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Smart Insulin Patch Designed to Regulate Blood Glucose

Smart insulin skin patch

Smart insulin skin patch (Zhen Gu Lab, Univ. of North Carolina, Chapel Hill)

23 June 2015. A skin patch made with tiny needles can dispense insulin and regulate blood glucose levels in lab mice for up to 9 hours. The device is being developed by a joint biomedical engineering department at University of North Carolina in Chapel Hill and North Carolina State University in Raleigh, and described in yesterday’s issue of Proceedings of National Academy of Sciences (paid subcription required).

The patch is under development in the labs of biomedical engineering professor Zhen Gu in Raleigh and endocrinologist John Buse in Chapel Hill. Gu, Buse, and colleagues aim to help people with diabetes better control their blood glucose levels with a simple, safe, and inexpensive device. People with diabetes, numbering in the hundreds of millions worldwide and growing, 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.

With the patch, the researchers are seeking to emulate the body’s natural system of making, storing, and delivering insulin, where beta cells in the pancreas make insulin, and store it in tiny sacs known as vesicles. When more glucose enters the blood stream, normally functioning beta cells sense the higher levels and respond by making and delivering more insulin.

The team designed the device to also store and dispense insulin with vesicles that form from a reaction of two biocompatible chemicals: hyaluronic acid and 2-nitroimidazole. Hyaluronic acid occurs naturally in the eyes and joints, while 2-nitroimidazole is a natural antibiotic. Combining the two chemicals creates a substance that both seeks and repels water, creating a tiny, nanoscale open space resembling a vesicle. The researchers then fill that space with insulin in solid form and enzymes that react in the presence of glucose.

The patch consists of about 100 of these vesicles in microneedles — which the researchers say pierce the very outer layers of skin, but are too small to cause pain — arrayed on a square sheet about the diameter of a penny. When the enzymes in the vesicles are in the presence of glucose, they oxidize the glucose producing gluconic acid, which consumes oxygen and upsets the equilibrium of the vesicles, causing the vesicles to break open and release insulin into the bloodstream.

The team tested the patch with lab mice induced with type-1 diabetes, the autoimmune disorder affecting about 5 percent of population with diabetes. The mice receiving the patch were able to restore safe blood glucose levels within 30 minutes and lasting up to 9 hours. Mice receiving insulin injections also brought glucose levels under control quickly, but glucose levels also rebounded quickly into dangerously high levels. In addition, the researchers found they could adjust enzyme levels in the patch to keep blood glucose levels within a predetermined range, reducing the risk of receiving too much insulin and driving glucose levels down too far.

The patch still needs more preclinical testing even before clinical trials with humans, but the researchers believe they can design a device that people with diabetes need to change every few days, and customized for each individual’s condition. “The whole system can be personalized to account for a diabetic’s weight and sensitivity to insulin,” says Gu in a university statement, “so we could make the smart patch even smarter.”

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