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Carbon nanotube 'tattoo' to measure blood glucose levels in diabetics

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June 10, 2010

Glucose molecules such as this can cause serious problems for diabetes sufferers

Glucose molecules such as this can cause serious problems for diabetes sufferers

Diabetes is an enormous global problem... and it is on the rise. Despite decades of research and advances in technology, the methods of accurately measuring glucose in the body are still quite primitive. A new type of blood glucose monitor being developed at MIT could not only eliminate the need for finger pricks, but could also offer more accurate readings by way of a “tattoo” of nanoparticles injected below the skin.

A 2008 study in the New England Journal of Medicine showed that continuous monitoring helped adult type I diabetes patients who were at least 25 years old better control their blood glucose levels. However, existing wearable devices are not as accurate as the finger-prick test and have to be recalibrated once or twice a day - a process that still involves pricking the finger.

Most existing continuous glucose sensors work via an injection of an enzyme called glucose oxidase, which breaks down glucose. An electrode placed on the skin interacts with a by-product of that reaction, hydrogen peroxide, allowing glucose levels to be indirectly measured. However, none of those sensors have been approved for use longer than seven days at a time.

The technology behind the new sensor being developed by Paul Barone, a postdoctoral researcher in the MIT Department of Chemical Engineering, and professor Michael Strano, is fundamentally different from existing sensors according to Strano. It is based on carbon nanotubes wrapped in a polymer that is sensitive to glucose concentrations. When this sensor encounters glucose, the nanotubes fluoresce, which can be detected by shining near-infrared light on them. Measuring the amount of fluorescence reveals the concentration of glucose.

The researchers plan to create an “ink” of these nanoparticles suspended in a saline solution that could be injected under the skin like a tattoo. A device similar to a wristwatch would be worn over the tattoo and shine near-infrared light on it. The device would detect the resulting fluorescence and display the patient’s glucose levels. The “tattoo” would last for a specified length of time, probably six months, before needing to be refreshed.

One advantage of this type of sensor is that, unlike some fluorescent molecules, carbon nanotubes aren’t destroyed by light exposure. “You can shine the light as long as you want, and the intensity won’t change,” says Barone. Because of this, the sensor can give continuous readings.

“The most problematic consequences of diabetes result from relatively short excursions of a person’s blood sugar outside of the normal physiological range, following meals, for example,” says Strano. “If we can detect and prevent these excursions, we can go a long way toward reducing the devastating impact of this disease.”

Barone and Strano are now working to improve the accuracy of their sensor. Any glucose monitor must pass a test known as the Clarke Error Grid, the gold standard for glucose-sensor accuracy. The test, which compares sensor results to results from a lab-based glucose meter, needs to be very stringent, since mistakes in glucose detection can be fatal.

Barone says they are still years away from human trials of the technology, but that trials on animals may start soon.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
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