Researchers have developed a new drug delivery system for diabetics in which a sponge-like material surrounds the insulin core and releases insulin by expanding and contracting in response to blood sugar levels.
The technique could also be used for targeted drug delivery to cancer cells.
"We wanted to mimic the function of health beta-cells, which produce insulin and control its release in a healthy body," Dr. Zhen Gu, lead author of the paper describing the work and an assistant professor in the joint biomedical engineering program at North Carolina State University and the University of North Carolina at Chapel Hill, said.
"But what we've found also holds promise for smart drug delivery targeting cancer or other diseases," the researcher said.
The researchers created a spherical, sponge-like matrix out of chitosan, a material found in shrimp and crab shells.
Scattered throughout this matrix are smaller nanocapsules made of a porous polymer that contain glucose oxidase or catalase enzymes.
The sponge-like matrix surrounds a reservoir that contains insulin.
The entire matrix sphere is approximately 250 micrometers in diameter and can be injected into a patient.
When a diabetic patient's blood sugar rises, the glucose triggers a reaction that causes the nanocapsules' enzymes to release hydrogen ions.
Those ions bind to the molecular strands of the chitosan sponge, giving them a positive charge.
The positively charged chitosan strands then push away from each other, creating larger gaps in the sponge's pores that allow into the bloodstream.
As the insulin is released, the body's glucose levels begin to drop. This causes the chitosan to lose its positive charge, and the strands begin to come back together.
This shrinks the size of the pores in the sponge, trapping the remaining insulin.
The study is published online in ACS Nano.