Biomedical Engineering Reference
In-Depth Information
(a)
(b)
(c)
(d)
O
O
NIPAM
BisAAm
NaAc
SiCl
3
APS
TEMED
Water
Coverslip
Spacers
Hidden areas
within creases
+
+
+
+
+
+
(h)
(g)
(f )
(e)
+
+
+
+
+
+
+
23°C
+
37°C
in PBS
FIGURE 12.5
Dynamic.scaffolds.based.on.a.thermo-responsible.hydrogel..(a).First,.a.topographically.patterned.substrate.is.
prepared.and.chemically.modiied..(b),.(c).Then,.a.hydrogel.is.loaded.and.polymerized.while.spacers.at.the.side.
and.a.coverslip.on.top.deine.the.inal.thickness.of.the.hydrogel.layer..(d).After.detachment.of.the.coverslip,.the.
hydrogel.is.swelled,.thereby.forming.areas.with.creases..(e),.(f).The.displayed.surface.of.the.hydrogel.is.then.
coated,.while.the.hidden.areas.remain.uncoated..(g),.(h).Deswelling.of.the.hydrogel.at.a.higher.temperature.
enables.the.modiication.of.the.previously.hidden.areas..Adapted.with.permission.from.reference.53..Copyright.
2010.Macmillan.Publishers.Ltd:.Nature.Materials.
regenerate. the. biomolecular. patterns.. Topographic. features. on. the. underlying. substrate.
determined.the.crease.positions.and.enabled.the.creation.of.arbitrary.2D.surface.chemi-
cal.patterns.through.selective.deposition.of.biochemically.functionalized.polyelectrolytes..
This. method.could.provide.a.valuable. component.for.lab-on-a-chip.devices. as.well. as.a.
dynamic.substrate.for.cell.biology.
12.3.4 Other Systems
Various.approaches.not.categorized.in.the.above.sections.have.been.developed.to.control.
cell-substrate. and. cell-cell. interactions.. For. example,. electrostatic. interactions. have. been.
applied.for.generating.patterned.cocultures..To.do.this,.Khademhosseini.et.al..developed.a.
method.that.used.layer-by-layer.deposition.of.ionic.biomolecules.to.pattern.cellular.cocul-
tures.
14
.HA,.a.biocompatible.and.biodegradable.material,.was.patterned.on.a.substrate.by.
capillary. force. lithography,. followed. by. ibronectin. adsorption. onto. the. HA-free. region..
Then,. the. irst. cell. type. was. seeded. and. only. attached. to. the. ibronectin-coated. region..
Subsequent. ionic. adsorption. of. poly-L-lysine. to. the. negatively. charged. HA. pattern. was.
used.to.change.its.surface.from.cell.repulsive.to.cell.adhesive..Finally,.the.second.cell.type.
was.seeded.and.attached.to.the.poly-L-lysine.pattern.
Hui.and.Bhatia.developed.a.technique.for.the.dynamic.control.of.cell-cell.adhesion.that.
could.affect.cellular.phenotype.
54
.In.this.system,.a.microfabricated.silicon.substrate.consist-
ing.of.two.interlocking.parts.was.manually.manipulated.to.bring.cells.in.close.proximity.
to.each.other..The.two.parts.could.be.joined.in.discrete.conigurations,.such.that.different.
types.of.cells.are.adjacent.to.one.another.or.are.separated.by.a.micron-scale.gap..By.cul-
turing.hepatocytes.and.supportive.stromal.cells.on.these.substrates,.and.by.adjusting.the.
placement.of.the.interlocking.components,.the.effects.of.paracrine.and.juxtacrine.signals.
could.be.examined.to.derive.important.insight.into.the.nature.of.these.interactions.
Takayama. et. al.. developed. a. chemomechanical. technique. that. allows. the. reversible.
control.of.cell.adhesion.and.spreading.
55
.In.this.approach,.a.parallel.array.of.cracks.in.
which. cell-adhesive. proteins. are. selectively. adsorbed. was. fabricated. on. a. PDMS. sub-
strate..The.widths.of.the.cracks.could.be.modulated.by.adjusting.the.mechanical.strain.
