Biomedical Engineering Reference
In-Depth Information
Fig. 9 Histology of PDLLA/BG scaffolds after 8 weeks of implantation in Sprague-Dawley rats
[
50
]. a PDLLA and b scaffold containing 20 wt% micron-sized BG stained with hematoxylin and
Factor VIII (brown rings). Scaffolds were well interspersed with newly formed tissue and blood
vessels. Key: black arrow: scaffold (opaque material), red arrow: blood vessel immunolocalized
for
Factor
VIII,
yellow
arrow:
cellular
infiltrate.
(Micrographs
taken
with
assistance
of
Dr T. Ansari's research group, Northwick Park Institute for Medical Research, UK)
complex mechanisms of angiogenesis. The scaffold microstructure also affects the
angiogenic response of the construct in vivo. Consequently, a ''dimension response
element'' has been suggested to be involved in the regulation of osteogenic and
angiogenic gene expression [
3
].
Recently, PDLLA/bioactive glass containing composite scaffolds (Fig.
8
)
have been fabricated, which exhibit high porosities high porosities (81-93%),
suitable permeability (k = 5.4-8.6 9 10
-9
m
2
) and compressive strength values
(0.4-1.6 MPa) in the lower range of trabecular bone [
50
]. After 8 weeks of
implantation, scaffolds containing m-sized BG and nano-sized BG were infiltrated
with newly formed tissue (Fig.
9
) and demonstrated higher vascularization and
percentage of blood vessel formation (11.6-15.1%) than neat PDLLA scaffolds
(8.5%). This work thus showed the potential for the regeneration of hard-soft
tissue defects and increased bone formation arising from enhanced vascularization
of PDLLA/bioactive glass constructs. Advanced functional bioactive glass scaf-
folds showing osteogenic and angiogenic properties, i.e., the ability to become
tightly attached to the host tissue, mineralized and vascularized, represent an
attractive solution for the regeneration of complex tissue structure defects, for
example at soft-hard tissue interfaces (e.g., the scaffold could be used as a ''plug''
at the cartilage-bone interface).
7 Conclusions and Future Work
One of the most significant challenges in bone tissue engineering remains the fab-
rication of scaffolds exhibiting mechanical, structural, surface-chemical, topo-
graphical and biological properties suitable for regenerating large (critical size)
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