[tt] Nanotubes improve neuro-stimulators

[Hughes, James J.]

http://www.eurekalert.org/pub_releases/2008-09/usmc-cie091508.php

Coating improves electrical stimulation therapy used for Parkinson's,
depression, chronic pain

DALLAS - Sept. 16, 2008 - Researchers at UT Southwestern Medical Center
have designed a way to improve electrical stimulation of nerves by
outfitting electrodes with the latest in chemically engineered fashion:
a coating of basic black, formed from carbon nanotubes.

The nanotube sheathing improves the signals received and transmitted by
electrodes, which researchers say is a potentially critical step for
advancing electrical nerve stimulation therapy. This type of therapy
increasingly shows promise for diseases ranging from epilepsy to
depression to chronic leg and back pain.

By implanting electronic nerve stimulators, doctors elsewhere have
provided a quadriplegic patient with the ability to move a computer
cursor at will, and monkeys have been able to move objects in a virtual
world with mere mind power. For individuals who lose an arm or leg and
rely on prosthetics, implanted stimulators offer promise in restoring
feelings of sensation.

"The key to success for these types of brain-machine interfaces is where
the electrode meets the nerve tissue," said Dr. Edward Keefer,
instructor of plastic surgery at UT Southwestern and lead author of the
study appearing in a recent issue of Nature Nanotechnology. "When we
coat the electrodes with carbon nanotubes, it improves the stimulation
of the nerve and the feedback from the sensors."

Depending on the way the nanotubes are fashioned, researchers were able
to bolster either the stimulation or receptive capabilities to improve
performance. In some tests, the nanotube coating improved performance by
fortyfold, while in others it improved by a factor of as much as 1,600.

Nanotubes look like lattices rolled into a tube on a microscopic scale.
Although they are 1/50,000 the width of a human hair, nanotubes are
nonetheless among the stiffest and strongest fibers known, as well as
excellent conductors of electricity.

Those properties proved to be just the attributes needed to help
electrophysiologists conquer some of the hurdles facing them - issues
such as battery power and chemical stability.

The carbon nanotube coating improves conductivity, which means less
energy is needed to power the nerve stimulator. That can help reduce
routine maintenance, such as the need to change batteries in implanted
stimulation devices, as well as reduce tissue damage caused by the
electrical charge.

"Our process is like taking a Ford Pinto, pouring on this chemical
coating, and turning it into a Ferrari," Dr. Keefer said.

Researchers have tried several types of electrochemical coatings to see
if they could improve conductivity, but the coatings often break down
quickly or fail to stay affixed to the electrodes. The carbon nanotube
coating shows far more promise, although further research is still
needed, Dr. Keefer said.

"The development of new technologies by Dr. Keefer to potentially
restore function in wounded tissues and future transplantations is
exciting," said Dr. Spencer Brown, assistant professor of plastic
surgery who heads research in the Nancy Lee and Perry R. Bass Advanced
Plastic Surgery and Wound Healing Laboratory at UT Southwestern.