Short-term Bio Sensors Monitor From Afar

"We were asked to develop micro sensors for metabolic monitoring oftroops," says Dr. Michael Pishko, professor of chemical engineering andmaterials science and engineering. "These implantable sensors areintended to monitor the physiology of troops in the field."

By monitoring glucose, oxygen, lactose and pyruvate, the U.S. Armyhopes to be able to assess the metabolic health of troops in the fieldand improve the response to the injured.

The researchers, who include Pishko, Dr. Amos M. Mugweru, postdoctoralresearcher, and Becky Clark, graduate student in chemical engineering,designed an implantable glucose sensor of glucose oxidase molecules --the enzyme that reacts to glucose -- immobilized in photopolymerizedand microlithographically patterned film. The polymer exchangeselectrons with the glucose oxide to produce a current, which is thesignal that can be monitored from afar.

"We cannot make the sensors too small, because they need to be bigenough to handle and sturdy enough to be inserted without bending orbreaking," says Pishko. "We do want to have two to four sensors perindicator so that the signal is verifiable and viable even if onesensor fails."

Sensors could be bundled in groups depending on the metabolite to be monitored.

"The enzymes entrapped in these polymer films and containingbiocompatible hydrogels show good stability and sensitivity," theresearchers told attendees today (Aug. 31) at the 230th AmericanChemical Society National Meeting in Washington, D.C.

The military is interested in monitoring glucose, pyruvate, lactate andoxygen for an overall metabolic picture, so four separate sets ofsensors would be necessary, each individually addressable. Personnel ina distant base camp could monitor the soldiers' health and relayinformation into the field. These metabolic readings would also helpmedics decide who to treat first and assess the severity of injuries.

Individual sensors also have their place. The researchers are workingwith the Juvenile Diabetes Foundation on glucose sensors. Exercisephysiologists would like to be able to monitor lactate as a measure ofhow hard muscles are working. Pediatricians would also like to be ableto monitor the functions of the tiniest of newborns.

Because these sensors would be implantable and temporary, one day,marathon runners might need not only to pin on their numbers, but alsoto receive their implantable metabolic sensor array before approachingthe starting line.

"The body is hostile to this kind of implant and the sensors willeventually wear out," says Pishko. "For these applications, the sensorsonly need to work for a short period of time. Even for the soldiers, 24to 72 hours is sufficient."

The U.S. Army funded this research.