Biomedical Engineering Reference
In-Depth Information
iodine-125-labeled SWNTs were injected into mice. They were shown to be
distributed throughout the whole body, except the brain, and accumulated
in bone.
158
However, a contradictory result was reported by Singh et al. who
administered diethylenetriaminepentaacetic acid-functionalized SWNTs,
labeled with indium-111, into the bloodstream. A rapid clearance rate and
no retention of the SWNTs in any of the secondary organs, such as the liver
or the spleen, was observed. The SWNTs were excreted as intact nanotubes
through the renal excretion route.
168
Another possible solution for visualiza-
tion of CNT distribution can be the use of gadolinium-labeled CNTs, as pro-
duced by Sitharaman et al.
89,90
in an MRI experiment. Blending these labeled
CNTs in a degradable bone tissue-engineered construct, followed by implan-
tation in an animal model, gives the opportunity to follow the labeled CNTs
over time by MRI (Figure 4.9).
(a)
Gadolinium
1
11
7
18
25
(b)
FIGURE 4.9
(a) Molecular representation of a functionalized SWNT with gadolinium as contrast agent, and
(b) magnetic resonance imaging slices of subcutaneously implanted PLGA scaffold containing
such gadolinium-labeled SWNTs on days 1, 7, 11, 18, and 25. Marking on day 1 slide indicates
the scaffold and marking on day 18 slide indicates the tissue surrounding the scaffold that has
increased intensity due to released SWNTs after degradation of the scaffold.
