Bloodless test for glucose runs skin-deep.

Many people with diabetes have to puncture their skin with a needle several times a day to check the glucose concentration of their blood. That's an uncomfortable, inconvenient procedure.

Now, researchers at the State University of New York at Buffalo have found that it may be possible to monitor glucose without drawing blood. They simply collect and measure the glucose that diffuses naturally through the skin.

"In the past, people have not explored these [methods] because we did not have the technology to detect the small quantities that go through the skin," says chemist Luis A. Colon. He and his colleagues are currently developing an extremely sensitive measure.

The scientists collected glucose samples from volunteers by attaching a small cup of water to the skin for 5 minutes. Next, they added an enzyme that changes glucose into hydrogen peroxide. Then, they allowed the hydrogen peroxide to react with homovanillic acid to form a fluorescent compound. The intensity of the fluorescence indicates the glucose concentration in the solution.

The amounts of glucose in the water samples don't correlate directly with those detected in the volunteers' blood, but the samples do seem to reflect changes in glucose concentration, says Colon. After the volunteers swallowed glucose tablets, the concentration increased in both their blood and skin.

The scientists also collected samples by using a method that places an electric voltage across the skin to enhance the flow of fluids (SN: 11/20/93, p. 327). However, this causes irritation, so the team has focused on the passive collection method.

Eventually, Colon and his group would like to develop a small sensor that could be attached to the skin to provide a continuous glucose readout. They are also testing other bodily fluids, such as tears and saliva, that can be collected painlessly and might contain valuable biochemical information.