University team shares grant from NASA for biosensor research

Two teams of local researchers — from Princeton, Rutgers University and Drexel University in Philadelphia — will receive during the next three years a combined $1.8 million from NASA for research applicable to space exploration.

Princeton chemical engineering professors Ihan Aksay and Jeffrey Carbeck, Princeton graduate student Chris Martin, Jessica Jarvis '01 and two Drexel physicists compose one research team. With a $1.3-million grant, the group is constructing and refining experimental biological sensors.

Rutgers professor Michael Gershenson leads the second team, which is receiving $500,000 from NASA. His team is developing more advanced bolometers, which are instruments used to detect deep-space electromagnetic radiation. NASA may use these instruments to increase understanding of how star systems form.

According to Aksay, the Princeton-based project evolved last year when his group was working to identify the types of biological species that live in water and in air, including those that live in the human body.

Aksay said members of his group realized that once they could identify biological presences with a small device, they could construct a sensor that would be implanted in the body. This sensor would then relay information about those biological presences — such as specific molecules or viruses — to an outside monitor.

Carbeck said the possibility of long-distance monitoring of the human body's inner environment piqued NASA's interest because it would allow astronauts' health to be examined more closely while they were in space.

Describing the sensor's construction and function, Aksay said a cantilever — a projecting support anchored by one side — would offer binding sites for the specific biological product being monitored. When molecules bind to proteins embedded in the cantilever's surface, they cause an electric signal to be sent back from the sensor to a monitor.

"Visualize a diving board like in the Olympics," Aksay said. He explained that the cantilevers in his team's sensors would not bend, but would vibrate with a certain resonance frequency.

Returning to the diving board comparison, he said, "The resonance frequency depends on the weight on the diving board. We propose to make a diving board 100 times smaller than [the diameter of] a human hair and measure the resonance frequency when something binds to it."

Carbeck said his team has a strategy for using the devices in a laboratory setting, but he believes challenges would arise if the sensors were implanted in a living system. He noted, however, that the step is probably beyond the scope of the current project.

Aksay's team now is grappling with the problem of boosting the sensors' sensitivity.

Aksay said with their present technology, the scientists can increase the surface area where biological molecules can bond to the sensor, thus increasing its sensitivity. With the addition of a microscopically thin, porous gel coat, Aksay said the total surface area of the cantilever becomes about 1,000 square meters.

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Jarvis is basing her senior thesis on the viability of using such a gel coat to boost sensor sensitivity. She and the other members of the team said the group will continue to refine its techniques and materials with the three-year grant from NASA.

"Making [the cantilevers] is a long project, so we are focusing on the fundamental issues," Aksay said.