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Capsule Designed to Inject Insulin in Stomach Wall

Tanzanian leopard tortoise

Tanzanian leopard tortoise (photoboel, Pixabay)

8 Feb. 2019. A biomedical engineering team created a capsule that in animal tests releases a tiny needle delivering an insulin dose to the stomach lining, equivalent to conventional insulin injections. Researchers from Massachusetts Institute of Technology in Cambridge and drug maker Novo Nordisk in Copenhagen, Denmark describe the device and tests in today’s issue of the journal Science (paid subscription required).

People with diabetes need to regularly take insulin, usually as self-delivered injections under the skin. 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. According to the International Diabetes Federation, diabetes affects an estimated 425 million people worldwide, of which 46 million are in North America.

As an alternative to injections, researchers at MIT designed a capsule, small enough to be swallowed, but containing an insulin delivery system that works in the stomach. The team led by biomedical engineering and materials science professor Robert Langer and gastroenterologist Giovanni Traverso — now at Brigham and Women’s Hospital in Boston, but soon to join the MIT faculty — had to meet a number of challenges to create this device, starting with insulin’s large-molecule chemistry. Insulin on its own interacts with gastric juices in the stomach preventing it from reaching the blood stream in sufficient quantities to be effective, thus the need for direct injections of insulin.

The physical actions of the stomach also offer challenges for delivery of insulin, particularly thick mucous layers and muscular contractions making the stomach an unpredictable environment for reliable drug delivery. The authors note that earlier devices seeking to navigate this environment succeeded in delivering drugs with only about 1 percent bioavailability. But the thicker stomach wall, 4 to 6 millimeters, also offers more space and better protection than the intestine for drug delivery.

To deliver insulin reliably in the stomach, Langer, Traverso, and colleagues devised a device they call a self-orienting millimeter-scale applicator, or Soma. For the device’s physical shape, the team was inspired by the leopard tortoise found in Africa with a peaked shell over a flat and heavier lower body. With this shape and low center of gravity, the tortoise can easily right itself when upended. With this same principle, Soma devices land with the flat bottom on the stomach wall, despite being tossed and turned by stomach activity.

The next challenge was to deliver the insulin into the stomach wall. For this task, the researchers designed a tiny needle, 7 millimeters long, made of biodegradable polymers. The needle can hold up to 0.5 milligrams of concentrated insulin inside a cone-shaped, spring-activated delivery mechanism. That device is contained inside a coating of sugar that melts in the humid stomach environment in about 4 minutes. The mechanism is smaller than some medical devices approved by FDA to work in the stomach, allowing it to safely pass through the digestive tract. And the entire ingestible capsule is about the size of a blueberry.

The team first tested the Soma device in lab mice for toxicity, then gave the capsules to pigs, which have digestive systems and organs similar in size to humans, in this case in a fasted state. The device needles contained 0.3 milligrams of human insulin, which they safely delivered and released into the blood stream in about an hour. The pigs suffered hypoglycemia, or low blood glucose levels from the excess insulin in the experiments, but were rescued with dextrose. Endoscope examinations show the devices passed through the pigs without damaging their digestive tracts.

While the study was designed to prove the concept, researchers believe the results show a Soma device can be adapted for other biologic drugs, including proteins and nucleic acids. Novo Nordisk, a developer of diabetes drugs which helped fund the project, tells the New York Times it expects to begin clinical trials of Soma in about 3 years.

And as reported by Science & Enterprise just last month, Traverso is co-founder and a board member of Lyndra Therapeutics Inc. in Watertown, Massachusetts developing long-term drug delivery technologies for Alzheimer’s disease and psychiatric disorders. The following video tells more about the Soma device.

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