Biomedical Engineering Reference
In-Depth Information
different sizes, shapes and mechanical strengths can be generated to suit
specific applications. The potential of FDM fabricated PCL-based scaffolds
for regeneration of osteochondral defects (localised areas of joint damage
involving both the underlying bone and the overlying cartilage) has been
explored. Cao et al.
76
have investigated the co-culture of osteogenic and
chondrogenic cells on FDM-fabricated PCL scaffolds. Results in vitro showed
that both cell types proliferated, migrated and integrated at the interface,
but the final phenotype of the osteoblasts and chondrocytes within the PCL
scaffold were undetermined. This research indicates that FDM-fabricated
PCL scaffolds are not only biocompatible in vitro but have potential as
osteochondral constructs in tissue engineering. Hutmacher's group
77,78
has
investigated the potential of two types of hybrid scaffolds in vivo. In the first
hybrid design, fibrin served as a cartilage component whilst the FDM-fab-
ricated PCL scaffold served as the bone component.
77
Implantation of the
hybrid scaffolds into a rabbit model osteochondral defect showed that PCL
supports growth of mature trabecular bone; however, cartilage regeneration
was compromised due to rapid degradation of the fibrin glue matrix and the
consequent loss of mechanical support, required for the sustenance of the
newly formed immature cartilage.
77
The authors concluded that PCL scaf-
folds are a promising matrix for osteochondral bone regeneration, but fibrin
glue is not a suitable scaffold for the reconstruction of articular cartilage at
load-bearing sites.
77
Following the observations that fibrin glue is a poor cartilage substrate, a
second hybrid scaffold was created. FDM-fabricated PCL scaffolds served as
the cartilage component while PCL-TCP scaffolds comprised the bone
phase.
78
The hybrid scaffolds were implanted into osteochondral defects
within a rabbit model along with BMSCs and without BMSCs. Analyses of
tissues at 3 and 6 months after implantation indicated that BMSC groups
showed superior repair results compared to control groups.
78
With BMSC
implantation, the hybrid scaffolds provided su
cient support for new
osteochondral tissue formation. The bone regeneration was consistently
good from 3 to 6 months, with firm integration to the host tissue. The car-
tilage regeneration was more complicated; at 3 months, samples showed
formation of cartilage tissue around the PCL scaffold filaments.
78
However,
at 6 months, several samples revealed some degree of cartilage degradation
whilst others maintained a desirable appearance. Biomechanical tests
showed that the Young's modulus of the experimental group cartilage was
0.72 MPa. This was deemed noteworthy when compared with the 0.81 MPa
value of healthy cartilage.
78
In vivo viability of implanted cells was demon-
strated by the retention for 6 weeks in the scaffolds. This study demon-
strated that PCL-based hybrid scaffolds in combination with BMSCs could
be an alternative treatment for osteochondral defects in loading sites.
78
Both
of these studies by the Hutmacher group have demonstrated that FDM
fabricated PCL and PCL-TCP scaffolds have the potential to promote bone
healing. In the context of cartilage tissue engineering, PCL scaffolds per-
formed better than fibrin as the degradation rate of PCL is much lower and
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