Biomedical Engineering Reference
In-Depth Information
For application in skin, for example, films are preferred over
highly porous scaffolds, since cultured keratinocytes may infiltrate
these scaffolds, insteadof forming multiple cell layers on top.
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20.2.2
Porous Scaffolds
For tissues where ingrowth of cells is of importance, porous scaf-
foldsarepreferable(Fig.20.1b,d).Flat,porouscollagenorcollagen-
elastin scaffolds can be prepared by freezing and subsequently
lyophilizing a suspension of collagen and elastin.
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More specifi-
cally, a collagen(-elastin) suspension in diluted acetic acid can be
applied to a mold, frozen, and lyophilized, resulting in porous scaf-
folds.Theporestructureobservedafterfreeze-dryingresemblesthe
ice crystal network formed during the freezing process. By varying
thefreezingtemperature,andhencethevelocityoffreezing,thepore
size of the scaffolds can be varied to some degree.
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,
12
With faster
freezing, smaller ice crystals are formed, leading to a scaffold with a
smalleraverageporediameter.InFig.20.2,scanningelectronmicro-
graphs of scaffolds are shown which were frozen at three differ-
ent temperatures. The largest and most honeycomb-like pores were
formed when freezing at -20
◦
C.
Figure 20.2.
Scanning electron micrographs of porous collagen scaffolds
prepared by freezing and lyophilization of an acidic collagen suspension.
Pore size can be influenced by the freezing temperature. Using relatively
high freezing temperature (-20
◦
C) resulted in larger ice crystals compared
withthoseobtainedwithlowerfreezingtemperatures(-80or-196
◦
C).The
insets in (b) and (c) show lamellae with interconnecting struts. Bars are
100
μ
m;barsininsertsare20
μ
m.(FigurereproducedfromFaraj
et al.
2007
with permission).
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