May 17, 2013
Injectable Nanogel Monitors Blood-Sugar Levels
redOrbit Staff & Wire Reports — Your Universe Online
Researchers at the Massachusetts Institute of Technology (MIT) have developed an injectable nanogel that can monitor blood-sugar levels and secrete insulin when needed, a breakthrough that could someday eliminate the need for patients with Type 1 diabetes to constantly monitor their blood-sugar levels and inject themselves with insulin.The researchers designed the nanoparticles to sense glucose levels in the body, and respond by secreting the appropriate amount of insulin, thereby replacing the function of pancreatic islet cells that are destroyed in people suffering from Type 1 diabetes.
A system like this could ensure that blood-sugar levels remain balanced, and improve patients´ quality of life, the researchers said.
Most people with Type 1 diabetes currently prick their fingers several times a day to draw blood for testing their blood-sugar levels. When levels are high, patients inject themselves with insulin, which breaks down the excess sugar.
“Insulin really works, but the problem is people don´t always get the right amount of it. With this system of extended release, the amount of drug secreted is proportional to the needs of the body,” said Daniel Anderson, an associate professor of chemical engineering at MIT and senior author of a paper describing the new system published May 2 in the journal ACS Nano.
Many researchers have sought in recent years to develop insulin-delivery systems that could act as an “artificial pancreas” by automatically detecting glucose levels and secreting insulin.
One method relied upon hydrogels to measure and react to glucose levels, but the gels were either slow to respond or lacked mechanical strength, allowing insulin to leak out.
The MIT team wanted to create a robust, biocompatible system that would respond more rapidly to changes in glucose levels, and would be easy to administer.
The new system consists of an injectable gel-like structure with a texture similar to toothpaste, said Zhen Gu, a former postdoc in Anderson´s lab.
Gu, now an assistant professor of biomedical engineering and molecular pharmaceutics at the University of North Carolina and North Carolina State University, said 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 created the gel to be sensitive to acidity, with each nanoparticle containing 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. This makes the local environment slightly more acidic, causing the dextran spheres to disintegrate, releasing insulin. The insulin then performs its usual function, converting the glucose in the bloodstream into glycogen, which is absorbed into the liver for storage.
The researchers conducted tests in mice with Type 1 diabetes, and found that a single injection of the nanogel maintained normal blood-sugar levels for an average of ten days. Because the particles are mostly composed of polysaccharides, they are biocompatible and ultimately degrade in the body.
The team is now working to modify the particles so they can respond to changes in glucose levels even 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 told MIT News.
Before testing the particles in humans, the researchers plan to further develop the system´s delivery properties and optimize the dosage.
The research team also included Robert Langer, the David H. Koch Institute Professor at MIT, and researchers from the Department of Anesthesiology at Boston Children´s Hospital.