January 27, 2005
Project yields tiny sensor with a veritable sea of possible uses
It began as a modest proposal by three UW professors — geneticist Clement Furlong, electrical engineer Sinclair Yee and chemist Lloyd Burgess. In 1994, the three scholars approached Washington Sea Grant Program, seeking funds to explore two different sensor technologies with, in their words, “broad application for marine analyses.”
Little could WSGP’s research proposal review panel or, for that matter, Furlong, Yee or Burgess have envisioned how truly widespread that application would be. After 10 years of refinement, one of these sensors, the surface plasmon resonance (or SPR) biosensor system, has been tested in an array of environments on land, in seawater and in the sky.
Working in collaboration with the Dallas-based Texas Instruments, the research team has developed a device that can detect the chemical remnants of agricultural pesticides, identify toxic metabolites such as domoic acid, the chemical culprit behind amnesic shellfish poisoning, or give an important early warning, should the faintest traces of sarin gas or other lethal weapons in the terrorist’s arsenal be found.
The equipment can detect protein toxin concentrations of 2.8 parts per trillion, domoic acid at 100 parts per billion and cortisol (the hormone synthesized and released by the adrenal glands) at 271 parts per trillion, according to Furlong. To put this in perspective, one part per trillion is the equivalent of a pinch of salt in 10,000 tons of potato chips or one inch in 16 million miles.
Even smaller infectious agents, including viruses, microbes and spores such as anthrax, will soon be detectable by the SPR system, Furlong notes. Whether used in disease diagnosis or for homeland security, the many benefits of such improved efficiency are truly staggering.
An inch-long chunk of black plastic houses all of the microelectrical components of the SPR sensor element. Each sensor system contains banks of these deceptively simple looking elements all wired to the main processing software. Each measures changes in the refractive index (or RI) on the sensor’s gold surface. If the target agent domoic acid, for example, is present in the sample, it will displace antibodies attached to the sensor’s gold-plated surface. This causes the RI to decrease. Larger analytes, such as toxic proteins, viruses and whole microbes, produce an increase in the RI when they bind to specific antibodies immobilized on the gold surface of the sensor. The change in the RI is converted to an electronic signal, which can then be analyzed by sensor software.
With the antibodies firmly in place, each sensor will continue to function flawlessly, on a laboratory bench or in the field, even after several months of use. By using several biosensors simultaneously, the system can scan for multiple contaminants at the same time.
“The earliest commercial versions of the SPR sensor system were the size of large TV sets,” says Furlong. The most recent piece has shrunk considerably: one 24-channel prototype is the size of a small lunchbox, ideal for gathering data in the field. It features touch-screen controls and a waterproof case — enhancements that make sample analyses even easier than before. Another SPR prototype has been mounted in a small experimental aircraft, capturing information about foreign molecules in the atmosphere.
The biosensor elements have also been miniaturized. What once resembled a packet of dental floss is now the size of a dime, allowing for further size reductions in the instrumentation.
“Before we created our device, measurements were made with cumbersome gear, whose price tags — upwards of $200,000—made field research fairly unfeasible” offers Furlong. “The new technology is both portable and affordable — about a tenth of the price of older lab instruments,” he says.
In the Electrical Engineering laboratory of Tim Chinowsky, half hidden by plastic toolboxes and coils of electrical wire, sit several new biosensor systems in-the-making. One of these is a freestanding unit, created for making unattended assessments of the environment at hazardous sites. “In a battle zone, one of these portable units could sniff the molecular signatures of buried explosives, such as land mines, or warn of the presence of chemical weapons” Chinowsky explains.
Applications such as these have attracted the interest of the U.S. Defense Department, which recently met with Chinowsky, a former Sea Grant Industry Fellow, now a UW research assistant professor of Electrical Engineering, and others from Furlong’s research team.
In June 2004, the UW licensed the rights to the SPR technology to Seattle Sensor Systems, a local startup company founded by Furlong, Yee, Chinowsky, research scientist Scott Soelberg and Alexei Naimushin, formerly with the Department of Genome Sciences and the Department of Medicine. As President of the Seattle firm, Naimushin brings over 13 years of experience in design of scientific instruments, including four years in design and development of SPR sensors and applications. He and Furlong met during Naimushin’s doctoral review process at the UW.
“The SPR sensor is a prime example of applied technology,” says Nanushin. “It grew out of UW research and has real application, not in the distant future but in my lifetime.”
“It’s been exciting to work on a collaborative effort, with all the extremely talented members of multi-disciplinary team,” says Furlong. “We’ve benefited from assistance from Texas Instruments, the Department of Defense, the UW’s Center for Process Analytical Chemistry and many other partners. However, I’m especially grateful for the support of Washington Sea Grant Program, which has helped us from the earliest phases of our research.”
