The MIT team set out to create a sturdy, biocompatible system that would respond more quickly to changes in glucose levels and would be easy to administer.
Their system consists of an injectable gel-like structure with a texture similar to toothpaste, says Gu, who is now an assistant professor of biomedical engineering and molecular pharmaceutics at the University of North Carolina at Chapel Hill and North Carolina State University. The gel contains a mixture of oppositely charged nanoparticles that attract each other, keeping the gel intact and preventing the particles from drifting away once inside the body.
Using a modified polysaccharide known as dextran, the researchers designed the gel to be sensitive to acidity. Each nanoparticle contains spheres of dextran loaded with an enzyme that converts glucose into gluconic acid. Glucose can diffuse freely through the gel, so when sugar levels are high, the enzyme produces large quantities of gluconic acid, making the local environment slightly more acidic.
That acidic environment causes the dextran spheres to disintegrate, releasing insulin. Insulin then performs its normal function, converting the glucose in the bloodstream into glycogen, which is absorbed into the liver for storage.
In tests with mice that have Type 1 diabetes, the researchers found that a single injection of the gel maintained normal blood-sugar levels for an average of 10 days. Because the particles are mostly composed of polysaccharides, they are biocompatible and eventually degrade in the body.
The researchers are now trying to modify the particles so they can respond to changes in glucose levels faster, at the speed of pancreas islet cells. "Islet cells are very smart. They can release insulin very quickly once they sense high sugar levels," Gu says.
Before testing the particles in humans, the researchers pl
|Contact: Sarah McDonnell|
Massachusetts Institute of Technology