What's the News: Engineers and patients dream of mechanical prosthetic limbs that can talk and listen to the brain, moving in response to thought and sending back sensory information. For that dream to become reality, electrodes from the prosthetic have to connect with nearby nerve cells---a tricky proposition, given that nerve cells in an amputated limb won't grow without proper structural support. A new tubular scaffold, described in detail by Technology Review, has tiny grooves that fit bundles of nerve cells, which could provide the support nerves need to interface with a mechanical limb better than current designs. How the Heck:
The scaffold is made of a grooved polymer sheet (think pleated fabric or corrugated cardboard) rolled into a spiral. The resulting channels in the scaffold are just the right size and shape for bundles of nerve cells to grow through.
Those channels do double duty, not just supporting the nerve cells but picking up their electric signals---which could then be sent on to electrodes in a mechanical limb.
So far, the researchers have grown Schwann cells, glial cells that support peripheral nerve cells, and dorsal root ganglion cells, which carry information about touch and proprioception from the limbs to the spinal cord, on the scaffold. Both types of cells grew robustly, aligned themselves with the channels in the scaffold, and sent projections towards the channels.
Eventually, this scaffold could support both main types of peripheral nerve cells---those that send orders from the brain to the limbs, and those that relay sensory information from the limbs back to the central nervous system---providing a pathway for both feeling and motor function components to connect with the prosthetic.
What's the Context:
Current nerve cell scaffolds have significant shortcomings: nerves don't grow particularly well on them, or they only have a few channels for nerves to grow in, limiting the dexterity of the prosthetic limb.
Researchers are also investigating ways the central nervous system can control prosthetics. For instance, one team devised a technique that let monkeys control robotic arms with their thoughts via electrodes implanted in their brain.
DARPA also has a project to design prosthetics that connect to both sensory and motor nerves in the amputated limb.
Not So Fast:
The current prototype doesn't have electrodes; the researchers plan to add gold electrodes and test the scaffold in rats.
The scaffold is an early proof-of-concept model, nowhere near ready for use in people.
Reference: A. Srinivasan, L. Guo, and R. V. Bellamkonda, "A Novel Microchannel-Scaffold Electrode Array for Peripheral Nerve Interfacing," Society for Biomaterials 2011 Annual Meeting & Exposition, Orlando, Florida, April 13-16, 2011. Image: Wikimedia Commons / BotMultichillT