Biomedical Engineering Reference
In-Depth Information
coat substrates to promote cell adhesion and neurite outgrowth.
50
The SWNT-
laminin ilms were heat-treated to increase their electrical conductivity by
enhancing the cross-linking of CNTs among the different layers of the ilms
prepared by LBL. Cell adhesion was clearly seen to depend strongly on the
composition of the inal layer of the LBL ilms. Indeed, the ilm containing
SWNTs as top layer was the most suitable for cell adhesion and attachment.
Differentiation of NSCs was observed, as indicated by extensive formation of
functional neuronal network showing the presence of synaptic connections.
By comparison with laminin-coated substrates, longer neuronal outgrowth
occurred on the SWNT-laminin substrates that were found to be biocompatible,
as indicated by satisfactory cell viability assays. The functionality of the
neuronal networks was assessed by immunostaining for the presence of
synapsin protein with the above-mentioned neuronal markers. Synapsin
was present between the differentiated cells. This indicated that neuronal
network was functional. The electrical stimulation of NSCs by the SWNT-
laminin ilms was then investigated. Cell response to chemical and electrical
stimuli typically results in a change in the membrane voltage of the cells,
referred to as action potential. Detection of action potentials can be achieved
via the invasive patch-clamp method.
51
The generation of action potentials
upon the application of a lateral current through the SWNT ilm was deduced
from the imaging of the NSCs with a Ca
2+
-dependent dye and was found to be
dependent on the status of the surrounding cells. Once one neuronal cell was
excited, the excitation sequentially spread from one cell to another.
In summary, the combination of different properties of the SWNT/laminin
thin ilm makes them a promising candidate for incorporation in neural
electrodes. On the one hand, the ilms were suitable for NSCs' growth and
proliferation. On the other, as SWNTs exhibit high electrical conductivity, they
were able to electrically stimulate NSCs.
Chen
et al.
have been the irst to explore the interface between neurons
and CNT probes, both extracellularly and intracellularly (i.e., inside the neural
membrane).
52
CNT probes were used to monitor the neuronal activity elicited
not only extracellularly but also intracellularly. This work is particularly
interesting as it opens the way for intracellular neural probes that minimise
damage to the neuron.
In this study, two types of CNT probes were fabricated. MWNT bundles
were connected to a silver wire. In one case, CNTs were coated with insulating
epoxy, while in the other, CNTs were inserted into a sharp glass pipette, whose
tip was used to penetrate the neural membrane. Only the tips of the probes
were made of CNTs, contrary to the CNT-coated microelectrodes that were
also involved in interfacing neurons.
41,42,53
The CNT probes were examined
with the escape neural circuit of crayish (
Procambarus clarkia
) and were
Search WWH ::
Custom Search