Biomedical Engineering Reference
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(b)
(a)
100 nm
FIGURE 1.3
MBG scaffolds prepared by polyurethane templating method with (a) large pore size and (b)
well-ordered mesopore channels.
was prepared by the porogen method. Yun et al
.
(2008) applied methyl cellu-
lose as the porogen to prepare porous MBG scaffolds with large-pore size of
100 µm. The second is the polymer template method, which is widely used.
We prepared MBG scaffolds with a large pore size of 400 µm by using poly-
urethane sponge as a porous template (Zhu et al. 2008). At the same time, Li
et al. (2007) also prepared MBG scaffolds using the same method. After that,
we have developed a series of MBG scaffolds with varying composition for
drug delivery and bone tissue engineering application (Zhu, Zhang, et al.
2011; Wu, Fan, Gelinsky, et al. 2011; Wu, Fan, Zhu, et al. 2011; Wu, Miron, et
al. 2011; Zhu, Zhang, et al. 2011). The prepared scaffolds possess large pores
with the size of 300 to 500 µm and well-ordered mesopores with the pore
size of 5 nm (see Figure 1.3). The advantages of the MBG scaffolds prepared
by the polyurethane sponge template method are highly interconnective
pore structure and controllable pore size (porosity), while the disadvantage
is the low mechanical strength of the material (Wu, Zhang, et al. 2010). To
better control the pore morphology, pore size, and porosity, a 3D plotting
technique (also called direct writing or printing) has been developed to pre-
pare porous MBG scaffolds. The significant advantage of this technique is
that the architectures of the scaffolds can be concisely controlled by layer-
by-layer plotting under mild conditions (Miranda et al. 2006, 2008; Franco
et al. 2010). Yun et al. (2007) and Garcia et al. (2011) prepared hierarchical 3D
porous MBG scaffolds using a combination of double polymer template and
rapid prototyping techniques. In those studies, MBG gel was mixed with
methylcellulose and then printed and sintered at 500°C to 700°C to remove
polymer templates and obtain MBG scaffolds. The main limitation of this
method for preparing MBG scaffolds is the need of methylcellulose and the
additional sintering procedure. Although the obtained MBG scaffolds have
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