Biomedical Engineering Reference
In-Depth Information
possible by means of nanotechnology. An example of smart composite
biomaterials are self-assembled biomaterials with cell-instructive cues.
Self-assembly is the spontaneous formation of ordered structures which
may be utilized for spatially orienting peptides with nanoscale preci-
sion [25]. Studies demonstrate that ECM-mimetic peptide constructs
which reproduce the in vivo structure of their adhesive and modula-
tory domains on a nanoscale can greatly enhance the outcome for tissue
engineering applications,in particular, self-assembled peptides have
been utilized as biomaterials. The ECM contains within its structure
certain molecules that are recognized by cells and that promote adhe-
sion, proliferation, and differentiation. One example is the Arg-Gly-Asp
(RGD) peptide, the most common epitope sequence well known for
encouraging cell adhesion [26, 27]. Several studies have utilized self-
assembled molecules incorporating the RGD sequence and have also
nanopatterned RGD to enhance the osteogenic differentiation of cells in
vitro [25].
Not only the nanostructure but also nanospacing between the self
assembled molecules affects the cellular activity via mimicking the
nanoscale spacings and orientations of cell binding sequences within
ECM. For example: the full-length fibronectin (FN) molecule contains
both an RGD adhesion site and a Pro-His-Ser-Arg-Asn (PHSRN)
synergy site spaced approximately 3.2 nm apart from each other [28]
(Figure 6.3) [29].
6.2.3.3
The Hierarchal Nanoscale Topography of Microenvironmental
Adhesive Sites
Early scaffold design only incorporated macropores at the micron scale
to allow tissue ingrowth, blood vessel formation, and nutrient delivery
to the newly formed tissue [30-35]. Now, it is speculated that alloplastic
DNA,
Heparin
Cell
Binding
Heparin,
Syndecan
HeparinCollagen
H 2 N
COOH
FN-III 9 PHSRN
FN-III 10
SS
SS
Synergy Site
RGD-Loop
H 2 N
COOH
III-CS
FN-I
FN-II
FN-III
Alternatively
Spliced FN-III
Figure 6.3 Structure of plasma fibronectin and location of major binding sites.
Reprinted from [25].
 
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