NOVEMBER 3, 2010
What A Cell Wants — Chemically Speaking
Microfluidics: A novel microfluidic device probes bacterial movement along chemical gradients
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BIOLOGY IN MOTION Bacterial cells swim up or down chemical concentration gradients
In classic cartoons, characters drift along wafting scent trails toward freshly baked pies. Similarly, through a process called chemotaxis, bacteria navigate chemical concentration gradients in search of food and friends, and away from poisons and predators.
Chemotaxis represents a classic example of how cells respond to their environments. Researchers have studied it for years, most recently, by watching cells swim through microfluidic devices toward chemicals that attract them. Now Kim Taesung and Kim Minseok of Ulsan National Institute of Science and Technology, in South Korea, have upped the ante, developing a chip to probe chemotaxis along six concentration gradients simultaneously (Anal. Chem., DOI: 10.1021/ac102022q).
Built of a soft polymer called poly(dimethylsiloxane), Kim and Kim's device resembles a bicycle wheel with six 8-mm-long channels forming the spokes. Reservoirs sit at the center of the wheel and at the end of each spoke. Connecting the radial reservoirs and the spokes are plugs made of agarose gel, which allow potential attractants to diffuse into the channel without "convection" — that is, without generating liquid flows that could push cells around. By loading a chemical into each of the radial reservoirs, and none in the central reservoir, the researchers can produce six stable, linear concentration gradients over a longer distance than any formed in previous device designs, according to the researchers.
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Read more here/Leia mais aqui: Chemical and Engineering News
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Diffusion-Based and Long-Range Concentration Gradients of Multiple Chemicals for Bacterial Chemotaxis Assays
Minseok Kim† and Taesung Kim*†‡
School of Mechanical and Advanced Materials Engineering and School of Nano-Bioscience and Chemical Engineering, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Ulsan 689-798, Korea
Anal. Chem., Article ASAP
DOI: 10.1021/ac102022q
Publication Date (Web): October 27, 2010
Copyright © 2010 American Chemical Society
* Corresponding author. E-mail: tskim@unist.ac.kr. Tel: +82-52-217-2313. Fax: +82-52-217-2509., †
School of Mechanical and Advanced Materials Engineering. , ‡
School of Nano-biotechnology and Chemical Engineering.
Abstract
We present a diffusion-driven and long-range concentration gradient generator that uses hydrogel as a porous membrane to prevent convection flows but allow the diffusion of cell signaling molecules for the study of bacterial chemotaxis in a microfluidic device. Using this device, we characterized the critical concentrations associated with the chemotactic responses of cells that initially created a population band and then migrated in bands in the presence of multiconcentration gradients. In addition, this device can be used to study the preferential chemotaxis of bacterial cells toward different carbon sources: glucose, galactose, and mannose were preferred over arabinose and xylose, in this order. This was possible since the device is able to simultaneously produce long-range concentration gradients of different chemicals as well. The method presented in this study is easy to perform and the device is cheap to fabricate, so that we believe that these characteristics not only make this device a very useful tool to study the chemotaxis of various, motile microorganisms but also permit parallel experimentation and reduce the time and effort needed in characterizing bacterial responses to various chemicals.
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