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.

"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."

NERVE GROWTH

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."

SKIN SEALANTS

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.

Although nerve growth may have the glamour, one of the main obstacles to creating artificial limbs implanted in the body is the risk of germs invading the implant site.

"If you think of your femur now, there's a lot of torque that takes place as you move around. There's movement of soft tissue that isn't perhaps completely in phase with movement of the femur," says Dr. McGimpsey. "If you twist skin around the wrist, the skin twists, the bone doesn't."

For an amputee, twisting the soft tissue could pull it away from the post, causing infection, further scarring or injury.

To combat that, Dr. McGimpsey and the other researchers are hoping to get bones to fuse with, say, titanium implants, and then somehow promote skin tissue to grow over the insertion site to act as a natural sealant, keeping out germs.

Infection-fighting is so critical, Dr. McGimpsey says, because these devices are expected to last at least half a century. And that's because they're being developed, in part, to help one of the 600 or so soldiers that The Given Limb Foundation, a charity, estimates are returning from Iraq as amputees.

"This is DoD funded work, and we're looking at helping the amputee soldier. These soldiers are in their twenties, they're healthy, they're going to be around for a long time. We need an implant strategy that guarantees there's no infection for 50, 60 years. That's a problem, especially with short residual limb amputation, as there's not a lot of bone to connect an implant to. If they get infected, you have to remove the implant, and you usually have to take bone with it. This is a one-shot strategy," Dr. McGimpsey says.

NOT THE FIRST TIME

While the grant money from Congress is helping research that could one day outfit young soldiers with new limbs, this isn't the first time the CNB, founded in 2006, got federal help. In 2007, Congress earmarked $1 million for the center. "That was through the support of Ted Kennedy, whose son is an amputee, so he had a very personal interest, as well as a national interest, in amputees," says Dr. McGimpsey.

The current grant's advocates were Senators John Kerry (D-Mass.) and Paul G. Kirk, Jr. (D-Mass.) and Rep. James P. McGovern (D-Mass.). The allocation is managed by the Army's Telemedicine and Advanced Technology Resource Center (TATRC).