Biomedical Engineering Reference
In-Depth Information
region. The gold-standard therapy since 1968
has been the autotransplantation of the great
saphenous vein, a vein that runs along the leg.
The veinal graft, however, has short-term
patency (condition of not being blocked or
obstructed) success, with 12-27% of grafts
becoming occluded the first year of transplan-
tation and half of these occlusions occurring in
the first month. Arterial grafts are preferred,
given their long-term patency, but have limited
use due to their insufficient availability, small
diameter, and small length. Moreover, syn-
thetic grafts, typically polymeric, are rarely
used because they have had limited success as
large-diameter vessels [9] .
other macromolecules such as carbohydrates.
Several research groups over the past two dec-
ades have demonstrated the benefits of using
biomimicry [1, 12] .
The ECM varies among tissue types but
normally includes fibrillar collagens and elas-
tins, with diameters ranging from 10 to sev-
eral hundreds of nanometers. This network is
covered with adhesive proteins such as
laminin and fibronectin to provide sites for
cell-adhesion molecules on the cell surface to
interact with the ECM. The ECM also includes
proteoglycans and glycoproteins—to fill the
space between the fibers, act as a compression
buffer against external stressors, and serve as
a growth factor depot.
The benefits of harnessing biomimetic design
in tissue engineering scaffolds and the mecha-
nisms of its potential therapeutic effect are
explored throughout the literature [13-17] .
Most prominently detailed is the effect that
nanoscale topography has on cellular behavior.
To create an optimized cellular microenviron-
ment conducive to the growth of tissues in
natural form, biomimetic scaffolds with con-
trollable physical, mechanical, and biological
properties are required. Several traditional
techniques of creating porous 3D structures,
including salt leaching, free-form fabrication,
and gas foaming, and fairly new techniques,
including electrospinning and self-assembly,
have been used to create biomimetic 3D scaf-
folds . Older techniques result in macro- to
micro-structured bioscaffolds, whereas later
techniques result in micro- to nano-structured
scaffolds.
The fabrication of hybrid 3D scaffolds by the
merging of micro- and nanotechnologies is a
promising alternative approach to designing 3D
biomimetic scaffolds [14, 18] . Nanofibrous scaf-
folds are effective substrates for cell cultivation
and the assembly of thin tissues on the surface.
The limitation of tissue formation only on the
surface is a result of the scaffold inhibiting
7.1.2 Utilizing 3D Scaffolds
Tissue engineering , as it is currently understood,
was conceived in the late 1980s and early 1990s
[10, 11] . Since then, tissue-engineering strategies
have expanded to include cells, genes, proteins,
or other biomolecules. The bulk of a bioscaf-
fold comprises biocompatible and bioresorbable
materials that are comparable in 3D structure
to the tissue area to be regenerated. Whereas
progress has been made in the engineering of
bioscaffolds, biomimetic scaffolds are a prom-
ising class of materials that helps to rectify
the deficiencies of the preciously cited surgical
treatments. Biomimetic scaffolds are those that
closely approximate native tissue in chemical
composition, architectural intricacies, and/or
mechanical integrity.
The improved efficacy that biomimetic scaf-
folds exhibit over traditional scaffolds is a
direct result of optimally presented physical
and biochemical stimuli. These stimuli serve to
increase cellular-matrix interaction and pro-
mote cell growth, proliferation, and subse-
quently tissue formation. The most mimicked
physiological structure is the extracellular matrix
(ECM), which is composed of a hydrated pro-
teinaceous macromolecular network along with
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