Chemistry Reference
In-Depth Information
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Figure 6.2
Scanning electron micrographs (SEM) of synthetic versus biological
molecular gels. (A) A SEM of a typical small-peptide-based molecular
gel from the authors. (B) The extracellular matrix (ECM - pink) inter-
twined with nerves and nerve bundles (yellow) and ganglion cells (blue) in
front of the retina of the eye.
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(Reproduced with permission from ref. 7 Copyright
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Photo courtesy of
University of Rochester/URnano). Scale bars represent 5 mm and 2 mm,
respectively.
The ECM is a complex intertwined mesh of fibrous proteins (such as colla-
gen) and polysaccharides (such as glycosaminoglycans) secreted by cells
(Figure 6.2B).
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It serves as a structural scaffold in tissue by providing an-
chorage to cells, regulating cellular behaviour and communication via struc-
tural and chemical signals; playing a major role in their development, function
and physiology.
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Cells receive cues (mechanical, chemical) from the ECM, whilst simul-
taneously interacting with, and constantly remodelling their environment, thus
reinforcing their phenotype. By excreting proteases, such as matrix metallo-
proteinases (MMPs), cells can degrade the matrix around them and replace it
with newly synthesised ECM proteins. This process in turn affects cellular
behaviour, such as proliferation, migration, apoptosis, and differentiation
during development, tissue remodelling, and angiogenesis.
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One major driving
force in mimicking the ECM in synthetic systems arises from (besides inherent
biocompatibility) the critical role the ECM has in influencing the spreading and
differentiation of stem cells;
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this could be applied to particular advantage in
the areas of regenerative medicine/tissue engineering and three-dimensional cell
culture.
Over the years, natural materials such as collagen, chitosan
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and other
natural polymer-based gels, have featured heavily in the development of new
biomaterials for wound healing and other tissue engineering.
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Based on the
success of these naturally based polymeric gels, numerous chemically engin-
eered polymeric gels have been designed and tailored for the similar purposes in
recent times.
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However, this chapter's focus will not be on polymeric gels as
this area has already been covered in several excellent reviews.
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The following section will aim to introduce the motivation for their util-
isation in biomedical applications.
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