A “smart insulin patch” created by researchers at the University of North Carolina and North Carolina State University detects increases in blood sugar levels and secretes doses of insulin into the bloodstream whenever needed.

The patch – a penny-sized thin square – is covered with more than one hundred tiny needles, each about the size of an eyelash. The “microneedles” are packed with microscopic insulin-storage units and glucose-sensing enzymes that rapidly release the insulin when blood sugar levels become too high.

Researchers have tried to remove the potential for human error by creating “closed-loop systems” that directly connect the devices that track blood sugar and administer insulin. Such approaches, however, involve mechanical sensors and pumps, with needle-tipped catheters that must be stuck under the skin and replaced every few days.

The new smart patch attempts to emulate the body's natural insulin generators. Using hyaluronic acid (HA), a natural substance found in many cosmetics, and the organic compound 2-nitroimidazole (NI), the researchers created artificial vesicles to store the insulin and enzymes specially designed to sense glucose.

Zhen Gu, PhD, a professor in the Joint UNC/NC State Department of Biomedical Engineering, and his team tested the patch in a mouse model of type 1 diabetes. One set of mice was given a standard injection of insulin; their blood glucose levels dropped to normal levels and they then quickly climbed back into the hyperglycemic range.

When the researchers treated another set of mice with the microneedle patch, blood glucose levels were brought under control within thirty minutes and remained steady for several hours.

In addition, by varying the dose of enzyme contained within each of the microneedles, the team found that they could tune the patch to alter blood glucose levels within specific ranges.

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