Biomedical Engineering Reference
In-Depth Information
nHAp content increased from 0 to 50 wt%. They claim that these scaffolds
should be suitable materials
for non-load-sharing tissue engineering
applications.
More recently, Wang et al. (2010b) examined the in vitro response of
porous nano-hydroxyapatite/polycaprolactone (nHAp/PCL) scaffolds.
After 7 days of culture, the bone marrow stromal cells (BMSCs) coalesced
to form a large and flat layer of cells and cover on the nHA/PCL scaffold,
while they presented as clusters or agglomerates on the PCL scaffold. The
poor cell growth on the PCL scaffold is probably due to its hydrophobicity,
which may interfere in the cell attachment. These results suggest that nHA/
PCL scaffolds could be promising in bone tissue engineering. Moreover,
Nejati et al. (2009) compared the cell affinity and cytocompatibility of
mesenchymal stem cells (MSCs) in nanoHAp and microHAp PCL
composites. They stated that cell proliferation was higher in the
nanocomposite, which was attributed to the larger surface area of nHAp,
proving superior cell viability and cytocompatibility of the nanocomposite.
Wang et al. (2010a) synthesized a new silane-modified nano-HAp
(mnHAp) in order to improve the interfacial connection of HAp to
PLLA. Characterization of the composite scaffold showed that mnHAp was
homogeneously distributed in the scaffold. As a result, the compressive
modulus and protein adsorption of PLLA/mnHAp (80:20 w/w) composite
scaffold increased 4.2-fold and 2.8-fold compared with those of a pure
PLLA scaffold. Incorporating mnHAp into PLLA network also buffered
the pH reduction and reduced weight
loss
in in vitro degradation
significantly.
These nano-hydroxyapatite composites show higher mechanical proper-
ties and better cell behaviour than conventional polymeric scaffolds. Their
ceramic counterparts are bioactive, but show very low biodegradation rates.
Furthermore, if bioresorbable ceramics such as biphasic calcium phosphate
(BCP) and bioglass are used for the repair of bone, reconstruction could be
more rapid (Habraken et al., 2007; Migliaresi et al., 2007).
BCP possesses sufficient degradation, excellent biocompatibility, osteo-
conductivity, and even osteoinductivity (Yuan and Groot, 2005).
Ebrahimian-Hosseinabadi et al. (2011) recently fabricated PLGA/nano-
biphasic calcium phosphate (nBCP) composite scaffolds. The size of the
nanoparticles was estimated to be less than 100 nm. The elastic modulus and
yield strength of the nanocomposite scaffold were significantly enhanced,
showing the highest values with 30%wt of the nanopowder. Moreover,
from the biodegradability point of view, the authors state that by increasing
the amount of nBCP particles in the PLGA/nBCP scaffolds, hydrophilicity
increases and causes a larger weight loss.
Some bioactive glasses can directly bond to living bone without the
formation of surrounding fibrous tissue. In such cases, a bone-like apatite
