Networking with friends: nanotech material reconnects severed neurons.

A new material made of nanometer-size protein particles appears to be capable of bridging the gap between severed nerves. The finding could lead to an effective early treatment for spinal cord injuries, traumatic brain injuries, or strokes--conditions that affect millions of people worldwide.

When these injuries damage the long arms, or axons, that join neurons, the surrounding cells form scar tissue in the fissure. This blocks neural connections. Few therapies have been successful in reinstating these lost connections in people, says Rutledge G. Ellis-Behnke, a neuroscientist at the Massachusetts Institute of Technology (MIT).

"What our research looks at is how to restore quality of life to these people" he says. "It may be as simple as being able to reconnect these disconnects in the brain."

Seeking such reconnections, the scientists designed a synthetic chemical to act as a temporary scaffold to support neurons as they grow extensions across the gaps in severed axons. This material, which the team named the self-assembling peptide nanofiber scaffold (SAPNS), is made up of particles of protein. The material forms a mesh when mixed with the fluid that permeates the brain.

Ellis-Behnke's team tested SAPNS on damaged nerves in hamsters. The researchers first severed one of each animal's optic nerves, rendering all the hamsters blind in one eye. Immediately following this operation, some of the animals received an injection of the scaffold material where the nerve was severed. Other animals received an injection of saline.

Three months after the surgery, the scientists tested the animals' vision. Although no hamster that received saline showed any sign of vision in its eye on the side with the damaged optic nerve, about 75 percent of animals that received SAPNS regained some vision, as indicated by turning their heads when offered a treat on their formerly blind side.

When scientists peered into the animals' brains, they found that the saline-injected hamsters had extensive scar tissue where the nerve was severed. However, in those animals that had received SAPNS, there was no visible scar tissue. "It actually looks like the tissue knit itself together into one continuous piece," says Ellis-Behnke. His team reports the results in an upcoming Proceedings of the National Academy of Sciences.

Ellis-Behnke notes that he and his collaborators still need to answer several questions about how SAPNS works. For example, it's unclear whether the material would have a similar effect if administered hours or days after nerve damage occurs, a more realistic scenario for most injuries in people.

Once scientists iron out these wrinkles, SAPNS or a related chemical could offer new ways to repair brain damage, says Edward J. Tehovnik, an MIT neuroscientist who didn't participate in the study. "The work has the potential of opening up a new field of study in the area of nanotechnology and brain repair," he says.