Biomedical Engineering Reference
In-Depth Information
uptake compared to alginate scaffolds, indicative of increased proliferation. Inter-
estingly, higher concentration gels (3% atelocollagen I and 1.2% alginate) had
significantly increased [
35
S] sulfate uptake compared to gels of low concentration.
However, normalized GAG content within the gels indicated that the alginate gels
had significantly more GAG than any of the atelocollagen gels (there were no
significant differences in GAG content between the atelocollagen gels). Addition-
ally, the assessment of in vitro NP tissue formation on the three atelocollagen gels
over a 4 week period indicated that the 3% atelocollagen gel contained significantly
more sGAG per milligram dry tissue weight, which may indicate that scaffolds
comprised of higher concentrations of atelocollagen are able to physically entrap
and retain more GAG.
8.2.2 Elastin-Based Scaffolds
Elastin is a biopolymer that exhibits the unique ability to deform in response to
applied load and to subsequently recoil to its original molecular orientation when
that load is removed. This molecule has been shown to be present in the NP and,
although not a major component by weight, elastin is thought to play a crucial role
in aiding in the restoration of IVD matrix deformation following bending [
16
,
106
].
Under this premise, we have developed an elastin-based hydrogel scaffold for NP
tissue engineering. We hypothesized that a hydrogel scaffold that could deform and
expel water upon compression, and recover both its original shape and water
content once unloaded, could mimic the diurnal function of the native NP. Accord-
ingly, we developed an elastin-glycosaminoglycan-collagen (EGC) hydrogel scaf-
fold (Fig.
3
) composed of soluble elastin, chondroitin-6-sulfate, hyaluronic acid,
and collagen. Scaffolds were formed via gelation of the soluble mixture at 37
C
followed by lyophilization. The EGC scaffolds were subsequently crosslinked
using a carbodiimide-based fixative to allow for glycosaminoglycan incorporation,
and treated with penta-galloyl glucose, which is a polyphenolic tannin with proven
ability to stabilize both collagen and elastin [
107
,
108
]. Scaffolds were then treated
with a mixture of enzymes to relieve some of the crosslinking, yielding a highly
deformable and resilient biomaterial. Characterization of the EGC hydrogel
Fig. 3 Image frames captured from a video of an EGC hydrogel scaffold (a) prior to, (b) during,
and (c) immediately following compression, illustrating its elastic shape-memory properties
