GALVESTON, Texas --Texas scientists have added one more trick to the amazing
repertoire of carbon nanotubes -- the ability to carry electrical signals to
nerve cells.
Nanotubes, tiny hollow carbon filaments about one
ten-thousandth the diameter of a human hair, are
already famed as one of the most versatile materials
ever discovered. A hundred times as strong as steel
and one-sixth as dense, able to conduct electricity
better than copper or to substitute for silicon in
semiconductor chips, carbon nanotubes have been proposed
as the basis for everything from elevator cables
that could lift payloads into Earth orbit to computers
smaller than human cells.
Thin films of carbon nanotubes deposited on transparent
plastic can also serve as a surface on which cells
can grow. And as researchers at the University of
Texas Medical Branch at Galveston (UTMB) and Rice
University suggest in a paper published in the May
issue of the Journal of Nanoscience and Nanotechnology,
these nanotube films could potentially serve as an
electrical interface between living tissue and prosthetic
devices or biomedical instruments.
"As far as I know, we're the first group to show
that you can have some kind of electrical communication
between these two things, by stimulating cells through
our transparent conductive layer," said Todd Pappas,
director of sensory and molecular neuroengineering
at UTMB's Center for Biomedical Engineering and one
of the study's senior authors. Pappas and UTMB research
associate Anton Liopo collaborated on the work with
James Tour, director of the Carbon Nanotechnology
Laboratory at Rice's Richard E. Smalley Institute
for Nanoscale Science and Technology, Rice postdoctoral
fellow Michael Stewart and Rice graduate student
Jared Hudson.
The group employed two different types of cells
in their experiments, neuroblastoma cells commonly
used in test-tube experiments and neurons cultured
from experimental rats. Both cell types were placed
on ten-layer-thick "mats" of single-walled carbon
nanotubes (SWNTs) deposited on transparent plastic.
This enabled the researchers to use a microscope
to position a tiny electrode next to individual cells
and record their responses to electrical pulses transmitted
through the SWNTs.
In addition to their electrical stimulation experiments,
the scientists also studied how different kinds of
SWNTs affected the growth and development of neuroblastoma
cells. They compared cells placed on mats made of "functionalized" SWNTs,
carbon nanotubes with additional molecules attached
to their surfaces that may be used to guide cell
growth or customize nanotube electrical properties,
to cells cultured on unmodified "native" carbon nanotubes
and conventional tissue culture plastic.
"Native carbon nanotubes support neuron attachment
and growth well -- as we expected, better than the
two types of functionalized nanotubes we tested," Pappas
said. "Next we want to find a way to functionalize
the nanotubes to make neuron attachment and communication
better and make these surfaces more biocompatible."
Another avenue Pappas wants to explore is finding
out whether nanotubes are sensitive enough to record
ongoing electrical activity in cells. "Where we want
to get to is a device that can both sense and deliver
stimuli to cells for things like prosthetic control," Pappas
said. "I think it's definitely doable, and we're
pursuing that with Jim Tour and his group. It's great
to be able to work with a guy who's on the cutting
edge of nanoelectronics technology -- he seems to
develop something new every week, and it's really
become a great interaction."
The University of Texas Medical Branch at Galveston
Public Affairs Office
301 University Boulevard, Suite 3.102
Galveston, Texas 77555-0144
www.utmb.edu
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