Biomedical Engineering Reference
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Fig. 6 VEGF expression in encapsulated fibroblasts related to elastic modulus (E) of the PEGDA-
PEGMA hydrogel and PEGDA hydrogel (left) Schematic of PEGDA-PEGMA hydrogels with
varying weight percentages PEGMA (right)[ 23 ]
Fig. 7 Schematic of assembling of cell-encapsulated hydrogels in a top-down manner using the
SLA Apparatus. This process consists of a platform immersed just below the surface of a large
tank of pre-polymer solution. After the layer is photopolymerized, the platform is lowered a
specified distance to recoat the part with a new layer (left). Spatial 3D layer-by-layer cell
patterning of viable cells at distinct layers. a CAD rendering of crosshatch pattern used for layer-
by-layer spatial patterning. Each layer set was 1 mm thick (10 total layers, 100 lm each).
b fluorescence image of NIH-3T3 cells encapsulated on different layer sets stained with either cell
tracker CMFDA (green) dye or CTMR (orange) dye. c cross-sectional view of a block pattern
consisting of alternating layer sets (five total layers, 100 lm each). d quantitative analysis of
(c)
showing
layer
sets
comparable
to
the
desired
500 lm
thickness.
All
values
are
mean ± standard deviation of n = 4. The scale bars are 1 mm [ 21 ]
Alternatively, hydrogels are encapsulated with endothelial progenitor or pre-
cursor cells which are capable of developing endothelial lumen. Fibrin gels have
already been extensively used to examine endothelial sprouting in a three
dimensional environment because of their fibril structure and enzymatic suscep-
tibility which enables the fibrin gels to facilitate cellular reorganization to form
endothelial lumen [ 26 ]. However, fibrin gels are too soft to be used as an implant
for revascularization therapies. Therefore, there are several efforts to control the
properties of fibrin gels or harness the structure of fibrin gels with gel-forming
synthetic polymers. For example, fibrinogens are modified with methacrylic
groups so that they can chemically cross-link with synthetic polymers such as
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