WASHINGTON, Feb. 8 (Xinhua) -- American scientists developed a drug capsule that can deliver oral doses of insulin and it might replace the injections that people with type 2 diabetes have to make each day.

The study published in the Feb. 8 issue of journal Science reported the capsule, about the size of a blueberry and containing a needle made of compressed insulin.

In tests in animals, the researchers showed that they could deliver enough insulin to lower blood sugar to levels comparable to those produced by injections given through skin.

The needle comprised compressed, freeze-dried insulin on its tip and biodegradable needle shaft. The needle is attached to a compressed spring installed on a sugar disk, according to the study.

When the capsule is swallowed, water in the stomach dissolves the sugar disk, releasing the spring and injecting the needle into the stomach wall. The stomach wall has no pain receptors.

The researchers from Massachusetts Institute of Technology (MIT) were inspired by a tortoise called the leopard tortoise. The tortoise with a high, steep shell dome can right itself when rolling onto its back.

They created a similar shape for the capsule that can orient itself to ensure the needle is in contact with the lining of the stomach.

In this study, it takes about an hour for the insulin to be fully released into the bloodstream.

In tests in pigs, the researchers showed that they could successfully deliver up to 300 micrograms of insulin. Later, they managed to increase the dose to 5 milligrams, comparable to the amount that a patient with type 2 diabetes would need to inject.

"Our motivation is to make it easier for patients to take medication, particularly medications that require an injection," said the paper's co-author Giovanni Traverso, an assistant professor at Brigham and Women's Hospital and a visiting scientist at MIT.

"The classic one is insulin, but there are many others," said Traverso.