College of LAS « Illinois

Chemical and Biomolecular Engineering

Implants Could Monitor Glucose Levels 24/7

Michael Strano

It looks like a simple watch. However, this watch would regularly beam near-infrared light to a nano-sized sensor implanted under your skin. The sensor radiates fluorescent light back, transmitting information about levels of glucose and cholesterol in your body.

An LAS research team, led by Michael Strano, has laid the groundwork for making such a sensor possible.

Strano, a professor of chemical and biomolecular engineering, recently showed that a "carbon nanotube" biosensor was capable of measuring glucose levels—the blood sugar levels that an estimated 18 million diabetics in the United States must regularly monitor.

At present, most diabetic patients must prick their finger every few hours to check glucose levels in the blood.  A goal in the biosensor community, Strano says, is to replace this system with sensors that can check glucose levels continuously in real-time instead of just a few times a day. LAS researchers have taken one of the first steps in the development of sensors that can do just that.

A carbon nanotube is a rolled-up layer of graphite so tiny that its diameter is roughly the size of two water molecules. Carbon nanotubes are uniquely suited to the biosensor task, Strano explains, because they resist degradation and emit fluorescent light when hit with near-infrared light.

His team coated a carbon nanotube with the enzyme glucose oxidase, which causes glucose to bind to the structure, triggering a string of chemical reactions that affect the nanotube's fluorescence. The more glucose that is present, the brighter the nanotube will emit fluorescent light.

According to Strano, many hurdles lie ahead, such as testing the body's immune reaction to implanted sensors. But if nano-scale biosensors become a reality years down the line, they could be implanted with an outpatient procedure, rather than requiring surgery like other sensors being explored.  A single carbon nanotube sensor could even be developed to monitor all kinds of important molecules in the blood—not just glucose.

"With these biosensors, it would be the equivalent of getting a complete blood workup in real time," he says. "Imagine that your doctor could download, from a PDA, your complete six-month history of glucose, cholesterol, and a wide range of other important biochemicals present in the blood. Ultimately, we think this will transform medicine."

Fall/Winter 2005–06