Biomedical Engineering Reference
In-Depth Information
DNA ratio of ASCs was significantly higher in PLA/bioactive glass scaffolds
than in the other three scaffold types. These results indicate that the PLA/β-
TCP composite scaffolds significantly enhance ASC proliferation and total
ALP activity compared to other scaffold types (Haimi et al. 2009).
Yanoso-Scholl et al. (2010) investigated the microstructural and mechani-
cal properties of dense PLA and PLA/beta-TCP (85:15) scaffolds fabricated
using a rapid volume expansion phase separation technique, which embeds
uncoated β-TCP particles within the porous polymer. PLA scaffolds had
a volumetric porosity in the range of 30% to 40%. With the embedding of
β-TCP mineral particles, the porosity of the scaffolds decreased in half,
whereas the ultimate compressive and torsion strength were significantly
increased. When loaded with BMP2 and VEGF and implanted in the quad-
riceps muscle, PLA/beta-TCP scaffolds did not induce ectopic mineral-
ization but induced a significant 1.8-fold increase in neovessel formation
(Yanoso-Scholl et al. 2010). The biocomposite (PLA/β-TCP) was compared
with a currently used β-TCP bone substitute (ChronOS, Dr. Robert Mathys
Foundation) representing a positive control, and empty defects representing
a negative control. Ten defects were created in sheep cancellous bone, three
in the distal femur, and two in the proximal tibia of each hind limb, with
diameters of 5 mm and depths of 15 mm. Bone ingrowth was observed in
the biocomposite scaffold, including its central part. Despite initial fibrous
tissue formation observed at 2 and 4 months, but not at 12 months, this ini-
tial fibrous tissue does not preclude long-term application of the biocom-
posite, as demonstrated by its osteointegration after 12 months, as well as
the absence of chronic or long-term inflammation at this time point (Van
der Pol et al. 2010). Haaparanta et al. (2010) applied freeze-drying fabricating
porous PLA/β-TCP composite scaffolds to characterize these graded porous
composite scaffolds in two different PLA concentrations (2 and 3 wt%). Also,
three different β-TCP ratios (5, 10, and 20 wt%) were used to study the effect
of β-TCP on the properties of the polymer. The characterization was carried
out by determining the pH, weight change, component ratios, thermal sta-
bility, inherent viscosity, and microstructure of the scaffolds in 26 weeks of
hydrolysis. We observed that the fabrication method improved the thermal
stability of the samples. The dense surface skin of the scaffold may inhibit
the ingrowth of osteoblasts and bone tissue, while simultaneously stimulat-
ing the ingrowth of chondrocytes (Haaparanta et al. 2010). McCullen et al.
(2009) fabricated electrospun composite scaffolds consisting of β-TCP c r ys -
tals and poly(L-lactic acid) (PLA) at varying loading levels of β-TCP (0, 5, 10,
20 wt%). With the addition of β-TCP, the fiber diameter increased with each
treatment ranging from 503.39±20.31 nm for 0 wt% β-TCP to 1267.36±59.03
nm for 20 wt% β-TCP. The overall tensile strength of the neat scaffold (0 wt%
β-TCP) was 847±89.43 kPa; the addition of β-TCP significantly decreased this
value to an average of 350.83±38.57 kPa. DNA content increased in a tempo-
ral manner for each scaffold over 18 days in culture, although day 12 and the
10 wt% TCP scaffold induced the greatest hASC proliferation. Endogenous
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