BIOMEDICAL APPLICATIONS V: INFLUENCE OF CARBON NANOTUBES IN NEURONAL LIVING NETWORKS - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 170

later. 62 Bianco et al. pointed out that this difference may be explained by the
different types of treatment carried out on the CNTs (i.e., puriication and
functionalisation with different chemical groups). Thus, these data indicated
that differently functionalised CNTs can have different impacts on neuronal
activity, thereby highlighting the importance of determining the inluence of
the functionalisation of CNTs.
6.4 INVESTIGATION OF THE MECHANISMS OF THE ELECTRICAL
INTERACTIONS BETWEEN CNTS AND NEURONS
Numerous studies have demonstrated that CNTs can sustain and promote
neuronal electrical activity in networks of cultured neuronal cells. But
the mechanisms by which they affect cellular function are still poorly
understood. Little is known about the details of the interactions between
CNTs and neurons. A few studies investigating possible hypotheses have been
recently reported.
In vitro models have been developed to investigate the electrophysiological
properties of synapses, neurons and networks coupled to CNTs, and to study
the electrical interactions between CNTs and membranes. Ballerini and
coworkers reviewed various existing experimental in vitro , in vivo and in silico
models of neuronal network and compared them by listing their advantages
and disadvantages. 3a The effects of CNT substrates on the electrical behavior
of brain networks in vitro were reported for the irst time.
Studies on the interface between neurons and SWNTs were performed
recently by Ballerini and coworkers. They focused on the electrical signal
transfer and the synaptic stimulation in cultured brain circuits. 63 Computer
simulations were included in the study to model the electrical interactions
between neurons connected via SWNTs. The results, strengthened by the
modelling of the CNT-neuron junction, showed that SWNTs can directly
stimulate brain circuit activity.
In this study, rat hippocampal cells were grown on a ilm of puriied SWNTs,
via deposition of functionalised SWNTs and subsequent defunctionalisation.
Patch-clamp experiments were then performed to determine the neuronal
responses to voltage steps delivered via conductive SWNT glass coverslips.
The morphology of the neuronal network was determined by SEM and
quantiied by immunocytochemistry analysis. SEM conirmed the adhesion
and growth of hippocampal neurons on SWNT substrates, accompanied
by variable degree of neurite extension. The attachment and proliferation
processes were similar to those observed for neuronal growth on control glass