Biomedical Engineering Reference
In-Depth Information
Porous collagen-based scaffolds were used in different
in vivo
animal models, including bladder,
13
urethra,
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blood vessels,
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oral
mucosa,
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,
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andseveral
in utero
reconstructions.
18
-
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20.2.2.1 Unidirectional scaffolds
When ice crystal growth is controlled, scaffolds with more defined
morphologies can be prepared using the freezing and lyophiliz-
ing technique. For instance, we can prepare scaffolds with unidi-
rectional lamellae (Fig. 20.3) using a temperature gradient which
forms between liquid nitrogen (-196
◦
C) and ambient temperature
(about 20
◦
C). Finger-shaped ice crystals will start growing from
the site of liquid nitrogen towards the site of higher temperature.
Afterlyophilization,itresultsinascaffoldwithunidirectionallamel-
larstructures.
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Theindividuallamellaeareconnectedbythinstruts
of approximately 1-2
μ
m.
The principle is equivalent to the one described by Schoof
et al
.
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Punches of these scaffolds with unidirectional lamellae have
beenusedtoguideSchwanncells
in vitro
,whichmayultimatelycon-
tribute to functional repair ofperipheral nerve lesions.
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,
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20.2.3
Tubular Porous Scaffolds
Tubular scaffolds are the materials of choice when replacing tubu-
lar structures in the body. Small-diameter tubes are necessary for
Figure 20.3.
Scaffolds with unidirectional lamellae (connected by thin
struts), prepared using a temperature gradient between -196
◦
Cand
room temperature. Unidirectional scaffolds were visualized by (a) light
microscopy (toluidine blue-stained epon sections), (b) SEM, and (c) micro-
computedtomographyafterheavymetalstaining.Barsare100
μ
m.(Figure
reproduced from Faraj
et al.
2009 with permission).
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