BIOMEDICAL APPLICATIONS V: INFLUENCE OF CARBON NANOTUBES IN NEURONAL LIVING NETWORKS - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 168

Gabriel et al. reported an alternative and simple method to fabricate CNT-
based MEAs. 57 A suspension of puriied SWNTs produced by arc discharge
was deposited onto platinum electrodes. 58 This method has the advantage
to be a post-process procedure that can be used with almost any MEA. The
electrical properties of the CNT-based MEAs were found to be superior to
those of metal electrodes, as shown by in vitro impedance and electrochemical
characterisation. To investigate the biocompatibility of the CNT-based
electrodes, in vitro cytotoxicity tests were carried out with different cell
types from the nervous system: neurons (PC12 cells), glial cells (42MG-BA
cells), ibroblasts (3T3 cells) and endothelial HEK cells (293T cells). The
cell activity, estimated by the MTT assay, was not affected by the presence of
CNTs, and no signiicant decrease in proliferation was detected. In addition,
the SWNTs did not display any toxicity and remained attached to the surface
of the electrode. Extracellular ganglion cell recordings in isolated superfused
rabbit retinas were performed to evaluate the capacity of the CNT-based
MEAs. It was the irst time that CNTs were used to record electrophysiological
activity in cultured retinal explants. The results indicated that the SWNT MEA
arrays were more eficient in recording the action potential generated by a
population of ganglion cells than Pt electrodes.
The effect of MWNTs functionalised with cell-adhesion peptides on
neuronal functionality was recently investigated by Bianco et al. 59
In this study, MWNTs were functionalised via 1,3-dipolar cycloaddition
of azomethine ylides, and the resulting pyrrolidine ring was derivatised
with two peptides, one including the cell-binding domain RGD sequence
(GRGDSP) and the other comprising a domain of the laminin protein (IKVAV),
as illustrated in Scheme 6.3. GRGDSP is a ibronectin-derived peptide capable
of promoting cell adhesion and neurite outgrowth. RGD-containing peptides
are also involved in the mechanism of integrin regulation of neuronal gene
expression. 60 Besides, peptides from different domains of laminin were used
to stimulate neuronal growth and axon regeneration. 61
The activity of the two peptide-nanotube conjugates on different types
of cells, including tumour cells (Jurkat), primary splenocytes and neurons,
was examined. Upon incubation of Jurkat cells with increasing doses of the
peptide-nanotube conjugates (up to 100 μg/mL), low cytometry showed no
signiicant loss of cell viability. Similarly, no cytotoxic effect of the peptide-
nanotube conjugates on splenocytes isolated from healthy BALB/c mice was
observed, thus highlighting the biocompatibility of the functionalised MWNTs.
Furthermore, doubly functionalised peptide-nanotube conjugates containing
FITC were prepared and found to be internalised into the neuronal cells.