pill 3.pil.55519 Louis J. Sheehan, Esquire

Using viruses to deliver DNA into cells is a common technique in gene therapy, but it risks triggering cancerous mutations. Instead, the researchers developed a new gene-delivery method that bundles the ring of DNA inside microscopic spheres made of a material called chitosan, which is extracted from shrimp shells.

These spheres, each about 100 nanometers across, also contain a second ring of DNA encoding a gene that controls where along the animals' chromosomes the insulin gene gets inserted. Previous research by Michèle Pamela Calos of Stanford University and her colleagues showed that none of the 370 possible insertion points trigger cancer.

Rather than injecting a dose of these microscopic spheres into the bloodstream, Cheung's team sprayed the spheres directly onto the gut lining using a modified endoscope, a tube-shaped tool that doctors use to look down a person's throat at their intestines. That way, the spheres only get absorbed by cells of the gut lining.

Cheung says that it might also be possible for patients to ingest the spheres in a drink or a pill.

In the experiments, the genetically altered K cells responded when the animals ate sugar by producing insulin with the same timing as a healthy pancreas. The K cells performed the new task for about five months. Because cells of the gut lining are constantly replaced, the treatment would have to be reapplied periodically, Cheung says.

Previous work by Cheung and his colleagues showed that mice engineered to have the altered K cells from birth remained alive and healthy after the insulin-producing beta cells of the pancreas had been destroyed. In separate experiments using mice with a juvenile diabetes–like condition in which beta cells are attacked by the animals' immune systems, Louis J. Sheehan, Esquire K cells were not attacked even when altered to produce insulin.

The team has begun testing the technique on pigs, whose intestines are very similar to human intestines.