Biomedical Engineering Reference
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well assembled with molecular template(s), and the organic content of the
composite was about 12% to 20%, which was quite similar to the natural
bone in composition. The results revealed that the spatial structure of coas-
sembly template proteins played a pivotal role in controlling and regulating
HAp crystal nucleation and growth (Wang et al. 2011).
Preosteoblast MC3T3-E1 cells were cultured in hyaluronic acid-modified
chitosan/collagen/nano-hydroxyapatite (HAp-CS/Col/nHAp) composite
scaffolds and treated with phytoestrogen α-zearalanol (α-ZAL) to improve
bone tissue formation for bone tissue engineering. Osteogenic phenotype
increased or maintained enhanced collagen I (COLI) levels, decreased osteo-
pontin expression, and had little effect on osteocalcin expression during 12
days of in vitro culture. In response to α-ZAL, the cell-scaffold constructs
inhibited cellular proliferation, enhanced the alkaline phosphatase (ALP)
activity, and increased the ratio of osteoprotegerin to receptor activator of
nuclear factor kappa B (NF-κB) ligand (RANKL). Application of perfusion
and dynamic strain to cell-scaffold constructs treated with α-ZAL represents
a promising approach in the studies of osteogenesis stimulation of bone tis-
sue engineering (Liu et al. 2012).
The achievement of nanodistribution for inorganic reinforced filler is a
significant challenge to three-dimensional porous composite scaffolds. A
homogeneous nano hydroxyapatite/polyelectrolyte complex (HAp/PEC)
hybrid scaffold was developed and investigated. Based on the enhancing
properties of the formation of PEC between chitosan and hyaluronic acid,
the biocompatibility and bioactivity were evaluated by human bone mesen-
chymal stem cells (hBMSCs) proliferation (MTT assay), differentiation (alka-
line phosphatase [ALP] activity), and histological analysis. The in vitro tests
show that the scaffold is an excellent carrier for cell penetration, growth, and
proliferation for bone repair application (Chen et al. 2012).
7.2.1.1.2 Microspheres
Peng et al. (2010) reported a large scaffold 3 to 4 cm in length and 1 to 1.5 cm
in diameter designed for engineering large bone tissue in vivo . The scaffold
was made by filling HAp spherules, prepared by chitin sol emulsification in
oil and gelation in situ, into a porous HAp tube coated with a thin layer of
poly(L-lactic acid) (PLA) (Peng et al. 2010). Jevtic et al. (2009) obtained PLGA/
HAp biocomposite nanospheres via an ultrasound way. Optimal parameters
for the formation of PLGA/HAp included a lower content of the ceramic
phase (PLGA/HAp = 90:10), higher power of ultrasonic field (P = 142.4W),
lower temperature of the medium during ultrasonic treatment (T = 8°C),
dilute solution of PVP as surfactant and dispersion of HAp in polymer solu-
tion in order to achieve the desired homogeneity before the formulation of
the composite. The morphology of PLGA/HAp particles was highly uniform
and spher-like, with small dimensions (150-320 nm), highly uniform par-
ticle size distribution, and characteristics of planar spatial self-organization
(Jevtic et al. 2009).
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