3D Plotting of Bioceramic Scaffolds under Physiological Conditions for Bone Tissue Engineering - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 89

(a) (e) (f)

(d)

25°C

(b)

(c)

FIGURE 4.2
The process of CPC scaffold fabrication by 3D plotting. The P-CPC paste used for plotting was
filled in a cartridge and tested for its printability: (a) uniform CPC strands can be extruded
through a stainless steel needle. (b) A 3D porous scaffold with designed structure is fabricated
by 3D plotting; (c) after completion of plotting, the scaffold is transferred into water for setting
and hardening. (d) Afterward, the scaffold is dried at room temperature and (e) is ready for
further application. (f) Scaffolds with different pore size and morphologies can be produced.

4.2.1 Preparation of the Plotable CPC Paste and
3D Plotting of CPC Scaffolds

A prerequisite for plotting of CPC scaffolds under physiological conditions
is the development of suitable CPC pastes. Conventional powder/liquid CPC
pastes are prepared by mixing solid calcium phosphate cement precursors
with water or aqueous Na 2 HPO 4 solution resulting in an injectable paste that
sets and hardens within a few minutes. This type of CPC paste is suitable
and frequently utilized for filling of bone defects in clinical applications;
however, the fast setting reaction and hardening prevents its usage for scaf-
fold fabrication by 3D plotting since the powder/liquid CPC would block
the nozzle with time. This limitation is circumvented by the application of a
newly developed CPC paste (P-CPC; patent applied by InnoTERE, Dresden,
Germany) that can be stored as a malleable paste for months. The P-CPC
is prepared by mixing 80% of the cement precursor powder with 20% of a
carrier liquid consisting of a semisynthetic biocompatible oil (short chain
triglycerides with 8-12 C atoms) and emulsifiers (Lode et al., forthcoming).
The cement powder consists of 60% α-tricalcium phosphate (α-TCP), 26%
dicalcium phosphate anhydride (DCPA), 10% CaCO 3 , and 4% precipitated
HA (Khairoun et al. 1997). The setting reaction of the P-CPC is triggered
by contact with water or aqueous solutions such as buffer and cell culture
medium in vitro or body liquids in vivo . Due to these favorable characteris-
tics, the injectability of the P-CPC is fully maintained during the plotting