Biomedical Engineering Reference
In-Depth Information
poly(3,4-ethylenedioxythiophene),. polypyrrole,. poly(3-hexylthiophene),. polythiophene,.
and.polyaniline.(Xiao.et.al..2007)..Although.detailed.studies.need.to.be.conducted.on.their.
interactions.with.cells,.their.electroactivity.offers.an.attractive.feature.for.culturing.cells.
comprising.the.electrically.active.tissues.of.the.body,.such.as.the.brain,.cardiac.tissue,.and.
skeletal.muscle.
In. the. meantime,. another. well-characterized. example. involves. TiO
2
. nanotubes.. They.
were.shown.to.endow.bioactivity.to.a.Ti.surface,.leading.to.higher.human.osteoblast.cell.
attachment.and.proliferation.in.comparison.to.that.observed.on.a.lat,.untreated.area..Signs.
of. bone. lineage. appeared. at. an. earlier. time. point. for. cells. on. the. nanotube-covered. sur-
face..Precipitate.formation.(presumably.apatite.structures).appeared.solely.on.the.aforemen-
tioned.bioactive.surface.as.well.(Das.et.al..2009)..Sole.adjustment.of.TiO
2
.nanotube.diameters.
between. 30. and. 100.nm. revealed. the. tradeoffs. between. cell. adhesion. and. differentiation..
The.smallest.diameter.had.greater.cell.density,.but.the.largest.diameter.directed.more.MSCs.
toward.an.osteogenic.fate.(Oh.et.al..2009)..A.more.recent.work.highlighted.the.importance.
of. surface. chemistry. in. dictating. cell. functionality,. with. carbon-coated. TiO
2
. nanotubes.
proving.more.favorable.to.MSCs,.while.TiO
2
.sans.coating.was.more.optimal.for.osteoblasts.
(Brammer.et.al..2011b)..A.number.of.other.works.also.delve.into.the.effects.of.TiO
2
.nanotubes.
on.cell.behavior.(Bauer.et.al..2009;.Yu.et.al..2010;.Lai.et.al..2011;.Zhao.et.al..2011).
8.4 Dynamic Presentation of Topographical Cues
A.biomimetic.ECM.should.relect.the.dynamic.nature.of.cell-topography.interactions.in.vivo..
Lam.et.al..(2008).irst.demonstrated.the.principle.of.dynamic.synthetic.topography.using.
reversible.poly(dimethylsiloxane).(PDMS).surfaces.(2008)..Reversible.wavy.microfeatures.
were.fabricated.by.subjecting.the.molds.to.plasma.oxidation.and.subsequently.applying.
compressive.stress.to.induce.surface.buckling..The.study.showed.that.C2C12.myoblast.cell.
morphology.could.be.directed.dynamically.using.surface.array.transitions..An.alternative.
approach. to. fabricating. reversible. topography. is. by. exploiting. the. unique. properties. of.
shape. memory. polymers. (SMPs).. These. materials. can. change. shape. in. a. predetermined.
way.when.exposed.to.the.appropriate.stimulus..Shape.retention.and.recovery.are.typically.
facilitated.through.a.thermally.reversible.phase.transition.and.are.closely.associated.with.
the. polymer. glass. transition. temperature. (T
g
). or. melting. temperature. (T
m
). (Lendlein.
et. al.. 2002).. Recently,. Henderson. and. co-workers. reported. the. control. of. ibroblast. cell.
alignment. and. microilament. organization. using. reversible. grooved. microstructures.
embossed. into. NOA-63,. a. polyurethane-based. thiol-ene. crosslinked. SMP. (Davis. et. al..
2011).. The. study. demonstrated. the. response. of. ibroblast. cell. morphology. to. the. phase.
transformation.in.the.SMP,.although.the.large.topographical.feature.size.(∼140.μm).probably.
limited. the. response..A. more. recent. study. demonstrated. a. iner. control. of. the. dynamic.
topographical.presentation.by.using.a.custom-synthesized.PCL.that.phase.transitions.near.
the. physiological. temperature. (37°C). (Le. et. al.. 2011).. When. hMSCs. were. cultured. on. a.
micrograting.surface,.the.cell.morphology.switched.from.elongated.to.spindle-shaped.in.
response.to.a.surface.transformation.between.a.3.×.5.μm.channel.array.and.a.planar.surface.
at.40°C.(Figure.8.7)..This.on-demand,.surface-directed.change.in.cell.morphology.offers.a.
novel.means.to.study.cell-topography.interactions.with.ine.control.over.surface.feature.
size.and.geometry.and.may.represent.a.generally.applicable.method.to.investigate.a.wide.
variety.of.topography-mediated.changes.in.cell.behavior.
