A sweet change

By Bridget Hynes

Two researchers at the University have developed a sensor material out of hydrogel that monitors blood glucose levels continuously. In other words, the sensor can evaluate fluctuating levels of glucose­­ in the bloodstream in a linear fashion, instead of testing for it at different points in time. The developed sensor material is very thin — only 30 micrometers thick — and made of the same consistency as tofu. The researchers, Professor Paul Braun and materials science and engineering graduate student, Chunjie Zhang, said this inexpensive material has the potential to help two main groups of people: Intensive Care Unit patients who experience glucose fluctuation after surgery or traumatic injury and diabetics looking to monitor their blood sugar levels continuously.

For Mary O’Donnell, freshman in LAS who was diagnosed with diabetes at the age of 10, this sensor material could be beneficial if developed into an efficient monitoring device.

O’Donnell said that when she was first diagnosed, she was very good at remembering to test her blood sugar levels throughout the day, but once middle school came around, she tended to forget more. When she used a continuous glucose-monitoring device to try and solve this issue, however, she said she had problems with it. She then switched back to using the OneTouch glucose meter to prick her finger at different points throughout the day. Although this method is non-continuous, she said at the time it was a better option than the continuous monitor.

“The continuous monitor was a painful process having it in and then taking it out, and the monitor was also connecting through a radio device and sometimes it would go off and wake me up at night,” she said. “I had my monitoring device, and then I had a separate site on my body where the insulin pump was, but I couldn’t shower with either of them. I would have to take them off. They told me they didn’t want me to work with it, even if I had to take it off, because I worked at a swimming pool.”

O’Donnell said if she had any advice for future continuous glucose-monitoring systems, they should be less restricting and more accurate. She said if done the right way, these monitors have value.

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“Having your blood sugar continuously monitored is a really good benefit,” she said.

Braun and Zhang said that they are aware that continuous glucose monitoring systems already exist in the commercial market, but their sensor material is different.

“Existing products that are on the market now use enzyme electrodes to monitor glucose levels,” said Zhang. Using this method, glucose concentration is correlated with the intensity of electrochemical signals.

“Our approach uses a different chemistry to sense glucose,” said Zhang.

When the hydrogel material that they constructed comes in contact with glucose, it changes color, ranging on a scale of red to green, said Zhang. For each glucose concentration level, there is a corresponding color, and these colors are identified by their specific wavelength.

“Glucose concentration here is correlated with wavelength of light or color of light, which can provide accurate readings. Our approach is also cheap in cost. We offered an alternative design for continuous glucose monitoring, with a potential to meet many critical requirements for clinical use,” said Zhang.

The change in the gel’s color happens as the gel material, formally called polyacrylamide, expands. Small particles in the gel called polystyrene particles move apart when the gel expands. As the space between them changes, so does the way the gel manipulates light. This causes the change in the gel’s color.

Glucose in the blood stream is attracted to the gel, which contains boronic acid. When glucose floods into the gel from the bloodstream, the gel naturally expands. Braun and Zhang quickly discovered that, in order for their sensor to work, they needed to first add a volume-resetting agent called polyvinyl alcohol into the gel so that it would start sensing from its smallest form.

The resetting agent is important so that when the gel comes into contact with glucose it can only expand and not shrink. If the gel does not start at a shrunken state, it can react to contact with glucose by either shrinking or expanding, said Zhang. If this were to happen, one specific level of glucose concentration would be represented by two different colors on either end of the spectrum, and the results would not be accurate.

Braun and Zhang hope to eventually translate their sensor material into an actual sensor device.

“Our possible plan would be putting the sensor material in a glass fiber, and then we can thread the glass fiber into the blood stream through a needle,” said Zhang.

He said they are excited about the contributions a device like this could make in ICU units.

“The doctors in the ICU, they really want to know blood glucose fluctuations of patients. Usually after surgery, injury or any type of traumatic event, patients’

blood glucose concentration can fluctuate really badly because of the body trying to respond to the damage that the patient is experiencing,” said Zhang.

“With continuous glucose monitoring, the outcomes after surgery can be greatly improved,” he said.

Bridget can be reached at [email protected].