"It's like people each using two arms to pull together two ropes of the polymer network, so the hydrogel shrinks," said Chunjie Zhang, a graduate student and first author of the paper. "When more glucose comes in, each boronic acid can have its own glucose. Now, each person only grabs one rope, so the hydrogel expands."
The Illinois researchers devised a solution to this problem by introducing a third chemical, called a "volume resetting agent," to bind up the boronic acid before the glucose is added, pre-shrinking the gel and giving a baseline for measurements. This development enabled the Illinois researchers to capitalize on the advantages of a boronic acid system without the limitation of shrinking at lower concentrations.
"When we introduce the volume resetting agent, it grabs all the ropes and makes the hydrogel shrink," said Zhang. "Then when glucose comes in, it releases the volume resetting agent from the ropes and expands the hydrogel."
The color-changing material is simple and low-cost to manufacture, and according to Braun, a square inch of hydrogel could be enough for up to 25 patients.
The researchers envision the hydrogel as part of a subcutaneous system or a sophisticated device that taps into the bloodstream an insulin pump, for example. However, the application they are most excited about is in short-term continuous monitoring of patients hospitalized or in intensive care units, when patients are most critically in need of continuous monitoring diabetic or not.
"The sensor would be put on the end of a fiber optic cable, for example, and threaded into the bloodstream along with IVs or other monitors," said Braun. "You could just slide it into an open port. Then you can monitor the patient for several days or
|Contact: Liz Ahlberg|
University of Illinois at Urbana-Champaign