Tiny spheres may deliver oral insulin

The lives of diabetes patients could become easier if a new insulin-containing material makes its way into pills. Many people with diabetes take several insulin shots each day to control their blood sugar. They’d prefer to take the hormone orally, but it’s difficult to protect doses as they pass through the acidic stomach and yet keep the insulin available for the small intestine to absorb.

Now, chemists at Purdue University in West Lafayette, Ind., have developed a new way to sneak insulin past the stomach and make it better able to cross the intestine’s lining. Aaron C. Foss and Nicholas A. Peppas put the hormone inside microscopic balls of acid-sensitive polymers.

The nanoscale spheres contract in acidic environments and swell in nonacidic ones. By soaking the balls in a nonacidic solution containing insulin, Foss made them expand and absorb the drug. Then, he quickly increased the solution’s acidity, and the balls contracted, holding the insulin tight inside.

The researchers have tested their insulin-loaded spheres in beakers of solution simulating the gastrointestinal tract. The results indicate that the spheres stay compact while traversing the stomach and thus protect the insulin, says Foss. In the less-acidic small intestine, the balls should swell and release the drug. Adding to the spheres’ appeal, they are expected to grab onto the intestinal lining and pull out calcium ions, which normally hinder insulin’s passage to the blood.

The team also put the balls into gelatin tablets for tests on rats and dogs. Sixteen percent of the administered insulin reached the bloodstream. Other studies have reported that 0.1 percent of unprotected oral insulin turns up in blood.

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