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A way to spot glucose

In the quest for less invasive ways for diabetics to measure blood sugar levels, scientists are working on a specially designed contact lens.

September 08, 2003|Shari Roan | Times Staff Writer

To test their glucose levels, diabetics need to prick their finger and draw blood, usually several times a day. Eventually, they may have a better way.

Teams of researchers around the country are working on noninvasive ways to monitor blood sugar. One of the most intriguing approaches would use a glucose sensor built into a contact lens.

Scientists at the University of Pittsburgh recently announced that they've created a sensor material that changes colors when it reacts with glucose levels in body fluids. Their plan is to embed the material into a contact lens; patients would look in a special mirror that contains a glucose measuring chart, matching the color on the lens to the corresponding glucose level.

Although much work remains to be done on the device, the scientists are confident that they will eventually produce a noninvasive glucose test for the nation's 11 million diabetics.

"Unfortunately, the present ways to monitor glucose involve a finger or arm stick," says Sanford A. Asher, a Pittsburgh chemistry professor who has led the research along with Dr. David Finegold, a professor of pediatrics. "Because of the pain, people don't do it enough. And for children, it's just awful. If there were a noninvasive way of doing it, that would really change the whole thing."

The material devised by Asher and Finegold is based on 20 years of research on photonic crystals, which control the direction of light movement. A device containing photonic crystals can respond to the amount of a particular chemical by changing color.

"We asked ourselves: What is the most important chemical to sense? The obvious answer is glucose," Asher says. The researchers hope to eventually develop materials that could sense other chemicals, such as chemical warfare agents or various constituents of blood.

Asher and his colleagues published a paper on its sensor material in May in the journal Analytical Chemistry. Now they have turned the project over to a company that intends to develop the contact lens glucose sensor.

The sensor material, which would likely be embedded in only part of the lens, will be designed to measure glucose in tear fluid. According to Asher, the concentration of glucose in the tear fluid reflects that in the blood.

The research has been challenging because other substances in tear fluid, such as proteins and salt, can interact with the glucose. Although that obstacle has been overcome, researchers still worry about the reliability of the system if people tear up easily. "Crying would be a problem," Asher says.

Animal and human testing is set to begin soon, and Asher predicts a product could be available in four years. "We know we can do it. We've gone past the basic science," he says. "Now we're working on the engineering."

Advocates for diabetes patients say the advent of noninvasive glucose monitoring would dramatically alter the lives of many patients.

"For years, there has been this elusive goal to find a noninvasive way to test glucose," says Dr. Nathaniel Clark, national vice president for clinical affairs at the American Diabetes Assn. Advances in treating the disease have led to more frequent blood sugar monitoring, up to 12 times a day for some people. "If you ask people: What is the worst part of having diabetes? They all say, 'Having to test your blood sugar,' " Clark says.

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More ideas for monitoring glucose

Other scientists are working on additional ways to measure blood sugar without having to breach the skin. These approaches include:

* A watch-like device worn on the wrist that uses small amounts of electricity to draw glucose through the skin for testing.

* Infrared light that focuses on the skin and records the concentration of glucose.

* Interstitial fluid devices, which monitor fluid in the small spaces between tissues or organs, that are pressed to the skin to obtain a glucose reading.

* Implantable glucose sensors that provide continuous readouts on devices worn outside the body.

Source: Times research

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