimensional microfluidic bacteria or yeast. Subsequent tests showed device to increase the number of different that 95% or more of the plasmids created plasmids produced in a single batch.
FROM THE NANO SCENE
BRIGHT NANOPARTICLE FIBERS SHOW OFF STRUCTURAL COLOR Fibers spun from latex nanoparticles can achieve bright colors without the use of dyes (ACS Appl. Mater. Interfaces 2015, DOI: 10.1021/acsami.5b03289). Instead, they derive color like certain bird feathers and beetle shells do—by interaction between light and the physical structures created by the particles. Ke-Qin Zhang of Soochow University, in China, and colleagues wanted to apply this phenomenon— known as structural color—to produce textile colors that didn’t fade or lead to environmentally harmful waste. The team synthesized poly(styrenemethyl methacrylate-acrylic acid) nanospheres and dispersed them in a polyvinyl alcohol solution. Using electrospinning, the researchers made mats of 1.3-µm-diameter fibers. The packed spheres in each fiber form a crystal that reflects a narrow range of wavelengths, creating a nearly pure
A scanning electron micrograph shows a fiber made by electrospinning a dispersion of latex nanospheres (top). Different sizes of spheres in the fibers create different colors (bottom).
color. By controlling the size of the nanoparticles, researchers can tune the colors. The fibers aren’t strong enough to be woven into textiles, Zhang says, but his team is exploring ways to overcome that problem.
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26
JULY 13, 2015
FROM THE MATERIALS SCENE
CONTACT LENS COATING COULD FIGHT EYE INFECTIONS A simple one-step process coats contact lenses with an invisible antimicrobial film (Biomacromolecules 2015, DOI: 10.1021/acs. biomac.5b00359). The coating could cut the risk of eye irritation and infections in the 140 million contact lens wearers worldwide. Yi Yan Yang of the Institute of Bioengineering & Nanotechnology, in Singapore; James L. Hedrick of the IBM Almaden Research Center, in San Jose, Calif.; and their colleagues used four different ingredients to make the coating: branched polyethylenimine (bPEI), catechol, polyethylene glycol (PEG), and hydrophobic urea. The bPEI acts as a polymer scaffold for the other components, catechol helps the resulting coating stick to the lens surface, PEG suppresses the adhesion of microorganisms and proteins, and hydrophobic urea groups help the polymer disrupt cell membranes. The researchers dipped a cleaned contact lens into the coating and then sterilized it. The coating kept various bacteria and fungi from growing on the lens surface for seven days and was not toxic to cultured human cornea cells when tested over a 24-hour period. The coating method could be easily integrated into current lens manufacturing processes, Yang says.
ACS SYNTH. BIOL.
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