3D Plotting of Bioceramic Scaffolds under Physiological Conditions for Bone Tissue Engineering - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 101

(a)

(b) (c)

500 µm 500 µm 500 µm

(e)

(d) (f)

50 µm

500 µm 50 µm

FIGURE 4.11
Microscopic images of plotted biphasic CPC-alginate scaffolds: (a) Top, (b) side, and (c) bot-
tom view and (d) SEM images of the top view as well as high-magnification scanning electron
micrographs of (e) CPC and (f) alginate strands.

transferred into deionized water and incubated for 1 week with a change
of water twice per day to accomplish hardening of the CPC and to remove
the incorporated oil from the P-CPC phase. PVA in the alginate strands was
mostly dissolved during this time. The mixed CaP-alginate scaffolds were
washed three times with deionized water. Finally, the composite scaffolds
were dried at air and room temperature.
In Figure 4.10, the CAD models of both composite scaffold types and the
real objects achieved by the 3D plotting process are shown. The photographs
demonstrate that the designed biphasic CPC-alginate scaffold with P-CPC
and alginate strands plotted alternately was successfully realized.
The strands of the different layers were bond closely among one another
due to the homogeneous cross-linking of alginate and setting of CPC. The
biphasic scaffolds were further stabilized by interpenetration of the cross-
linked alginate and hardened CPC strands between the layers. Micrographs
show the regular structure and organization of CPC and alginate strands
that are alternatively weaved forming an interpenetrating structure consist-
ing of an alginate and a CPC grid with macropores, open in all directions
(Figure 4.11). High magnification SEM images revealed that the CPC strands
possessed an additional microporosity and alginate strands were dense and
smooth (Figure 4.11). Mixed CPC-alginate scaffolds with completely open
macropores were also successfully fabricated using the same design param-
eters. In this composite type of scaffold, the CPC particles were evenly dis-
tributed within the alginate strands.
As it is known that CPC sets and hardens without any dimensional change
(Fernandez et al. 1995), no significant change of size was recognized for
the pure CPC scaffolds after drying. In contrast, pure alginate and mixed