Biomedical Engineering Reference
In-Depth Information
properties, CNTs have also been used as electrodes to stimulate neurons.
CNTs were seen to form tight contacts with neuron cell membrane that might
favour electrical shortcuts between the proximal and distal compartments
of the neurons, thus altering their electrophysiological responses. Therefore,
understanding the mechanisms at the origin of the effects of CNTs on neuronal
cells is essential for designing functional neuronal circuits.
With regard to other materials or devices used for applications in
neuroscience, CNTs show great potential as they possess a unique set of
physical, chemical, mechanical and electronic properties.
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A promising
substrate candidate suitable for neuronal growth requires several
characteristics, such as light weight, tight binding with neurons, controllable
branching of neurites and directed neuron network formation. It should also
ensure long-term cell viability. Besides, the combination of high electrical
conductivity, corrosion resistance, nanoscale size, strength and lexibility is
essential for neuroprosthetic devices for electrical recording and stimulation.
CNTs can meet these requirements because of their dimension, high electrical
conductivity and biocompatibility. Furthermore, CNTs have the exceptional
characteristic to be highly lexible, while being very strong. The properties
of CNTs can be, in part, transferred into CNT composites. CNTs are relatively
chemically inert, but the possibility of functionalising the nanotube surface
offers opportunities to tune their properties. Compared with other devices
or materials, CNTs have led to very promising results. Indeed, it has been
demonstrated that CNT-based substrates can serve as an extracellular scaffold
with a higher capability of directing neurite outgrowth and regulating neurite
branching than other types of substrates such as PLL, PEI or PLO, as explained
in part 6.2. In terms of recording and stimulating neuronal activity, CNT-based
electrodes exhibited better performances because of higher signal-to-noise
ratio, longer lifetime and higher tissue-electrode interface in comparison
with conventional commercial electrodes.
In terms of future potential applications, CNTs are promising candidates
for neural prostheses for restoring the function of damaged neuronal
circuits. CNTs could serve as an extracellular scaffold to guide neurite
outgrowth governed by their tips and growth cones, and also to regulate
neurite branching. These processes would lead to the re-establishment of
intricate connections between neurons forming synapses. CNTs could be
used to selectively enhance neurite elongation directly at the site of nerve
injury to aid in nerve regeneration, thus increasing the chance of connecting
the injured sites to sustain functional recovery. Several neurological
disorders and injuries, such as Parkinson's disease, epilepsy and stroke,
require an implantable device to generate electrical activity in the damaged
or diseased tissue.
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