Biomedical Engineering Reference
In-Depth Information
Figure 9.17.
Cross-linkable methacrylated HA (A) and methacrylated
hyperbranched polyglycerol, of which a fragment is depicted (B).
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results indicated that the cell viability and cell cycle progression of
exposedmesenchymal stem cell monolayers wereaffected by initia-
tors, probably due to radicals generated during UV irradiations, but
osteogeniccell differentiation was notaffected.
TocontrolthemechanicalpropertiesofHAhydrogels,patterning
ofthegelswellingwasfurtherstudiedbyemployingmethacrylyoyl-
grafted HA and triethylamine as base catalyst and exposing the HA
solution to UV light for 0.5-20 minutes at the first step and adding
up sodium hydroxide as the second step.
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Degradation of the HA
hydrogel was further controlled by grafting polylactide as a spacing
domain between the HA and the methacrylate functional group.
63
ThisHA-polylactidehydrogelwasexpectedtohavedualdegradation
sites such as the HA itself by hyaluronidase and ester linkage of HA-
lactide by hydrolysis(Fig. 9.18).
•
Enzymeandoligopeptide-based
in situ
hydrogels
An
in situ
HAhydrogelwasalsofabricatedbyutilizingcharacteristics
of both oligopeptides and enzymes to mimick micro-environment
of ECM in the body. A oligopeptide-mediated HA hydrogel was syn-
thesized by using
hexa
-histidine (His) (Fig. 9.19).
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After activation
of HA (Fig. 9.19),
N
-(5-amino-1-carboxypentyl) iminodiacetic acid
(NTA) was coupled to the activated HA side chains. To chelate Zn(II)
ions,ZnSO
4
wasaddedtotheHA-NTAsolution.
α
-helicalpeptidesof
70 amino acid residues carrying a
hexa
-His peptide at both termini
and the brain-derived neurotrophic factor (BDNF) carrying a His at
theC-terminuswerecoordinatedwiththeZn(II)ionschelatedtoHA
chains for both the cross-linking of HA and the tethering of BDNF.
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