BIOMEDICAL APPLICATIONS II: INFLUENCE OF CARBON NANOTUBES IN CANCER THERAPY - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 64

(DMSO) solution of a CNT derivative was used, the maximum boron
concentration in tumour tissues, achieved 16 hours after administration, was
27.9 μg boron/g(tissue). In the case of CNT in saline solution, the maximun
concentration of boron in tissue was lower (22.8 μg boron/g[tissue]) and it
was achieved after 30 hours. In both cases, the tumour-to-blood boron ratio
was favourable, with a much higher concentration in tumour cells than in the
bloodstream (the ratio was, respectively, 6.13 when DMSO was used and 3.12
when saline solution was used).
These results permit to seriously consider boron-CNT derivatives suitable
for BNCT.
3.6 CARBON NANOTUBES IN THERMAL ABLATION
A very interesting application of carbon nanotubes in cancer therapy can
arise from their intrinsic optical properties, which can be exploited to kill
cancer cells by photothermal destruction. In fact the optical absorbance of
this material is very high in the near-infrared region (NIR; 700-1100 nm),
while biological systems are transparent to these wavelengths.
It is worth noting that gold nanoshells and nanoparticles represent
the only other materials which gave good results in photothermal cancer
treatment with NIR radiation. 57-59 In these cases the laser intensity and
the radiation time used are often higher than those needed to kill cells in
experiments with nanotubes. From this observation it is evident that CNTs are
even more promising materials in the ield that can pave the way for further
explorations to reach the laser energy level of 35-45 mJ/cm 2 , established as
the safety standard for medical lasers. 60
Dai et al. presented the thermal application of CNTs in 2005 for the irst
time. 61 Compound 18 (Fig. 3.12) , where SWCNTs have been wrapped by
phospholipids linked to PEG chains bearing either a luorescent tag or a folic
acid moiety, was administered in vitro to normal HeLa cells (as a control) and
to HeLa cells overexpressing the folate receptor (FR + cells). The latter showed
a high internalisation of 18 , while little uptake was found in the normal cells.
The irradiation by an 808 nm laser (1.4 W/cm 2 ) for 2 minutes resulted in
an extensive death for cells internalising CNTs (FR + ones) and in normal
proliferation behaviour for FR - cells.
More recently, Shao et al . prepared a multi-component targeting system,
binding to SWCNTs two different monoclonal antibodies, speciic for
breast cancer cell antigens (IGF1R and HER2). The double targeting should
ensure higher eficacy and selectivity. Derivative 19 has been prepared by