Polymers promote nerve cell growth - Regeneration - Brief Article

USA Today (Society for the Advancement of Education), June, 2003

Using microscale channels cut in ultrathin biodegradable polymers, Surya Mallapragada, a chemical engineering professor at Iowa State University, Ames, and an associate in materials chemistry at the U.S. Department of Energy's Ames Laboratory, is working to regrow nerve cells. The technique has been proven to work for peripheral nerve regeneration in laboratory rats.

When a nerve is severed, the part of the neuron "downstream" of the injury typically dies off. Neurons in humans are 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," Mallapragada explains. "Peripheral nervous system axons--the part of the nerve cell that carries the impulses--normally have a connective tissue sheath of myelin guide their growth, and without that guidance, they aren't able to grow productively."

By working on a cellular scale, she has found a way to help guide neurons so they grow in the right direction. Starting with biodegradable polymer films only a few hundred microns thick (100 microns equals 0.004 inches--significantly less than the thickness of a human hair), Mallapragada and her colleagues have developed methods for making minute patterns on these incredibly thin materials.

After very promising results during in vitro tests, the scientists collaborated on trials with rats, whereby tiny segments of their sciatic nerves were surgically removed and the severed nerves "spliced" using the polymer film. Although initially unable to use their legs, the rats started to regain use of them after three weeks and were able to function normally after six weeks.