by Brendon Nafziger
, DOTmed News Associate Editor
With wars abroad leaving hundreds of young Americans missing limbs, a Congressional windfall could spur development of advanced prosthetics that connect nerve tissue to implants.
As part of a recently passed Department of Defense spending bill, the U.S. Congress gave the Center for Neuroprosthetics and BioMEMS (CNB), a division of the Bioengineering Institute at Worcester Polytechnic Institute in Worcester, Mass., $1.6 million to fund work on artificial limbs called neuroprosthetics.
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"The new funding is going to allow us to focus more carefully on several areas," W. Grant McGimpsey, Ph.D., a chemistry professor and the director of the Institute tells DOTMed News. "Essentially we want to learn how to induce normal functioning of neurons integrated with artificial material. The overriding picture of this is we want an implanted artificial limb."
One of the central challenges of creating a neuroprosthetic is the "neuro" part, getting nervous tissue to regrow or at least link up with the new limb.
Dr. McGimpsey's team's current strategy involves setting micro-wires as means of transporting action potentials, the electric firing of a neuron, from a nerve to sensors on the artificial appendage.
Eventually, Dr. McGimpsey hopes to use the micro-wires as scaffolding for new nerve growth. This is trickier, and involves converting stem cells into the appropriate kind of nerve cells. But Dr. McGimpsey intends to use his training as a surface chemist to create materials that encourage deposits of stem cells to become fully functional, differentiated new neurons.
"We can tailor the physical and chemical property of surfaces," he says. "We have to be able to tailor the surface, so it prompts these neurons to differentiate and function in the right way."
For many amputees, growing new nerve tissue is critical, as many of the nerves in the remnant limb are dead.
"If you damage a nerve, you have a few weeks before it dies," says Dr. McGimpsey.
But Dr. McGimpsey says now surgeons who amputate limbs work hard to save the nerves.
"If you look at typical amputations over the past thousands of years, there was no attempt to preserve viable tissue," he says. But now, "nerve bundles are being pulled back up into the residual limb and bunched there, and that allows them to continue living. [The surgeons] are prepping the person for the reconnection of the nervous tissue in the future."
But for those nerve bundles to be useful later, Dr. McGimpsey and his team have to tackle one of the unheralded challenges of devising a new limb: infections.