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Special Contact Lenses Could Allow Diabetics to 'See' Glucose Levels

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JOHN MARGOLIS
For diabetics, monitoring blood sugar levels can be a pain in the finger--literally. The standard method currently requires several pinpricks a day to obtain small blood samples for testing. But new work could make these jabs unnecessary for the more than 10 million Americans diagnosed with the disease. According to a report to be published in the May issue of Analytical Chemistry, scientists have fashioned a material capable of monitoring glucose concentrations that could one day be incorporated into contact lenses.

A team of researchers from the University of Pittsburgh led by Sanford A. Asher and David Finegold has developed a thin plastic sensor that can detect changes in glucose levels in bodily fluids. The novel material consists of a crystalline array embedded in a watery gel. The researchers added specific groups to the gel that bind preferentially with glucose to form a complex of molecules. The presence of this complex causes more bonds to form within the gel, which changes its size and the way light passes through the material. According to the report, changes in glucose concentration induce color shifts across the visible range. A normal glucose level imparts a green color to the sensor, whereas dangerously low concentrations induce a red color and dangerously high levels cause it to turn violet.

Although the levels of glucose present in tear fluid are approximately 20-fold lower than those in blood, the researchers have shown in the laboratory that their material can detect the lower concentrations accurately. Human trials are at least a year away, but testing on rabbits is scheduled to begin soon, Asher says. Ideally, he notes, future diabetes patients will be able to wear contact lenses that have a small section of the plastic sensor embedded in them. A simple look in a mirror (and a comparison of the sensor's color to an accompanying color chart) could then alert them to potentially harmful blood sugar levels.

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