Biomedical Engineering Reference
In-Depth Information
Figure 9.5
Scanning electron micrograph of a P3HB scaffold fabricated by the
sugar template method. Scale bar 500
μ
m (Reprinted with permission from [9].
Copyright (2010) Elsevier.)
remain trapped. An alternative route has been proposed using sugar
cubes as template for creation of the interconnected 3D pore structure.
For example, P3HB-Bioglass
®
composite scaffolds have been developed
by this method recently. These scaffolds exhibit a porous structure
similar to the one shown in Figure 9.5 which corresponds to the neat
P3HB scaffold [9]. Alternative matrices based on natural polymers,
for example, starch-based polymers, have also been investigated for
biodegradable polymer-Bioglass composites.
9.4.1 Thermally Induced Phase Separation
Polyester matrix composites containing bioactive glass have been devel-
oped by the thermally induced phase separation (TIPS) method. These
scaffolds are highly porous, with anisotropic tubular morphology and
extensive pore interconnectivity (Figure 9.6) [10]. TIPS is a phase sep-
aration procedure that uses a solvent that is easy to sublime. Dioxane
can used to dissolve PLA, and phase separation is induced through
the addition of a small amount of water, producing a phase with high
polymer content and one with low polymer content. Freezing the solvent
and then subliming it out leaves a porous construct. Controlling the
freezing can be used to orient the pores. The porosity of TIPS-produced
foams, their pore morphology, mechanical properties, bioactivity and
degradation rate can be controlled by varying the polymer concentration
in solution, the volume fraction of the reinforcing phase, the quenching
temperature and the polymer and solvent used. TIPS can be considered
the processing method of choice if scaffolds with highly oriented porosity
