Biomedical Engineering Reference
In-Depth Information
(a)
(b)
FIGURE 4.6
(a) Single-walled and (b) multiwalled CNTs.
(a)
(b)
RU
SEI
3.0 kV
×20,000
1 µm
WD 13.4 mm
200 nm
FIGURE 4.7
(a) Scanning electron micrograph and (b) transmission electron micrograph of CNTs.
Until now, the most common functionalization for CNTs is to decrease their
hydrophobicity otherwise they tend to aggregate into bundles. Aggregated
CNTs are difficult to handle and also result in loss of function. 88 A study
by Shi et al. 82 demonstrated this by reporting on much better dispersion of
fluoride functionalized SWNTs throughout poly(propylene fumarate) (PPF)
scaffold materials resulting in increased reinforcement of the materials.
However, there are also other reasons for functionalizing CNTs. For instance,
functionalization with gadolinium has been shown to result in an excellent
contrast agent for magnetic resonance imaging (MRI). 89-91 In the near future,
it may also be interesting to functionalize the CNTs with biological agents,
in order to gain biocompatibility or osteoconductivity of scaffold materials
to prevent immune responses at the site of implantation, or to use the nano-
tubes as drug delivery systems.
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