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Skin Patch Senses Glucose, Emits Insulin as Needed

Insulin patch

Insulin patch (Gu lab, UCLA)

4 Feb. 2020. A bio-engineering team developed a small patch worn on the skin that in lab mice and pigs senses blood glucose levels and releases insulin when required. Researchers from University of California in Los Angeles and other academic and industry labs describe the patch and their findings in yesterday’s issue of the journal Nature Biomedical Engineering (paid subscription required).

The team led by UCLA bio-engineering professor Zhen Gu is seeking a simple and reliable way for people with diabetes to monitor and control their blood glucose levels. Diabetes is a chronic disorder where the pancreas does not create enough insulin to process the sugar glucose to flow into the blood stream and cells for energy in the body. In type 2 diabetes, which accounts for at least 90 percent of all diabetes cases, the pancreas produces some but not enough insulin, or the body cannot process insulin. In type 1 diabetes, an autoimmune condition prevents islet or beta cells in the pancreas to produce insulin. According to the International Diabetes Federation, diabetes affects an estimated 463 million people worldwide, of which 31 million are in the U.S.

In earlier work, as reported in Science & Enterprise in March 2016, Gu’s lab then at North Carolina State University in Raleigh, created a polymer patch with beta cells that in lab mice produces insulin on demand. The patch, developed with endocrinologist John Buse at University of North Carolina in Chapel Hill, was designed as a simple, safe, and inexpensive alternative for people with diabetes who now need to measure their blood glucose levels and inject insulin, a process that is often painful and imprecise. In addition, current attempts at closed-loop or self-contained systems use invasive catheters, with mechanical sensors and pumps.

Gu’s lab — with colleagues at North Caroline State, University of North Carolina, MIT, and Zenomics Inc. — aim to improve on the earlier version. The patch tested in the study is made of a glucose-reacting polymer cured with a light-sensitive process. The patch contains micro-scale needles, less than one millimeter in length, enough to puncture outer layers of the skin, but without causing the pain of a pinprick needed to draw a drop of blood for conventional glucose testing or injecting insulin with a syringe. The micro needles are hollow and filled with insulin.

The needles, also made of glucose-sensitive polymer, puncture tiny blood vessels near the skin surface. When glucose levels in the blood exceed a safe level, phenylboronic acid in the polymer reacts to the glucose, causing the needles to swell, weakening the polymer’s matrix, and allowing release of the insulin.

The researchers tested the patch first with lab mice, then with mini-pigs. While pigs have organs that function similarly to humans, these pigs are smaller breeds, about 25 kilograms or 55 pounds each. In each case, the animals were induced with an insulin deficiency, and patches attached to their skin show they accurately sense excessively high glucose and release insulin as needed. The patch used with pigs is five centimeters or about two inches square, and functions for more than 20 hours.

“This smart patch,” says Gu in a UCLA statement, “takes away the need to constantly check one’s blood sugar and then inject insulin if and when it’s needed. It’s mimicking the regulatory function of the pancreas, but in a way that’s easy to use.”

Zenomics Inc. is a five year-old company co-founded by Gu to commercialize the insulin patch. Last year, the company joined FDA’s Emerging Technology Program that enables companies to discuss technical and regulatory issues with agency staff in advance of regulatory submissions. Gu is Zenomics’ board chair, while co-authors John Buse at University of North Carolina and Robert Langer of MIT are scientific advisers.

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