Biomedical Engineering Reference
In-Depth Information
Fig. 8
Schematic illustrations of the on/off switching of F1-ATPase rotation by entanglement of
the stimuli responsive supramolecular hydrogel fibers (nanomeshes). To clearly show the compo-
nent of rotary motor, F1-ATPase is represented enlarged. The figure is reproduced with permis-
sion from Ref. [
45
]
a supramolecular hydrogel that consisted of
N
,
N
′,
N
′-tris(3-pyridyl)-trimesic
amide was formed. The nitrogen heterocyclic ring and amide groups presented
in the gel were chosen to function as the biomineralization active sites where
the growth of the biominerals could begin. The role that the supramolecular
hydrogel played was evident in their tests, as they proved that the immersion
of the hydrogel into the aqueous Na
2
CO
3
solution followed by CaCl
2
solution
led to the formation of CaCO
3
while only layered structured calcite CaCO
3
was
observed in the absence of the hydrogel-Na
2
CO
3
composite matrix. A similar
trend was also observed for the calcium phosphate-hydrogel composite, where
nanoplate-like calcium phosphate was found to have enclosed the hydrogel
scaffold surface. With the results from their study, Shi et al. have successfully
demonstrated that, while the conventional sites are carboxylate groups binding
Ca
2
+
, amide and pyridyl groups binding PO
4
3
−
can also be used as biominer-
alization active sites. Furthermore, the biodegradability of the hydrogel devel-
oped in this study suggests that it can be useful for the advancement of organic
matrices which display high affinity for mineral ions and allow for clearance
from the body. Studies have also been conducted in the area of thermally respon-
sive supramolecular hydrogels, where the changes in temperature can elicit
a phase-change response in the gels, allowing them to serve various purposes.
For example, Yamaguchi and his co-workers have constructed supramolecular
nanomeshes from glycolipids and adapted them to regulate the rotary motion
of F1-ATPase [
45
]. In the experiment, a microbead unit was attached to the
F1-ATPase and also embedded in the sol/gel (Fig.
8
). Being thermally respon-
sive, nanomeshes were formed at low temperature which trapped the micro-
bead that serves as a physical hindrance to the rotary motion and switch off the
ATPase motion. Conversely, a high temperature can destroy the nanomeshes and
switch on the ATPase motion. The advantage of such regulating system would be
beneficial in the future investigation on the use of matrices to control the micro-
biomachines that are powered by biological motors.
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