Chameleon-like gel could track blood sugar levels in real time

A sample of the hydrogel turns from blue to green to red, as it takes up glucose
A sample of the hydrogel turns from blue to green to red, as it takes up glucose
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A sample of the hydrogel turns from blue to green to red, as it takes up glucose
A sample of the hydrogel turns from blue to green to red, as it takes up glucose

Thanks to a new color-changing hydrogel, there may soon be a more reliable way of continuously monitoring the blood glucose levels of both diabetics and hospital patients. If incorporated into a device such as an implanted pump, it could automatically trigger the release of insulin into the bloodstream as needed.

Created by Prof. Paul Braun and graduate student Chunjie Zhang at the University of Illinois, the hydrogel is laced with boronic acid compounds, plus it also contains photonic crystal beads.

Because the acid naturally binds to glucose, the gel draws in glucose that’s present in its environment, swelling in size as it does so. As the gel expands, the arrangement of the crystal beads is altered, changing the manner in which they reflect light. As a result, the gel shifts from its default blue color to green, and then to red. By analyzing the exact hue of the gel, the concentration of glucose can be determined.

The use of such boronic acid gels has been explored before, but there’s been one problem – when concentrations of glucose are too low, two acid molecules will bind with a single glucose molecule, actually causing the gel to shrink. By adding a chemical known as a volume resetting agent, however, the U Illinois scientists have been able to essentially "preshrink" the hydrogel, so that even a little glucose will still cause it to expand.

The gel should reportedly be inexpensive to produce, with about one square inch providing enough material to monitor up to 25 patients. Other continuous glucose monitoring technologies do already exist, although Braun believes that they have severe limitations.

"The systems available today all have some combination of limited sensitivity, limited precision and frequent recalibration," he said. "Using today’s systems, you can determine trends in glucose levels, but without frequent recalibration, you don’t have the accuracy or reliability to use that to make insulin dosing decisions or to drive autonomous dosing."

A system utilizing his hydrogel shouldn’t require such frequent recalibration, plus it ought to be highly accurate. Along with its possible use in implanted insulin pumps, Braun also envisions it being utilized in sensors mounted on the end of fiber optic cables, that are inserted into hospital patients’ veins along with their IVs to allow for continuous monitoring.

A paper on the research was recently published in the journal Advanced Materials. The gel can be seen changing color in the video below.

Source: University of Illinois

Color-change glucose meter

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