BIOMEDICAL APPLICATIONS II: INFLUENCE OF CARBON NANOTUBES IN CANCER THERAPY - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 77

showed a well-deined anodic peak at the modiied electrode, while no peak
was observed when a bare electrode was used. It was proved that the anodic
peak current increases at a higher concentration of MWCNTs, demonstrating
an electron transfer effect for nanotubes, but concentrations higher than 4
mg/mL tend to render the cell membrane unstable. 89 Also in this case the
anodic peak is due to purine nucleobase oxidation, especially guanine. The
experiments proved that the peak current is strictly related to cell number
and to guanine expression in the cytoplasm. In fact, in the presence of the
anticancer drugs, which inhibit the growth and viability of cells, this signal is
signiicantly decreased, demonstrating the possibility of using voltammetry
to evaluate antitumour drug sensitivity .
The use of electrochemistry implies many advantages with respect to
conventional techniques considering that these systems are cheaper and less
time-consuming and present wide possibilities in signal ampliication with a
higher sensitivity.
Other authors, too, screened anticancer drugs by means of sensors.
Ovádeková et al. modiied a screen-printed electrode for the detection of
dsDNA by employing MWCNTs, gold nanoparticles (GNPs) and a mixture of
the two. Calf thymus dsDNA was introduced with layer-by-layer deposition or
by using a mixed coverage. The latter methodology allowed for obtaining more
intense responses than layer-by-layer deposition on the GNP- or MWCNT-
modiied electrode. The authors used this device to detect the activity of
different antitumour drugs interacting with DNA, including berberine, a DNA-
intercalating alkaloid. The signal decrease was found to be dependent on the
concentration of the compound. Moreover, since this drug is quite effective at
discriminating between cancer and non-cancer DNA, because of the presence
of permanently open loops in tumour cells' DNA, it represents an interesting
way to distinguish cancer cells from healthy cells. 90
3.8 CONCLUSIONS
More efforts are needed to validate the possibility of using carbon nanotubes
as drug carriers for cancer treatment in chemotherapy, in photothermal
ablation and in radiotherapy. Biocompatibility and toxicity are issues to be
addressed in detail, but these irst studies are showing very promising results
for potential applications in the ield of nanomedicine. On the other hand,
biosensing has been giving really important results and is not constrained by
the need to assess the toxicity of this novel nanomaterial; therefore, it has a
tremendous scope for development.