Biomedical Engineering Reference
In-Depth Information
In summary, this study reported that SWNTs might affect neuronal
information processing. Indeed, the action potential backpropagation was
substantially enhanced in neurons grown on SWNT substrates. However,
the exact mechanisms at the origin of this effect are not totally clear. One
hypothesis relies on the discontinuous and tight interactions between SWNTs
and neuronal membranes.
Finally, following their study on neuronal growth on CNT substrates,
Haddon and coworkers investigated the mechanism by which CNTs induce
extension of neurite length.
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They demonstrated that water-soluble SWNTs
are able to inhibit stimulated membrane endocytosis in neurons. Following
the observation that water-soluble SWNTs modiied Ca
2+
dynamics in
neurons, thus leading to a decrease of the depolarisation-dependent inlux
of Ca
2+
during cell stimulation, the authors investigated the effect of water-
soluble SWNTs on membrane recycling. Indeed, the plasma membrane/
vesicular recycling inluences the extension of neurites
65
and is regulated by
an inlux of Ca
2+
from the extracellular space induced by the depolarisation
of neurons.
In this study, hippocampal neuronal cultures were treated with SWNT-
PEG. The neurons were exposed to FM1-43 [
N
-(3-triethylammoniumpropyl)-
4-(4-(dibutylamino)styryl)pyridinium dibromide],
66
a luorescent dye
that can monitor membrane recycling and that is internalised into cells by
endocytosis as it does not passively diffuse across cell membranes. With regard
to the constitutive vesicular recycling, taking place in unstimulated cells, the
water-soluble graft copolymer SWNT-PEG had no effect on the endocytosis of
FM1-43. However, in stimulated neurons (using HIK
+
), the pegylated SWNTs
reduced the endocytotic loading of FM1-43 in a dose-dependent way.
In summary, the mechanism responsible for the effects of water-soluble
SWNTs on enhancement of selected neurite outgrowth was elucidated.
The pegylated SWNTs inhibited regulated/stimulated plasma membrane/
vesicular recycling, while the constitutive phenomenon was unaffected.
6.5 CONCLUSIONS AND PERSPECTIVES
CNTs have been demonstrated as a biocompatible substrate that promotes
neuronal growth, boosts neural activity and transmits electrical stimulation
effectively. Indeed, many studies reported the use of CNTs as substrate to
promote neuronal cell adhesion and to induce growth and differentiation of
neurons. Functionalisation of CNTs can modulate some processes, such as the
outgrowth and branching of neurites. In particular, the surface charge was
found to have a strong effect on neuronal growth. Because of their electrical
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