Color-Change Lenses Check Blood Sugar

ByPaul Eng

April 22, 2003 -- For diabetics, monitoring the amount of sugar in their blood is a crucial task that can be a literal pain in the finger.

And for years, doctors and researchers have been trying to develop less-intrusive glucose monitoring aids that don't require patients to stick themselves with needles to draw blood for testing.

But the latest research from scientists and doctors may lead to a device that helps diabetics keep watch on their glucose — just by looking into any mirror.

Sanford Ascher, a professor of chemistry at the University of Pittsburgh, has been studying "photonic crystals" — materials that signal the presence of certain chemicals by changing colors. And for the last three years, he and a team of researchers at the university have been experimenting with a photonic crystal that can detect glucose.

How It Works

The team's research is expected to be released in the May 1 edition of Analytical Chemistry, a publication of the American Chemical Society. But Ascher and other chemists say how the material works is fairly simple.

The photonic crystal is actually a gel made up of a proprietary combination of boronic acid and other chemicals. The chemicals form an array of long polymer chains, which contain receptors that bind to the structure of glucose.

The molecular spacing between the chains in the array changes as it comes into contact with glucose. The changes in spacing and volume of the array effectively alter how light passes through the material.

High concentrations of glucose produce spacing that causes light to refract, or bend, to produce a purple color. Low glucose would refract the light to produce a reddish color. Normal glucose levels would produce a green color.

Distinctive Diabetic Diagnostics

If the material can be used in a contact lens, it would detect the glucose carried in human tears, Ascher says.

"The ideal is that it's on the bottom edge of the lens and the diabetic patient would look in a mirror and see a color and relate it to a color wheel to [determine the] concentration of glucose," says Ascher.

Mark Arnold, a chemistry professor at the University of Iowa, says the approach taken by Ascher and his team is "very unique."

"Most glucoses [glucose monitors] use some type of enzyme," says Arnold, who is familiar with photonic crystals and Ascher's research work. "There is no other approach like this."

However, Arnold says he and other researchers are also working on other differing methods of non-invasive glucose detection as well. At an American Chemical Society symposium last year, for example, Arnold and his team presented a paper that proposed using beams of "near infrared light" that would measure glucose levels in cell fluids just under the skin. Another paper, from Gerard Coté at Texas A&M University, proposed a "smart tattoo" — special polymers that would be implanted under the skin and glow in the presence of glucose.

Wait and See

Arnold and the other researchers in non-invasive diabetes monitoring remain cautious about developments mainly because so much research still needs to be done.

"We still consider this work as research in basic mode," says Arnold.

David Finegold, a doctor of pediatric endocrinology at the University of Pittsburgh's School of Medicine and collaborator with Ascher, agrees that researchers have just begun to scratch the surface of the idea for a diabetes contact lens.

"The critical next observations are to better understand the dynamics of [glucose] in tears and blood glucose," says Finegold. "If we can figure out this relationship clearly, then we could use [the gel sensor] as effectively as the methods that draw plasma for glucose testing."

An in addition to ironing out scientific issues, creating the lens has been a matter of tedious handiwork for Ascher and his researchers. "Right now, we have to cut a piece of the gel out and glue it in to an existing contact lens," says Ascher. "We're hoping to find an easier way to do this."

Ascher notes that the team is taking steps to further the research this year. The university has already patented Ascher's work and is seeking investors to form a local startup company for further research and development work.

But Ascher is quick to admit that it will be several years before diabetics will be able to buy a glucose-monitoring contact lens.

"A commercial product has to get through federal Food and Drug Administration testing, and that's at least two or three years away," says Ascher.

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