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Nanotubes shown to boost neuron signals



R. Colin Johnson <rcj@spiritone.com>
EE Times
<www.eetimes.com/;jsessioni...0CJUNN2JVN>
(12/29/2008 1:00 PM EST)

PORTLAND, Ore. ? A team of researchers in Italy and Switzerland found
carbon nanotubes to be a biocompatible material that can be attached to
specific neurons to enhance their natural signal-processing capabilities.

"Our findings show that carbon nanotubes, which are as good an electrical
signal conductor as the nerve cells of our brain, form intimate mechanical
contacts with the cellular membranes, establishing a functional link to
neuronal structures," said University of Trieste (Italy) professor Laura
Ballerini.

Many studies over the last few years have demonstrated that carbon nanotubes
can improve the health of neural networks by promoting cell attachment,
differentiation and growth.

But the current report is the first to provide an experimentally supported
explanation for how carbon nanotubes enhance the efficacy of neural signal
transmission. Namely, that they form a mechanical and electrical
superstructure which enhances the natural function of individual neurons.

A neuron works by summing together inputs from its network of dendrites
connected to other neurons. When the sum exceeds a threshold, the neuron
fires a signal down its output axon, which is in turn connected to the
dendrites of other neurons. Together these networks of neurons process the
signals coming into the nervous system, then provide output signals to
stimulate the biological functions that support life and locomotion in
organisms.

When neurons become dysfunctional, due to disease or accidental damage, they
can sometimes be externally stimulated, for instance in tremor reduction for
Parkinson disease. However, the current results explaining the
biocompatibility of carbon nanotubes hold the promise of enabling permanent
repairs to be made to the faulty neurons, enhancing the performance of these
networks and restoring their original functions.

"This discovery considerably widens the perspectives of employing conductive
nanomaterials for neuroengineering applications, thus proposing carbon
nanotubes not only as ideal probes for bidirectional interfaces in
neuroprosthetics, but also as nanotools to endogenously re-engineer
single-neuron excitability and network connectivity," said Ballerini. "We
propose that due to the interaction among carbon nanotubes and neurons, the
efficacy in neural signal transmission is enhanced, thus carbon nanotubes
reengineer neuronal integrative properties."

The researchers propose engineering carbon nanotube scaffolds as electrical
bypass circuitry, not only for faulty neural networks but potentially to
enhance the performance of healthy cells to provide "superhuman" cognitive
functions. However, many engineering hurdles remain to realizing the
potential of augmenting neural networks with carbon-nanotube circuitry,
including stabilizing the mechanical interfaces between nanotubes and
neurons, determining which signal-sites to record from, which sites to
stimulate, and just what kind of signals will affect repairs or improve
cognitive functions.

Eventually, the researchers hope that carbon nanotube-based circuitry will
enable brain-machine interfaces for neuroprosthetics that process sight,
sound, smell and motion. Such circuits could, for instance, veto epileptic
attacks before they occur, perform spinal bypasses around injuries, and
repair or enhance cognitive functions.

The work was performed in the Laboratory of Neural Microcircuitry at the
Swiss Federal Institute of Technology (Lausanne, Switzerland) and was led by
Michel Giugliano, now a professor at the University of Antwerp (Belgium)
along with Ballerini and a dozen other research professors.