Diabetes Forecast

On the Horizon: Insulin Delivery Patches

By Andrew Curry ,

Zhen Gu, PhD
Photo courtesy of NC State University

Zhen  Gu, PhD

Biomedical Engineer, University of North Carolina–Chapel Hill and North Carolina State University

Clinical Therapeutics/New Technology

ADA Research Funding
Pathway Accelerator Award

These days, Researchers are increasingly drawing on the natural world for inspiration, solving technological problems using forms and processes found in nature. Called biomimicry, the concept has yielded innovations such as Velcro, sharkskin swimsuits, and office buildings that cool themselves without costly air conditioning.

Now Zhen Gu, PhD, a biomedical engineer at the University of North Carolina–Chapel Hill and North Carolina State University, wants to use biomimicry to reduce the need for needles in daily diabetes care. He’s drawing on the human body’s natural processes to create a high-tech solution to insulin delivery: a “smart patch” with micro needles that’s applied to the skin. The patch would release insulin in tune with the body’s needs, in much the same way the pancreas does when it’s working properly.

The idea is to artificially recreate the way beta cells, the specialized factories that make insulin, work in a healthy pancreas. When the amount of glucose in the blood is high, insulin is produced and released.

After a meal, for example, the amount of glucose in the blood goes up. That prompts the beta cells to start pumping out insulin, which in turn tells muscle cells to absorb and store blood glucose to use as your body’s fuel. “Insulin is key to opening the door for blood sugar to go inside the cells,” Gu says.

The beta cells store insulin (in microscopic reservoirs called vesicles), ready to respond to rising blood glucose. When that happens, the vesicle walls open to release stored insulin into the bloodstream. When blood glucose drops, the vesicles close up, cutting off the flow of insulin until it’s needed again. “We want to mimic this behavior,” Gu says.

Gu is using chemistry to replicate that cellular mechanism. The first step is putting hundreds of microneedles on a quarter-sized flexible patch. The needles are 250 micrometers thick—about as wide as two strands of human hair—and between 600 and 800 micrometers long, or less than a quarter of the length of the smallest insulin pen needle on the market.

They’re long enough to tap into a network of tiny blood vessels, called micro-capillaries, just under the skin. “Injected insulin isn’t [shot] directly into the blood vessels,” Gu points out. It’s usually injected just under the skin and absorbed by these tiny blood vessels.

The needles are made of a specially formulated plastic. Like the body’s beta cells, they’re lined with insulin-filled vesicles that open and close in response to blood glucose levels. “We designed a glucose response together with a microneedle patch,” Gu says. “The microneedle senses the blood sugar level and releases insulin when the blood sugar level is high.”

Gu has tried the prototype patches on himself and says they hurt about as much as a mosquito bite. “It’s practically painless, especially when compared with traditional needles,” he says.

Most important, the vesicles in the microneedle patches would come packed with enough insulin to last for a while. “The concept is one patch, one day,” Gu says. “Every morning, you can put a patch on your arm or belly after a shower.” The dosage could be adjusted to account for a person’s typical daily insulin needs. The system would be responsive enough to maintain a constant blood glucose level, the equivalent of basal and bolus insulin in one package.

That could make a big difference, especially for young people with diabetes. “For children with type 1, needles are scary. Psychologically, a patch is easier,” Gu says. “We’re getting lots of e-mails from parents encouraging us.”

Gu has already tested the patches on mice genetically engineered to have diabetes. He’s now putting the patches on miniature pigs while continuously monitoring their blood glucose levels to make sure the patches release insulin the way they’re supposed to. He’s also talking with a large pharmaceutical company about ways to bring the patches to market in the next five years.

Zhen Gu, PhD Discusses His Research:

Help Support Diabetes Science

Zhen Gu, PhD, is one of 17 scientists who have been selected for funding from the ADA’s highly competitive Pathway to Stop Diabetes® initiative, which provides substantial, long-term financial and mentoring support to individuals exploring innovative approaches to diabetes research. If you would like to support diabetes research, please go to diabetes.org/researchdonation.

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