Scientists have been studying how neuron communication
in the brain relies on glass and metal electrodes to detect the tiny, high
speed synaptic potentials. Yet, nanotechnology offers the possibility of
scaling down the electrodes so that individual neurons could be tapped in
living, moving animals. Researchers at Duke University are now claiming that
they developed electrodes made out of self-entangled carbon nanotubes that are
a millimeter long and feature a sub-micron tip. Carbon nanotubes have excellent
electrical properties and are incredibly strong for their size. The new needles
are small enough to penetrate individual cells and record intracellular
electrical activity. The Duke team used the new electrodes to make such
recordings in live animals and on brain slices and envision using the new
electrodes to record neuronal activity for extended periods in freely moving
animals.
The computational complexity of the brain
depends in part on a neuron’s capacity to integrate electrochemical information
from vast numbers of synaptic inputs. The measurements of synaptic activity that
are crucial for mechanistic understanding of brain function are also
challenging, because they require intracellular recording methods to detect and
resolve millivolt scale synaptic potentials. Although glass electrodes are
widely used for intracellular recordings, novel electrodes with superior
mechanical and electrical properties are desirable, because they could extend
intracellular recording methods to challenging environments, including long
term recordings in freely behaving animals. Carbon nanotubes (CNTs) can
theoretically deliver this advance, but the difficulty of assembling CNTs has
limited their application to a coating layer or assembly on a planar substrate,
resulting in electrodes that are more suitable for in vivo extracellular
recording or extracellular recording from isolated cells. Here a novel, yet
remarkably simple, millimeter-long electrode with a sub-micron tip, fabricated
from self-entangled pure CNTs can be used to obtain intracellular and
extracellular recordings from vertebrate neurons in vitro and in vivo. This
fabrication technology provides a new method for assembling intracellular
electrodes from CNTs, affording a promising opportunity to harness
nanotechnology for neuroscience applications.
