Biomedical Engineering Reference
In-Depth Information
in contrast to the behavior of conventional pure ceramic scaffolds charac-
terized by a decline of stress to zero after the maximum, the compressive
stress of plotted silicon-based scaffolds with PVA as binder still hold certain
strength after reaching the maximum. For example, the plotted β-CaSiO
3
and mesoporous Ca-Si-P scaffolds still possessed about 43% and 85% of their
maximum stress at 35% of strain, respectively. The photographs taken of the
plotted scaffolds before and after mechanical testing, respectively, show that
after 35% of compression the printed silicon-based scaffolds still retained
their integrity. Porous ceramic scaffolds fabricated by conventional methods
such as polyurethane templating are brittle and very easy to disintegrate to
powder after compression, which is the main drawback of these bioceram-
ics. However, the silicon-based scaffolds prepared by 3D plotting with PVA
as polymeric binder do not only have increased mechanical stability but also
improved toughness. As a macromolecule, PVA strongly bonds the ceramic
particles after cross-linking. After compression testing, PVA fibers binding
the particles were clearly visible in SEM images (Wu et al. 2011).
The composite pastes prepared by mixing bioceramics (such as silicon-
based ceramics) and PVA in certain mass ratio were injectable and suitable
for extrusion through a nozzle with inner diameter of 610 µm
to form 3D
structures of defined inner and outer morphology by 3D plotting. The suc-
cessful and advantageous application of the approach of 3D plotting of bio-
ceramic particles by using PVA as a polymeric binder might not be limited to
the silicon-based bioceramics described herein but also useful for fabrication
of other kinds of bioceramic scaffolds consisting of mineral phases like HA
or β-T C P.
4.5 Conclusions and Future Directions
In this chapter, bioceramic scaffolds with predefined inner and outer mor-
phology, fabricated by 3D plotting of a calcium phosphate cement (CPC) and
silicon-based ceramics, respectively, were described. The newly prepared
CPC pastes allowed extended plotting and set under physiological condi-
tions. In addition, the mechanical properties including compressive strength
and toughness of plotted CPC scaffolds were improved by simultaneous plot-
ting of concentrated alginate and CPC pastes, leading to biphasic structures.
Such biphasic scaffolds were also favorable for cell attachment as well as
able to maintain controlled protein delivery. Furthermore, another biphasic
scaffold with separate layers for bone and cartilage was designed for osteo-
chondral tissue engineering and realized by plotting a CPC-alginate mix-
ture for the bony and alginate for the chondral part. On the other hand, two
novel silicon-based ceramic scaffolds (CaSiO
3
and mesoporous bioglass) fab-
ricated by 3D plotting were also introduced. These materials with tailorable
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