Carbon nanotubes bridge nerve cells and electronics
14 November 2006
Carbon nanotubes that connect nerve cells to electronic circuits may lead
to new implantable biomedical devices that can act as artificial nerve
cells, control severe pain, or allow otherwise paralyzed muscles to be
Nicholas Kotov of the University of Michigan, USA, and colleagues have
used hollow, submicroscopic strands of carbon, carbon nanotubes, to connect
an integrated circuit to nerve cells. The new technology offers the
possibility of building an interface between biology and electronics. They
have published their results in Advanced Materials.
Kotov and colleagues at Oklahoma State University and the University of
Texas Medical Branch have explored the properties of single-walled nanotubes
(SWNTs) with a view to developing these materials as biologically compatible
components of medical devices, sensors, and prosthetics.
SWNTs are formed from carbon atoms by various techniques including
deposition and resemble a rolled up sheet of chicken wire, but on a tiny
scale. They are usually just a few nanometers across and up to several
micrometers in length.
The researchers built up layers of their SWNTs to produce a film that is
electrically conducting even at a thickness of just a few nanometers. They
next grew neuron precursor cells on this film. These precursor cells
successfully differentiated into highly branched neurons.
A voltage could then be applied, lateral to the SWNT film layer, and a
so-called whole cell patch clamp used to measure any electrical effect on
the nerve cells. When a lateral voltage is applied, a relatively large
current is carried along the surface but only a very small current, in the
region of billionths of an amp, is passed across the film to the nerve
cells. The net effect is a kind of reverse amplification of the applied
voltage that stimulates the nerve cells without damaging them.
Kotov and his colleagues report that such devices might find use in pain
management, for instance, where nerve cells involved in the pain response
might be controlled by reducing the activity of those cells. An analogous
device might be used conversely to stimulate failed motor neurons, nerve
cells that control muscle contraction. The researchers also suggest that
stimulation could be applied to heart muscle cells to stimulate the heart.
They caution that a great deal of work is yet to be carried out before
such devices become available to the medical profession.
1. Stimulation of Neural Cells by Lateral Currents in
Conductive Layer-by-Layer Films of Single-Walled Carbon Nanotubes. Advanced
Materials 2006, 18, No. 22.