Nerve cells are unlike most other biological tissue. When a nerve is severed, the part of the neuron "downstream" of the injury typically dies off. And neurons in the human body can be several feet long. Grafting, which works well for other tissue such as skin, isn't the best option because of loss of nerve function where the donor tissue is removed and the difficulty in getting the nerve cells to line up and reconnect.
"Nerve cells aren't able to easily bridge gaps of more than one centimeter," says Surya Mallapragada, an Ames Laboratory associate in Materials Chemistry and a chemical engineering professor at Iowa State University. "Peripheral nervous system (PNS) axons the part of the nerve cell which carries the impulses normally have a connective tissue sheath of myelin guide their growth, and without that guidance, they aren't able grow productively."
Since the nervous system carries electrical impulses, it helps to think of nerve cells in terms of electrical wiring. Bundles of nerves are like an electrical cable with multiple wires. When a nerve "cable" is cut and cells die, it would be as though the copper wire downstream of the damage disappeared, leaving only the empty plastic insulation tubes. In order for new copper wiring to push out across the gap and fill in the empty insulation tubes, you'd need a way to guide the wires into the empty insulation. And that's where Mallapragada's research comes in.
By working on a cellular scale, she has developed a way to help guide neurons so they grow in the right direction. Starting with biodegradable polymer films only a few hundred microns thick (
Contact: Surya Mallapragada