Painful problem: Most sufferers of type 1 diabetes have to inject themselves within insulin several times a day.

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SYDNEY: A new oral drug delivery system for insulin may herald the end of daily injections for some diabetics, researchers report.

Diabetics are unable to control the level of sugar in their bloodstream. The disease results from an inability to produce or properly use the hormone insulin, which is vital for metabolising sugar. Symptoms can include excessive urination and thirst, blurred vision, unexplained weight loss and tiredness.

Safe passage

Patients suffering from the more severe 'type 1' diabetes typically inject insulin several times a day in order to stabilise their blood sugar levels. But now, a study reports a capsule that could be taken orally, which would decrease the need for injections to once every five or six days.

According to researchers behind the study, at the University of Texas in Austin, U.S., insulin currently has to be injected to get it directly into the bloodstream. The hormone is unable to survive the gastric acid and protease enzymes of the human intestinal tract and is also difficult to absorb.

The trick, then, said lead researcher and chemical engineer, Nicholas Peppas, was to find a material that could protect the insulin as it goes through the digestive tract, and would release it at a point where it would make it to the blood stream.

Peppas and his team tested several types of non-toxic plastics, called biopolymers, in the hope of finding one that could stand up to gastric and intestinal fluids. This gel-like biopolymer was then used to encapsulate the insulin. The technology is detailed in the American Chemical Society journal Biomacromolecules.

In subsequent testing of the capsules, the researchers were able to show that the hormone passed undigested through the acidity of the stomach. When the biopolymer capsules reach the small intestine they are able to temporarily attach to the intestinal wall, improving absorption. Here the change from an acidic to a neutral environment causes the porosity of the material to increase, releasing the insulin, where it can cross into the bloodstream.

Larger doses

The system is not foolproof, because only 30 per cent of the insulin made it into the bloodstream during the tests. However, this can be corrected for by administering a larger dose, said Peppas.

The study is the first to use a material that gets over the problem of high pH in the stomach and subsequent problems with absorption in the intestine. "The finding is significant because this is the first time patients previously obliged to do injections have a possible different way of taking insulin," said Peppas.

"At present there are numerous studies that are trying to find ways of overcoming these problems including encasing the insulin in various ways," commented Trevor Tye with the NSW branch of Diabetes Australia in Sydney. "The current published work is novel in that attempts to address both the problems [at once]."

Though the work is promising, it "needs more study … before we can say that this could be another reliable and safe insulin delivery method," added endocrinologist Stephen Twigg of the Royal Prince Alfred Hospital, also in Sydney.

Peppas said that clinical trials will begin next year, and his team are already in talks with industry representatives.