Biomedical Engineering Reference
In-Depth Information
high electrical conductivity of CNTs should enable the detection of neuronal
electrical activity and allow delivering electrical stimulation to neuronal cells
in contact with them.
In this chapter, we will present the use of CNTs as substrates for neuronal
growth, favouring adhesion of neurons and their survival, growth and
differentiation in neurites. We will also detail the use of CNTs to electrically
stimulate neuronal cells as well as the inluence of CNTs in promoting
spontaneous synaptic activity in neuronal networks and in increasing the
eficacy of neural transmission. We will then close this chapter by reporting
the studies that investigated the mechanisms of the electrical interactions
between CNTs and neurons.
6.2 EFFECTS OF CARBON NANOTUBES ON NEURONAL
CELLS' ADHESION, GROWTH, MORPHOLOGY AND
DIFFERENTIATION
As it will be described in this part, numerous studies have revealed that
CNTs can support and control the growth of neuronal cells as well as their
morphology. SWNTs and MWNTs have been found to be permissive substrates
for neuronal growth characterised by the presence of growth cones, neurite
outgrowth and branching.
The irst use of CNTs as substrates for nerve cell growth was reported
by Mattson and coworkers. 5 In this study, embryonic rat hippocampal
neurons were grown on MWNTs dispersed on glass coverslips coated with
polyethyleneimine (PEI), which is a common substrate for neuronal growth. 6
Neurons require highly permissive substrates for cell attachment and neurite
growth, which include positive-charge modiication of glass and plastic
culture substrates (e.g., polylysine or polyornithine [PLO]) 7 for optimum
growth and neurite extension.
Two types of MWNTs were utilised to investigate neuronal growth: pristine
MWNTs and MWNTs coated with 4-hydroxynonenal (4-HNE), a molecule
that effects neurite growth. 4-HNE is known for its ability to regulate neurite
outgrowth in cultured embryonic hippocampal neurons 8 via modulation of
intracellular Ca 2+ levels in cultured hippocampal neurons. 9 Physisorption of
4-HNE on the MWNT surface was achieved by sonicating MWNTs in an acidic
solution of 4-HNE. Mattson et al. observed that neurons grown on MWNTs
survived and continued to grow for at least eight days in culture, indicating
that MWNTs support long-term neuronal survival and provide a permissive
substrate for neurite outgrowth. It was observed that the direction of growth
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