Insulin Delivery From New Injectable Smart Sponge
July 18, 2013

New Smart Sponge Holds Promise For Diabetes And Cancer Treatment

Rebekah Eliason for - Your Universe Online

A sponge like material surrounding insulin is one of the newest drug delivery methods developed for diabetes. The pores in the sponge expand and contract as the body needs insulin. There is hope that this technique could also be used to deliver targeted cancer cell treatment.

Dr. Zhen Gu, professor of biomedical engineering, explained "We wanted to mimic the function of health beta-cells, which produce insulin and control its release in a healthy body. But what we've found also holds promise for smart drug delivery targeting cancer or other diseases."

Researchers developed the sponge material from chitosan, which is formed using chitin found in the exoskeletons of shrimp and crabs. The spherical sponge surface contains many tiny pores along with nanocapsules made from a porous polymer. Inside the tiny capsules is a substance called glucose oxidase. This matrix surrounds a reservoir containing insulin.

As a diabetic person's blood sugar level raises, glucose reacts with the nanocapsules causing them to release hydrogen ions. These ions bind to chitosan strands creating positive charges all over the sponge that push away from each other, which causes the openings in the sponge to get larger and release insulin into the bloodstream. Insulin, the hormone that transports glucose in the bloodstream, is needed in both type 1 and type 2 diabetes patients to regulate blood sugar levels.

Once insulin is released into the bloodstream, glucose levels drop making the chitosan strands lose their positive charge and shrink back to normal size. This traps the remaining insulin inside the sponge.

For cancer cell treatment this sponge technique could be simplified even further. Cancerous tumors are naturally acidic environments full of hydrogen ions. The enzyme used in the sponge material to treat diabetes could be eliminated, and the pores would be triggered to open when exposed to the hydrogen ions in the environment of cancer cells. Instead of insulin, the material would be filled with anticancer drugs.

Gu said "We can also adjust the size of the overall 'sponge' matrix as needed, as small as 100 nanometers, and the chitosan itself can be absorbed by the body, so there are no long term health effects."

During lab tests involving mice, researchers found the sponge technique to be effective at reducing blood sugar in the bloodstream for 48 hours. In May, a report on a separate "smart system" was published that effectively maintained blood sugar levels for ten days.

"We learned a lot from the promising 'sponge' research and will further optimize it. Meanwhile, we are already exploring applications to combat cancer," Gu said.

"Glucose-Responsive Microgels Integrated with Enzyme Nanocapsules for Closed-Loop Insulin Delivery" was published in the online journal ACS Nano. Research was supported by a grant from the Leona M. and Harry B. Helmsley Charitable Trust Foundation, and a gift from the Tayebati Family Foundation.