Biomedical Engineering Reference
In-Depth Information
Microelectrode
(a)
(b)
Scan
(c)
(d)
100 µm
FIGURE 12.4
Microelectrode.patterning.of.a.surface.for.directing.cell.migration.in.(a)-(d)..The.microelectrode.can.be.used.to.
desorb.the.antibiofouling.layer,.irst.allowing.cells.to.attach.and.then.allowing.cells.to.migrate.from.the.initial.
pattern..Adapted.with.permission.from.reference.39..Copyright.2004.American.Chemical.Society.
initially.covered.with.albumin.molecules.to.prevent.cell.adhesion..When.light.was.irradi-
ated.to.cleave.the.terminal.group.of.the.SAMs,.albumin.desorbed.from.the.surface,.allow-
ing.ibronectin.deposition.and.subsequent.cell.attachment.corresponding.to.the.irradiated.
pattern..They.used.this.method.to.fabricate.an.array.composed.of.different.cell.types.and.
to. induce. cell. migration.. In. another. example,. poly(N-isopropylacrylamide). (PIPAAm).
modiied. with. a. photochromic. spiropyran. has. been. used. to. control. cell. adhesion.
48
. The.
cell.adhesiveness.of.the.polymer.surface.enhanced.by.the.UV.irradiation.was.reset.by.the.
visible.light.irradiation.and.annealing.at.37°C.
12.3.3 Temperature-Responsive Substrates
Okano. and. colleagues. utilized. a. thermo-responsive. polymer,. PIPAAm,. for. controlling.
cell-substrate.interaction.
49-52
.In.this.approach,.PIPAAm.was.covalently.grafted.as.a.thin.
layer.onto.tissue.culture-grade.polystyrene.dishes.by.electron.beam.radiation..Above.the.
lower. critical. solution. temperature. (LCST,. 32°C). of. PIPAAm,. the. polymer. network. col-
lapses,. making. the. polymer. dehydrated. and. relatively. hydrophobic,. thereby. becoming.
cell. adhesive.. Under. its. LCST. of. 32°C,. the. polymer. is. hydrated,. and. cell. attachment. is.
highly.suppressed..PIPAAm.copolymerized.with.other.monomers.can.be.designed.to.vary.
the.LCST.at.which.the.polymer.becomes.cell.adhesive..By.using.these.features,.patterned.
cocultures. were. generated. in. which. a. patterned. surface. of. PIPAAm. and. its. copolymer.
was. prepared. to. seed. two. cell. types. at. different. temperatures.. Since. the. entire. surface.
became. cell. repellent. at. lower. temperatures,. patterned. cells. could. be. removed. from. the.
temperature-responsive.surface.in.the.form.of.a.cell.sheet.
Recently,. Kim. et. al.. reported. a. dynamic. display. of. biomolecular. micropatterns. based.
on. an. elastic. creasing. instability. of. thermo-responsible. hydrogels. (Figure 12.5).
53
. In. the.
swelled. state. of. the. hydrogel. at. room. temperature,. the. hydrogel. surface. exhibited. an.
elastic. creasing. instability. that. sequesters. functionalized. regions. within. tight. folds. in.
the. surface.. When. the. hydrogel. was. deswelled. at. 37°C,. the. gel. surface. was. unfolded. to.
