Biomedical Engineering Reference
In-Depth Information
One application of such tubes may be urethra reconstruction,
which may, for instance, be necessary in males with a congenital
anomaly,suchashypospadias, whichresultsinamal-locationofthe
urethraopening.Previously,weperformedanimalexperimentswith
flat scaffolds in onlay urethroplasties.
14
In this experiment, the col-
lagen scaffolds performed equally well to a Cook SIS 1 layer graft
without noticeable voiding dysfunction or stone formation in the
course of the experiment (up to nine months). While the urothe-
lial cells fully populated the scaffold in one month, only few smooth
muscle cells were found in the scaffold, even after nine months.
More recently, we used the new collagen tubes to regenerate a crit-
ical defect of the rabbit urethra. With a tubular scaffold, additional
suturing of flat scaffolds into a collagen tube is not necessary. This
construct is now being optimized by the addition of components
(e.g., growth factors) that specifically stimulate smooth muscle cell
proliferation.
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20.3 Scaffolds with Defined Molecular Composition
20.3.1
Purification of Scaffold Components
Complex scaffolds with a predefined composition can be pre-
pared when purified individual components are at hand. Only in
this way, one can systematically study the effect of single com-
ponents on tissue response
in vivo
.Wehavepurifiedanumber
of basic scaffold components. Insoluble type I collagen is puri-
fied from bovine Achilles tendon using extractions with diluted
acetic acid, NaCl, urea, acetone, and demineralized water.
2
Insol-
uble elastin fibers are isolated from equine ligamentum nuchae
using extractions with NaCl, organic solvents, CNBr in formic acid,
urea with diluted 2-mercaptoethanol, and a trypsin digestion.
3
,
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Purity and fibril/fiber structure is analyzed by SDS-PAGE, amino
acid analysis, transmission electron microscopy (TEM), and SEM.
The isolated collagen fibrils still possess their characteristic stri-
ated banding pattern.
6
Purified elastin fibers are intact and free of
microfibrils.
3
,
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Glycosaminoglycans (heparan sulfate from bovine
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