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Therrien Strives to Perfect a System for Detecting Bacteria

Existing Methods Lack Either Speed or Sensitivity

Joel Therrien

04/19/2006
By For more information, contact media@uml.edu or 978-934-3224

There are two basic methods of detecting the presence of bacteria, according to Asst. Prof. Joel Therrien. One, he says, is very sensitive but too slow. The other is very fast but not sensitive enough.

Therrien, who joined the Electrical and Computer Engineering Department last fall, is conducting research to perfect a biosensor that will be both fast and sensitive. Such a sensor would have applications in many areas, but especially in medicine and national defense.

And way, way out in the future, Therrien’s biosensor ߝ which, he says, could be as small as a box of Tic Tacs ߝ might be used by shoppers to check cuts of meat in the supermarket to make sure they are free of bacteria.

One method for detecting bacteria in medical practice today involves the collection of samples that are then grown in a Petri dish for 12 to 24 hours. Meanwhile, the patients in question must be treated on the assumption that they are, in fact, infected with the bacteria.

The second method entails testing for airborne bacteria, such as anthrax. This process, in which the air passes through equipment about the size of a shoebox, is fast but not extremely sensitive.

“The goal,” says Therrien, “is to develop something that is highly sensitive but that can do the job in real time.”

He’s researching a system that involves measuring the vibrating frequency of nano-sized cantilevers (think diving boards). Bacteria have properties that cause them to stick to specific proteins in the body. Therrien would coat his cantilevers with proteins that would capture and indicate the presence of various types of bacteria.
The trick is to be able to detect vibrations on the infinitesimally small cantilever.

“The smaller the cantilever, the more sensitive it is,” he says. “My technique is to use a method called Tunnel Gap Modulation Spectroscopy that I developed while doing post-doctoral work at Purdue University.”

The objective is to make this system small enough and inexpensive enough to be practical. To accomplish this, Therrien’s idea is to mount nano-tube cantilever sensors on chips that will be able to detect different kinds of bacteria.

“Ideally, these chips would cost only a few dollars apiece and would be contained in something as small as a Tic Tac box.,” he says.