Biomedical Engineering Reference
In-Depth Information
(Fig. 10.5). Carbon nanotubes are prepared using arc-discharge
[28], laser ablation [55], and chemical vapor deposition [11]. In the
CVD process, the carbon nanotubes are grown using metal catalysts,
such as nickel, so the growing nanotubes could be cytotoxic [21].
Thus, a puriication step is usually required before carbon nanotubes
can be used for biomedical applications. Reluxing carbon nanotubes
in an oxidizing acid (for example nitric acid) is one of the most
commonly used puriication method [21]. This process oxidizes and
removes the metal catalysts and carbonaceous deposits from the
inside and outside of the tube.
Figure 10.5
Scanning electron micrographs of multi-walled carbon
nanotubes [21].
l
in vitro
studies report that carbon nanotubes are cytotoxic
[27, 44, 51]. However it was also reported that they improve neural
signal transfer and support dendrite elongation and cell adhesion
in vitro
[42] and also support the smooth muscle [43], ibroblasts
[13], and osteoblast as well [53]. The purity of nanotubes plays an
important role in cytotoxicity, and functionalization of nanotubes
with glycopolymers can lead to the diminishing of their cytotoxicity
[48].
In recent years, the number of articles related to carbon nanotubes
for use in biomedical applications, including tissue engineering, has
doubled each year (Fig. 10.6) [21].
Carbon nanotubes can be used in bone tissue engineering, for
example, for the enhancement of polymer and ceramic composites
and for nanostructured coatings to improve the bioactivity of the
implant surfaces [52]. The bone tissue is composed of nanoscale
inorganic crystals, containing calcium, phosphate ions, and collagen
ibrils with diameters ranging 20-40 nm [54]. The nanoscale
