Pushing the frontiers of drug delivery technology, a biomedical engineer at the University of Illinois at Chicago has developed an implantable capsule that releases a steady supply of insulin to the bloodstream of people with diabetes.

The biocapsule contains insulin-secreting cells. A silicon membrane containing nano-scale pores allows the insulin out and keeps out antibodies secreted by the immune system. Image credit: Kirk Woellert/NSF a larger version is here

The biocapsule, developed by Tejal Desai with support from the National Science Foundation (NSF), features two innovations designed to overcome previous obstacles. A biological process allows the capsule to continuously produce insulin, rather than using up a limited supply. The capsule is made of a material designed to overcome the problem of implant rejection.

"The capsule essentially acts as a bioreactor; it contains insulin-secreting cells that borrow nutrients from the body to keep producing insulin indefinitely," Desai said. "As long as the body produces glucose, the cells will respond with insulin."

Desai has also broken new ground by developing a successfully implantable micro-scale device. Tiny devices made with microchip technology have been researched extensively for implantable medical applications, but biocompatibility has been a continuing problem.

To prevent the capsule from being attacked and destroyed by the immune system, Desai developed a silicon membrane covered with tiny uniform pores, each seven nanometers across. The membrane acts as a "microfilter," allowing the secretion of insulin from the capsule but blocking the entrance of antibodies. The membrane is fabricated with photolithographic techniques commonly used for silicon microchips.

Desai reported the results of short-term testing of the capsule, and the prospects for other micro-devices for drug delivery, today at a meeting of the American Vacuum Society in San Francisco, California. The results will be published in the November issue of IEEE Transactions in Biomedical Engineering.

The next steps are testing the capsule for long-term usage and evaluating the ideal dosage level.