Nano Ink 'Tattoo' Could Monitor Diabetes

Controlling your diabetes could make you look tough.

A special tattoo ink that changes color based on glucose levels inside the skin is under development by Massachusetts-based Draper Laboratories. The injectable nanotech ink could eventually free diabetics from painful blood glucose tests.

"It doesn't have to be a large, over-the-shoulder kind of tattoo," said Heather Clark, a scientist at Draper. "It would only have to be a few millimeters in size and wouldn't have to go as deep as a normal tattoo."

Clark and her colleagues didn't set out to create a glucose-detecting ink.

"At first I didn't even think it was possible," said Clark.

Originally the scientists developed a sodium-sensitive ink to monitor heart health, advancing basic knowledge of electrolytes in the body, or to ensure athletes are properly hydrated.

Monitoring a single ion is easier than a complex molecule made of 24 atoms however. After speaking with a colleague, Clark decided to give glucose detection a try.

She started with the basic three-part system to detect sodium and modified to detect glucose. The nano ink particles are tiny, squishy spheres about 120 nanometers across. Inside the sphere are three parts: the glucose detecting molecule, a color-changing dye, and another molecule that mimics glucose. When the particles are dissolved in water they look like food coloring, says Clark.

The three parts continuously move around the inside the hydrophobic orb. When they approach the surface, the glucose detecting molecule either grabs a molecule of glucose or the mimicking molecule.

If the molecules mostly latch onto glucose, the ink appears yellow. If glucose levels are low, the molecule latches onto the glucose mimic, turning the ink purple. A healthy level of glucose has a "funny orangey," color, according to Clark. The sampling process repeats itself every few milliseconds.

Time measured in milliseconds is much faster than then most current blood testing systems, and certainly less painful. But is it as accurate?

Glucose levels in the skin, where the ink would be injected subcutaneously, might not necessarily reflect the more critical measurement of glucose levels in the blood. Some studies show that skin glucose levels can lag up to 20 minutes behind blood glucose levels, while other show a much faster change.

"It's an interesting question," said Clark. "It's one that we might even be able to help answer."

Even if there is a significant lag time between blood and skin glucose levels, a small tattoo, in the several square millimeter range, according to Clark, would let diabetics know if an abnormally high or low reading was either returning to a normal level or getting worse.

Initial tests of the sodium-detecting ink in mice have had "spectacular" results, according to Clark. Testing the glucose monitoring nanotech ink in mice could begin by the end of this month.

Consumers will have to wait. Clark estimates that it will be at least two years before the necessary human testing is complete to bring the ink to the market.

Robert Rubin, a professor at Harvard Medical School, is excited by Clark's work at Draper.

"This will give me a great short cut for understanding what is happening inside the body," said Rubin.

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