Biomedical Engineering Reference
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Fig. 10
Mechanical properties of polymeric hydrogels based on catechol-functiomalized PEG
at different pH and comparison of a chemical and a physical hydrogel, assessed by their elastic
(
G
′) and viscous (
G
″) shear moduli.
a
Frequency-dependent loss (
G
″) and storage (
G
′) moduli of
gels at pH 5 (
green
), pH 8 (
blue
), and pH 12 (
red
) (
G
′:
circles
;
G
″:
triangles
).
b
Comparison of
physically (
red
) and chemically (
black
) crosslinked hydrogels.
c
Recovery of stiffness and cohe-
siveness after tearing by shear stress (same
color
code as in
b
). Modified from Waite et al. [
121
].
Copyright 2011 National Academy of Sciences of the United States
elastic modulus at high frequencies, as shown in Fig.
10
b. After applying high
strain to the gels, the physical hydrogel regained its elastic modulus within minutes,
whereas the chemical hydrogel was damaged irreversibly, as illustrated in Fig.
10
c;
this observation indicates the ability of the catechol-based hydrogels to self-heal.
To investigate the degradability of the hydrogel, an EDTA solution (pH 4.7)
was added, fully dissolving the gel after 1 h of exposure. Apart from the degrada-
bility of the hydrogel, it could be shown that Fe
3
+
ions do not oxidize the catechol
functionalities, which would lead to covalent crosslinking.
With this work, Waite and coworkers were able to form a hydrogel mimicking
the effect that byssal threads of mussels use to adhere on surfaces. The system is
based on modified PEG, allowing possible applications in the fields of engineering
and biomedicine.
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