Biomedical Engineering Reference
In-Depth Information
Figure 9.10 3 H-PTX biodistribution in 4T1 tumour-bearing mice injected with 3 H-
labelled Taxol, PEG-PTX and SWCNT-PTX at 2 hours after injection. Reproduced from
Liu et al . 60 with permission. See also Colour Insert.
As a proof of that, a pilot toxicological study of CNTs was done on a small
number of mice: 64 functionalised SWCNTs were injected into the bloodstream
of mice, and no evidence of acute or chronic toxicity was observed over a
period of 4 months. For the same period, functionalised SWCNTs apparently
accumulated in liver and spleen macrophages, without affecting tissue
composition, as demonstrated by necropsy and histological evaluations.
These encouraging results were conirmed by biodistribution studies on
intravenously injected SWCNT-PEG complexes in various organs and tissues
of mice ex vivo over a period of 3 months. 65
Functionalisation of SWCNTs by branched PEG chains enabled thus far
the longest SWCNT blood circulation up to 1 day, with low uptake in the RES,
and near-complete clearance from the main organs in ~2 months. Raman
spectroscopy detected SWCNTs in the intestine, feces, kidney and bladder
of mice, suggesting excretion via the biliary and renal pathways. No toxic
side effect of SWCNTs to mice was observed, thus paving the way for future
biomedical applications of CNTs.
In another study on biodistribution, the authors investigated the effects
of radio-labelled SWCNTs in mice by in vivo positron emission tomography
(PET), ex vivo biodistribution and Raman spectroscopy [66]. In particular
SWCNTs, functionalised with phospholipids (PL) bearing PL-PEG chains
were used, determining a long blood circulation and a selective targeting
towards integrin-positive tumours, providing that SWCNTs were doped with
PEG chains linked to a cyclic arginine-glycine-aspartic acid (RGD) peptide
in the form of a multivalent system. The same complex, made up of SWCNTs
combined with RGD peptide, has shown the incredible property of acting as
a photoacoustic contrast agent, thus offering 8 times higher signal than non-
 
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