Scientists have developed a glucose-monitoring system for diabetics that changes colour when glucose levels rise. University of Illinois engineers developed the glucose monitoring material from hydrogel, a soft elastic jelly-like material, laced with boronic acid compounds. Boronic acid binds to glucose, causing the gel to swell and expand as the glucose concentration rises. Embedded within the hydrogel is a photonic crystal made of tiny, carefully arranged beads.
A photonic crystal is like a mirror that only reflects one wavelength of light while the rest of the spectrum passes through. As the hydrogel expands, the reflected colour shifts from blue to green to red. Researchers have previously explored the possibility of using boronic acid hydrogels for glucose detection, because they are not prone to interference from most factors in the bloodstream. However, they have been met with a specific challenge inherent to the chemistry: Boronic acid likes glucose so much that, if there isn't enough glucose to go around, two boronic acids will bind to one glucose. This causes the hydrogel to shrink before the glucose concentration gets high enough for it to expand again. 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. The colour-changing material is simple and low-cost to manufacture, and a square inch of hydrogel could be enough for up to 25 patients. The researchers envision the hydrogel could enable continuous monitoring of patients hospitalised or in intensive care units, when patients are most critically in need of continuous monitoring - diabetic or not.