Biomedical Engineering Reference
In-Depth Information
and a Gd 3+ metal-chelating moiety suitable for detection by magnetic reson-
ance imaging (MRI) [105].
Because an adequate blood supply to and within tissues is an essential
factor for successful tissue regeneration, promoting a functional microvascu-
lature is a crucial factor for biomaterials.
In 2005, Lee et al. demonstrated that short self-assembling peptides form
scaffolds that provide an angiogenic environment promoting long-term cell
survival and capillary-like network formation in three-dimensional cultures
of human microvascular endothelial cells. Data showed that, in contrast to
collagen type I, the peptide scaffold inhibited endothelial cell apoptosis in the
absence of added angiogenic factors, accompanied by enhanced gene expres-
sion of the angiogenic factor VEGF. In addition, the results suggest that the
process of capillary-like network formation and the size and spatial organiza-
tion of cell networks may be controlled through manipulation of the scaffold
properties, with a more rigid scaffold promoting extended structures with
a larger inter-structure distance, as compared with more dense structures of
smaller size observed in a more compliant scaffold. These findings indicate
that self-assembling peptide scaffolds have potential for engineering vascular-
ized tissues with control over angiogenic processes. Since these peptides can
be modified in many ways, they may be uniquely valuable in the regeneration
of vascularized tissues [106].
Emerging medical technologies for effective and lasting repair of articular
cartilage include delivery of cells or cell-seeded scaffolds to a defect site to ini-
tiate de novo tissue regeneration. Biocompatible scaffolds assist in providing
a template for cell distribution and extracellular matrix (ECM) accumulation
in a three-dimensional geometry. A major challenge in choosing an appro-
priate scaffold for cartilage repair is the identification of a material that can
simultaneously stimulate high rates of cell division and high rates of cell syn-
thesis of phenotypically specific ECM macromolecules until repair evolves
into steady-state tissue maintenance.
In 2002, we made a self-assembling peptide hydrogel scaffold for cartilage
repair and developed a method to encapsulate chondrocytes within the pep-
tide hydrogel. During 4 weeks of culture in vitro, chondrocytes seeded within
the peptide hydrogel retained their morphology and developed a cartilage-
like ECM rich in proteoglycans and type II collagen, indicative of a stable
chondrocyte phenotype. Time-dependent accumulation of this ECM was par-
alleled by increases in material stiffness, indicative of deposition of mech-
anically functional neo-tissue. Taken together, these results demonstrate the
potential of a self-assembling peptide hydrogel as a scaffold for the synthesis
and accumulation of a true cartilage-like ECM within a three-dimensional cell
culture for cartilage tissue repair.
In 2005, Lee and colleagues demonstrated that self-assembling peptides
can be injected and that the resulting nanofiber microenvironments are
readily detectable within the myocardium. Furthermore, the self-assembling
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