Biomedical Engineering Reference
In-Depth Information
7.3.2 Applicaons
Because of the excellent chemical, physical, mechanical, biological and
electrical properties, CNTs have been widely studied for their application as
biomaterials.
7.3.2.1
Applicaons for bone ssue engineering
As CNTs are the strongest materials in the world, they can be used as agents
to obtain extremely high mechanical properties.
91,92
For example, 5% wt of
SWNTs signiicantly enhanced poly(vinyl alcohol)/ poly(vinyl pyrrolidone)/
sodium dodecyl sulphate (PVA/PVP/SDS) tensile strength,
93
and Shi
et al.
94
reported that the SWNTs, functionalised by covalent attachment with 4-
tert
-
butylphenylene groups were much better than pristine SWNTs in enhancing
the mechanical strength for poly(propylene fumarate)-CNT composite. Wang
and coworkers
95
obtained the biopolymer chitosan-MWNT nanocomposite
by a simple solution evaporation method. With the MWNTs homogeneously
dispersed throughout the chitosan matrix, the tensile modulus and strength
of the nanocomposites were improved by more than 90%. Therefore, CNTs
were often considered as reinforced bone tissue engineering scaffolds.
Adhesion of cells such as osteoblasts is a crucial prerequisite to subsequent
cell functions such as synthesis of extracellular matrix proteins and formation
of mineral deposits. Some research groups showed that CNT-based materials
appeared to be eficient as a nano-matrix for the nucleation and growth of
hydroxyapatite (HA), which is important for bone tissue engineering. Thus,
it is possible to design CNT-based materials as scaffolds with suitable surface
morphology for speciic cell adhesion and proliferation via the formed CNT/
HA layers.
Zanello
et al.
88
and Zhao
et al.
96
explored the application of CNTs as
scaffold materials for osteoblast proliferation and bone formation. SWNTs
showed that they could mineralise with hydroxyapatite. Biocompatible
studies indicated that, compared with other functionalised CNTs, pristine
CNTs and PEG-linked CNTs, which were neutral in charge, resulted in a
higher proliferation of osteoblast ROS 17/2.8 cells. Those cells were active
in producing HA crystals and responding to electric signals, thus suggesting
the biocompatibility of CNTs. These results, combined with CNTs' excellent
physical properties, promote CNTs as promising candidates to improve the
mechanical properties of damaged bone tissue.
Ultra-short CNTs (US tubes) were used to produce porous
nanocomposite scaffolds for bone tissue engineering.
97,98
Both original US
tubes and dodecylated US tubes could form porous structure with cavities
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