An easy-to-swallow pill could replace daily insulin injections.
By radically changing the delivery of insulin, Robert Langer, a professor at the Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology (MIT), Cambridge, and his colleagues hope to make insulin treatment more palatable.
The research features in the journal Science.
Using microneedles to deliver the drug
The team came up with an innovative new design for a pill that consists of a biodegradable capsule containing an insulin microneedle. When a person swallows the pill, insulin injects directly into the stomach wall.
As the stomach lining does not have any pain receptors, the researchers believe that this way of delivering the drug will be free of pain.
"We are really hopeful that this new type of capsule could someday help diabetic patients and perhaps anyone who requires therapies that can now only be given by injection or infusion," explains Langer.
Microneedles are millimeter-size needles that scientists originally developed to penetrate the skin without causing pain.
The microneedle in this study had two components: a tip comprising compressed insulin, which penetrates the stomach wall, and a biodegradable shaft, which holds the tip in place.
Inside the capsule, the needle attaches to a compressed spring and a disc that the team created using sugar. The sugar disc dissolves when the capsule enters the stomach. By doing this, it releases the spring, allowing the microneedle to inject into the stomach wall.
This mechanism sounds deceptively simple, but what stops the microneedle from firing off in the wrong direction and missing the stomach wall?
"As soon as you take it, you want the system to self-right so that you can ensure contact with the tissue," says Giovanni Traverso, an assistant professor at Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
Taking inspiration from tortoise shells
The solution came from an unlikely place. Native to Eastern and Southern Africa, the leopard tortoise, which has a high domed shell, is an expert at self-righting.
Inspired by the tortoise shell's shape, the researchers used computer modeling to design the capsule. Irrespective of how the capsule lands in the stomach, its self-righting ability ensures that the needle makes contact with the stomach wall.
"What's important is that we have the needle in contact with the tissue when it is injected," explains Alex Abramson, a graduate student at MIT and first author of the study. "Also, if a person were to move around or the stomach were to growl, the device would not move from its preferred orientation."
After its injection into the stomach wall, the microneedle tip dissolves, and insulin enters the bloodstream. In the current study, this took roughly an hour, but the researchers can control the rate to some extent through the way in which they prepare the microneedle.
So far, the researchers have shown that they can deliver doses of up to 5 milligrams using this system.
The capsule itself passes through the digestive system without causing any side effects.
Further work on the capsule system is ongoing. The team is hopeful that this new design could spell the end for a host of drugs that it is currently only possible to deliver by injection.
"Our motivation is to make it easier for patients to take medication, particularly medications that require an injection. The classic one is insulin, but there are many others."