Biomedical Engineering Reference
In-Depth Information
interconnected.
In vitro
studies showed that the porous materials provided
substrates for marrow stromal cells' attachment and proliferation, suggesting
good osteoconductivity.
97
When the US tubes were used as reinforcing
scaffold and tested in an
in vivo
rabbit model, they exhibited favourable hard
and soft tissue responses at different time points.
98
Bone tissue growth in
US-tube-based materials was many times greater than that in poly(propylene
fumarate), which was used as control. Moreover, US tubes caused fewer
inlammatory effects on the tissue.
CNTs can serve as a template for the ordered formation of a nanostructured
HA layers for tissue engineering. Boccaccini and coworkers
99
prepared
bioglass-based tissue scaffolds for bone tissue engineering. Electrophoretic
deposition (EPD)
100
was used to deposit CNTs on planar substrates and form
porous layers. The CNT scaffolds were bioactive for the formation of HA.
CNTs in these scaffolds functioned as templates for nucleation and growth of
the HA nanosize crystals and could completely be embedded in the HA layer.
Therefore, by coating CNTs it was possible to improve the bioglass-based
scaffolds' performance in bone tissue engineering applications.
CNTs were often associated with other polymers to achieve novel properties
and overcome several disadvantages intrinsically present in polymers. Mei
et
al.
101
reported the synthesis of poly(-lactic acid) MWNTs and hydroxyapatite
(PLLA/MWNT/HA) composite membrane by the electrospinning technique.
The materials showed selectivity for adhesion and proliferation of different
cells. The PLLA/MWNT/HA membrane enhanced the adhesion and
proliferation of periodontal ligament cells (PDLCs) by 30% and inhibited the
adhesion and proliferation of gingival epithelial cells by 30%. The selectivity
may be due to the higher surface energy of the nanostructured surface, which
would enhance the adhesion of osteoblast cells and inhibit the adhesion of
osteoblast competitive cells.
102,103
Bacakova
et al.
104
designed a terpolymer-
CNT composite. The substrate composed of polytetraluoroethylene,
polyvinyldiluoride, polypropylene and CNTs showed enhanced compatibility
for cell spreading. Cells grown on the terpolymer-CNT substrate showed
higher activity and proliferation.
Bone morphogenetic protein could assist the growth of bone on CNTs. Usui
and coworkers
105
incubated recombinant human bone morphogenetic protein-
2 (rhBMP-2) with collagen and MWNTs. The MWNTs may accelerate bone
formation, and histological studies found that immature bone conspicuously
surrounded MWNTs at an early stage. The bone mineral content (BMC) in
rh-BMP-2/MWNT/collagen sample was higher than in the control, which did
not contain MWNTs. Although the difference was not signiicant, the result
suggested that MWNTs are biocompatible for bone formation.
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