Innovative Sensor Could Offer New Biomedical Applications

Originally Published MDDI April 2002

R&D DIGEST

Government and university researchers have collaborated on development of a new fluorescence-based chemical sensor that could be applied to point-of-care medical testing, high-throughput drug discovery, and detection of pathogens, among other applications. Developed by scientists at the U.S. Department of Energy's Ames Laboratory (Ames, IA) and the University of Michigan, Ann Arbor, the compact sensor can be used to monitor oxygen, inorganic gases, biochemical compounds, and biological organisms.

The sensor technology is based on research by Joseph Shinar, PhD, senior physicist at Ames, and colleagues to study the photophysics of luminescent organic thin films and organic light-emitting devices (OLEDs). OLEDs luminesce when a voltage is applied. Research at the University of Michigan, led by Raoul Kopelman, PhD, professor of chemistry, was focused on developing fluorescence-based sensors. Collaboration between the two groups led to development of an integrated OLED/optical chemical sensor.

Says Shinar, "Integration and miniaturization of fluorescence-based chemical sensors is highly desirable, as it is the first step towards the development of fluorescence-based sensor arrays that could be used for analysis of living cells and organisms, and biochemical compounds." According to the researcher, fluorescence-based chemical sensing devices typically include a sensing element that produces the fluorescence, a light source to excite the sensing element, and a photodetector that responds to the fluorescence of the sensor.

Conventional sensors use lasers or inorganic light-emitting devices as light sources. Such sensing devices can be expensive and bulky, and cannot be integrated with the other sensor components.

A key advantage of the OLED/optical chemical sensor, on the other hand, is the integration of the detector and the OLED light source that excites the fluorescence. Says Shinar, "This is a real advantage. With this kind of geometry, called 'back detection,' we should be able to use the sensor for in vivo biological applications."

Describing the back-detection design, Shinar explains that the sensor "is in contact with the biological solution on the substrate, and your OLED light source is behind the substrate." Shinar says, "It's like a sandwich: sample solution, sensor, substrate, OLED. As the OLED light source excites the sensor, the sensor fluoresces. When the sensor detects the compound of interest in the sample solution, its fluorescence changes, and the change is picked up by a photodetector positioned behind the OLED light source."

Last year the researchers demonstrated an oxygen-sensor prototype in which the OLED was integrated with the oxygen-sensor film. According to Shinar, front detection was used instead of back detection with the oxygen-sensor prototype.

Shinar also believes that the collaborators will be able to develop a prototype for a glucose sensor in the near future. "The recipe is there, but we're wrestling with the stability of the glucose enzyme, which has a drastic effect on the uptake of oxygen by glucose," he says.

Photo courtesy of DOE/Ames Laboratory

Copyright ©2002 Medical Device & Diagnostic Industry