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Originally published January, 1998

IVD Technology News

Sensors promise handheld analysis

A new technology developed at the University of Washington promises diagnostic tests with shirt-pocket portability and immediate results.

Sinclair Yee, PhD, and colleagues at UW (Seattle) have developed a light sensor that combines circuitry for spectral analysis with a kind of biochemical paint attached to the end of a probe. When dipped in a patient sample, such as blood, the paint draws target molecules into the light. "The sensor could be the size of a pencil," says Yee, a professor of electrical engineering.

Prototype of UW's surface plasmon resonance probe. Photo Courtesy Sinclair Yee

The electronics for the probes, which will both detect the presence and measure the concentration of specific chemicals, has been licensed to start-up company Ikonos Corp. (Portland, OR). Using proprietary biochemistry, Ikonos is developing an array of sensors. "We plan to bring the lab to the patient in the shirt pocket of the doctor," says Christophe Sevrain, company president.

The compact size of the technology means the probe is brought to the specimen, not the other way around. ER physicians and paramedics might immerse it in a patient fluid sample to test for the bacteria that cause salmonella poisoning, for example, or the enzymes associated with a heart attack.

"Imagine putting modules into a calculator-sized instrument," Sevrain says. "One could be for blood analysis. Another could be for urine analysis. They would both use Dr. Yee's technology, but the different modules would have our molecular imprinting chemistry. It's a good combination of two different technologies."

Chemical agents on the surface of the probe attract and bond target molecules. White light is selectively absorbed by the target chemicals, if they are present. The absorbed wavelength of light, called the wavelength of resonance, indicates the composition of the sample to a concentration of 10 parts per billion.

The basic technology, called surface plasmon resonance, has been around for about 15 years. The problem has been reducing its size and cost—about that of a console television priced at more than $200,000—so that a practical instrument could be made. The UW researchers have achieved that dual goal by harnessing planar geometry, which has shrunk the probe and associated processor to the size of a calculator with a likely price of less than $2000.

The probe, which is shaped like an orchestra conductor's baton, contains a glass-fiber core less than half a millimeter in diameter with planar electronics built around it. "All the integrated circuits are built along a plane," Yee notes.

The device developed at UW illuminates the sample with two beams of light. One scans for the target chemical. The other serves as a reference to record changes in the sample, such as changes of temperature, that might affect measurements. Subtracting the two signals ensures accurate results.

The technology is still in the prototype stage, but that could soon change. Sevrain expects that Ikonos will begin manufacturing a product incorporating the UW electronics and its own proprietary biochemistry by the end of this year.—Greg Freiherr