Chip gauges cell reactions

By Eric Smalley, Technology Research News

Biological cells react quickly and distinctly to many types of stimuli, including antibiotics, radiation, pathogens, and chemicals.

Researchers from the State University of New York at Buffalo have devised a way to test within minutes the reactions of cells to all types of stimuli. The researchers' system is very sensitive, relatively inexpensive, uses little power, and is portable.

Key to the technique is the connection between a cell's volume and its environment.

The method could eventually be used to screen cells and portions of cells to evaluate their reactions to stresses like radiation and chemicals, said Frederick Sachs, a professor of physiology and biophysics at the State University of New York at Buffalo. It could gauge, for example, the effectiveness of chemotherapy or radiation protocols on human cancer cells, he said.

The silicon chip sensor measures electrical resistance. Cells are electrical insulators, while saltwater conducts electricity. When cells are put in a container of saltwater they displace some of the water, increasing the resistance within the container. A cell tends to swell in the presence of a toxin, displacing more of the saltwater, which measurably increases the container's electrical resistance.

Lab devices that measure cell volume exist, but are larger and slower than the researchers' microfluidic device.

The researchers' prototype is a silicon wafer with a 1.5-millimeter-wide, 15-micron-deep channel that connects a pair of chambers. One chamber is the same depth as the channel; the other is 55 microns. Each chamber contains four platinum electrodes that measure electrical resistance. The shallow chamber measures cell volume and the deeper chamber calibrates the device by measuring the electrical resistance of the fluid.

The technique is faster and simpler than microfluidic devices that measure cell growth, and it provides direct observation of changes to cells, said Sachs. It can be used to measure cells and parts of cells like organelles and lipid vesicles, he said.

The prototype allowed the researchers to assess the sensitivity of different strains of E. coli bacteria to antibiotics within ten minutes at room temperature, said Sachs. "It is rare that we come up with something so general and so simple that is still useful," he said. "But simplicity is critical for reliable assays."

The method could be adapted to screen many samples at once by automating the fluid handling and temperature control and adding robotics to automate the process, said Sachs.

The sensor could be used practically in one to five years, said Sachs. The next steps are to simplify sample placement and to automate fluid and temperature control, he said. The technology must also be implemented in plastic and interfaced with robotics to adapt it for commercial high-throughput use, he added.

Sachs's research colleagues were Daniel A. Ateya, Philip A. Gottlieb, Steve Besch, and Susan Z. Hua. The work appeared in the January 22, 2005 issue of Analytical Chemistry. The research was funded by the National Institutes of Health (NIH) and the National Science Foundation (NSF).

Timeline:   1-5 years
Funding:   Government
TRN Categories:   Microfluidics; Biotechnology; Sensors
Story Type:   News
Related Elements:  Technical paper, "Volume Cytometry: Microfluidics Sensor for High-Throughput Screening in Real-time," Analytical Chemistry, January 22, 2005


May 4/11, 2005

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