UW Sensors Take Chemical Analysis Out Of Lab And Into The Field

August 29, 1997

Doctors needing chemical analyses such as blood tests to make life-saving diagnosis and treatment decisions soon won't have to lose precious time waiting for results to come back from the lab. New hand-held sensor technology developed at the University of Washington will allow physicians to bring a sophisticated "laboratory" directly to their patients for instant, on-site chemical analysis.

Based on an emerging technique called surface plasmon resonance pioneered at the UW College of Engineering, the new sensors bounce light off a sample and use the reflection of the incoming light to determine the presence and concentration of specific chemicals. In addition to medical tests, the sensors can be used for detecting air and water pollution, food poisoning, explosives and a variety of other chemical agents.

"Surface plasmon resonance sensors have been used for approximately 15 years in research labs, but the technology was too complicated, cumbersome and expensive for other applications," explains Sinclair Yee, professor of electrical engineering and principal investigator on the project. "The potential benefits for using these sensors in areas such as medicine, environmental monitoring and manufacturing are tremendous, so we set out to develop an instrument that is portable and inexpensive."

The UW technology shrinks the size of a surface plasmon resonance sensor system from that of a console television set to a laptop computer and reduces the cost from $200,000 to under $2,000. The UW has patented the technology and licensed it to international instrument-maker Biacore and to Ikonos Corp., a Portland-based start-up company.

The key breakthrough made by Yee and his research team was to develop a hand-held probe enabling the sensor technology to be placed into a fluid sample rather than the sample being put into a laboratory machine for chemical analysis.

The UW probe, resembling an orchestra conductor's baton, contains a glass fiber core less than half a millimeter in diameter. White light (containing all colors in the spectrum) is transmitted down the fiber core to the tip of the probe where the sensor surface is in contact with the fluid sample. The color, or wavelength, at which most of the light is absorbed into the sample rather than reflected back up the probe is called the wavelength of resonance and depends on the chemical composition of the sample, Yee explains. Computer analysis of the reflected light, therefore, can determine the presence and concentration of specific chemicals.

To ensure that particular chemicals are detected if they are, in fact, present in the sample, a layer of chemical binding agents is applied to the sensor surface to attract and bond molecules of the target chemical. A coating of salmonella antibodies on the sensor surface, for example, will bind salmonella bacteria if they are present in a sample, according to Clement Furlong, UW professor of medical genetics. Furlong and chemistry Professor Charles Campbell are developing various chemical binding agents for use in surface plasmon resonance sensor systems.

With the UW technology, these systems are sensitive enough to detect lead, arsenic and copper in concentrations as small as 10 parts per billion, making it ideal for monitoring soil and water pollution, the researchers say. The sensors also may be used for real-time monitoring of chemicals, microorganisms and viruses in marine environments.

One of many potential medical applications is field-based blood tests enabling early detection and treatment of heart attacks. To determine if a patient is having a heart attack, Furlong explains, doctors need to know whether the patient's blood contains certain cardiac enzymes indicating a breakdown of the heart muscle.

"Paramedics or emergency room doctors want to know right away whether a patient is having a heart attack and can be given clotting factor medication because there is significant risk and expense involved," he says. "As recently as the early 1980s, cardiac enzyme blood tests took eight hours, and they still take longer than they should because they go back and forth to a lab. Our sensor technology could be in every emergency room and ambulance so medical professionals would have instant, on-site bloodwork results."

For manufacturing, the new sensors can be used to measure everything from the sugar content of wine to dosage levels in drugs and contamination in food. The latest UW technology is ideal for continuous monitoring of manufacturing processes to ensure quality control, according to Yee. It employs two light beams: one for detecting the resence and concentration of the target chemicals and the other to monitor fluctuations in the system as well as other changes, such as the temperature of the sample, that might affect results.

Using this latest UW technology, Ikonos Corp. is developing prototype sensors to be evaluated by a dozen Fortune 500 companies. Ikonos President Christophe Sevrain says he hopes to start manufacturing the instruments by the end of next year. Potential buyers range from major petrochemical processors and drug manufacturers to police departments and veterinary clinics, he says.

"This is a revolution in sensor instrumentation much like the revolution in computer technology," Sevrain says. "Just as computers that used to be huge, prohibitively expensive and accessible to only a few people have become portable and commonplace, the UW sensor technology enables us to put sophisticated chemical analysis capabilities, previously available only at laboratories, in the hands of many, many more people."


University of Washington

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