3D Plotting of Bioceramic Scaffolds under Physiological Conditions for Bone Tissue Engineering - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 88

In this chapter, 3D plotting of diverse bioceramic scaffolds mainly based
on calcium phosphate phases for bone tissue engineering will be introduced.
The mechanical properties and cell culture in vitro have been evaluated.
Furthermore, a polymer reinforced calcium phosphate scaffold will also be
discussed as well as its improved mechanical properties and cell behavior.
In addition, 3D plotting of silicon-based bioceramic scaffolds are presented,
including the significantly improved mechanical properties and toughness.
4.2 3D Plotting of Calcium Phosphate
Cement (CPC) Scaffolds
As introduced earlier, calcium-phosphate-based materials are the distin-
guished candidates for bone repair and regeneration because of their excel-
lent properties, such as osteoconductivity, and due to the fact that calcium
phosphates are the most important inorganic constituents of biological hard
tissues. This part describes the fabrication of calcium phosphate scaffolds
by 3D plotting using an optimized calcium phosphate cement (CPC) paste.
Plotting and postprocessing steps are conducted without any heat treat-
ment, change of pH value, or involvement of organic solvents that allows—
in contrast to other RP techniques used for production of calcium phosphate
scaffolds such as powder printing or selective laser sintering—the incorpo-
ration of pharmaceutical or biological components like antibiotics, drugs,
growth factors, or even autologous constituents (such as blood components
or living cells) during scaffold fabrication. Hence, this approach seems to
be suitable to realize individualized therapies that meet the demands of the
patients not only concerning implant geometry but also with regard to the
biological aspects.
Figure 4.2 illustrates the process of CPC scaffold fabrication by 3D plot-
ting including the postprocessing steps. A ready-to-use CPC paste (P-CPC)
is filled in a cartridge that is loaded in the plotting unit. By using compressed
air, P-CPC strands are extruded and laid down to build a CPC scaffold with
predesigned structure (Figure 4.2a,b). After plotting, the CPC scaffolds are
transferred into water or buffered aqueous solutions for setting and harden-
ing (Figure 4.2c). After drying at room temperature, the CPC scaffolds can
be sterilized by gamma irradiation prior to their application (Figure 4.2d,e).
Alternatively, the process can be completely performed under sterile condi-
tions, with a setting in a cell culture medium at 37°C and without drying in
the case of incorporation of living cells or with hardening not in an aqueous
solution but in a humidified atmosphere in case of loading with growth fac-
tors or drugs. Printed CPC scaffolds with different pore sizes and morpholo-
gies can easily be achieved (Figure 4.2f).