Biomedical Engineering Reference
In-Depth Information
CPC-alginate scaffolds underwent shrinkage in the x-, y-, and z-directions
to a different extent during drying due to the loss of water from alginate
pastes (Figure 4.10). Scaffolds printed from highly concentrated alginate also
undergo shrinkage to a certain degree but without deformation, in contrast
to scaffolds prepared from low-concentrated alginate sols that suffer from
severe shrinkage and deformation during drying. In case of the biphasic
CPC-alginate scaffolds, only the alginate strands shrunk and were thereby
stretched along the plotting direction; however, almost no shrinkage was
observed for the whole scaffold due to the support of CPC strands.
4.3.2 Characterization of the Plotted CPC-Alginate Scaffolds
To evaluate the potential of the novel biphasic CPC-alginate scaffolds, their
mechanical properties, cytocompatibility, and protein delivery ability were
studied
in vitro
in comparison to scaffolds plotted of pure P-CPC, pure 16.7
wt% alginate paste, and the mixed CPC-alginate paste.
The compressive strength and modulus of the plotted scaffolds in dry and
wet state (after incubation in simulated body fluid [SBF] for 2 h) were tested
by using an Instron 5566 device with a load cell of 10 kN and a constant rate
of 1 mm/min. The obtained results including compressive strength, modu-
lus, and stress-strain curves of the scaffolds are presented in Figure 4.12.
The compressive strength of both the biphasic CPC-alginate scaffolds and
the mixed CPC-alginate scaffolds was almost twice as high as that of pure
CPC ones in dry state. In wet state, the compressive strength of the pure
alginate and the mixed CPC/alginate scaffolds decreased sharply to values
that are significantly lower than that of biphasic CPC-alginate and pure
CPC scaffolds. The modulus of CPC and biphasic CPC-alginate were higher
compared to that of alginate and mixed CPC-alginate scaffolds in the wet
state but showed no significant difference in the dry state. The most likely
explanation is the decrease of stiffness of alginate gels due to swelling in
aqueous media. Interestingly, compressive strength of biphasic CPC-algi-
nate scaffolds was still significantly higher than that of pure CPC scaffolds
in the wet state indicating the beneficial effect of the combination of both
phases. Figure 4.12c,d show that the stress of pure alginate and mixed CPC-
alginate scaffolds increased with compressive deformation and the scaf-
folds still held the bulk morphology without collapsing. Stress of pure CPC
scaffold increased sharply with compression at the beginning and then fell
quickly to zero after reaching the maximum value as the scaffold completely
disintegrated (Figure 4.12c,d). In contrast, the compressive strength of the
biphasic CPC-alginate scaffolds increased almost linearly with deformation
at the beginning and decreased a little after the maximum value. After 35%
compressive deformation was performed, the biphasic CPC-alginate scaf-
folds still maintained their macroscopic morphology instead of cracking into
powder as observed for pure CPC ones (Figure 4.12d).
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