Biomedical Engineering Reference
In-Depth Information
regulating. cell. behavior,. and. decreasing. this. parameter. correlating. to. a. decline. in. focal.
adhesion. formation. (Biggs. et. al.. 2008).. While. surface. nanopattern. downsizing. may. not.
always. be. favorable,. doing. so. certainly. beneited. rat.aortic. endothelial. cells. on. titanium.
surfaces.. The. 750.nm-pitch. grooves. improved. cell. density. and. alignment. more. so. than.
with.those.of.larger.spacing;.this.was.especially.apparent.when.comparing.to.the.results.
at. the. microscale. level. (Lu. et. al.. 2008).. Perhaps. further. resolution. enhancement. of. these.
nanofeatures.could.yield.even.more.effective.results.
The. Liu. group. augmented. nanogrooved. silicon. surfaces. of. varying. widths. with.
ibronectin—an. ECM. adhesion. protein.. For. the. smallest. width. (90.nm). compared. to. the.
others,.MG-63.osteoblasts.experienced.increased.cell.spreading,.decreased.alignment,.and.
somewhat.improved.contact.guidance.(but.not.as.effectively.as.lat.surfaces)..The.authors.
speculated. that. surface. chemistry. inluenced. primary. cell-substrate. interactions,. while.
the. physical. topography. had. greater. bearing. on. the. remainder. of. cellular. events. (Tsai.
et.al..2009)..Zhu.et.al..utilized.genetically.engineered.M13.phages.functionalized.with.two.
types.of.osteogenic.peptides.to.produce.grooved.ilms..MSCs.cultured.on.these.scaffolds.
exhibited. enhanced. capacity. for. proliferation. and. differentiation. into. the. bone. lineage..
These.parameters.could.be.further.modiied.by.changing.the.number.of.phage.nanoibers.
or.by.incorporating.different.peptides.onto.the.surface.(Zhu.et.al..2011).
Not.limited.to.chemical.cues,.various.other.factors.working.in.concert.with.topography.
have.been.shown.to.inluence.cell.behavior..For.example,.the.multipotent.nature.of.bone.
marrow.MSCs.was.more.optimally.preserved.on.a.nanograted.surface.by.imposing.hypoxic.
conditions.(Zhao.et.al..2010)..The.hMSCs.cultured.on.nanogratings.tended.to.grow.in.patches.
under. normoxic. conditions,. whereas. they. readily. proliferated. into. a. uniform. conluent.
layer. in. a. 2%. oxygen. tension. culture. environment.. In. another. study,. by. incorporating.
nanopatterns.into.a.microluidic.channel,.the.authors.were.able.to.understand.the.relative.
contribution.of.shear.low.and.topography.on.MSC.shape,.adhesion,.and.orientation.(Yang.
et.al..2011)..This.gives.a.glimpse.on.how.active.(shear.low).and.passive.(nanotopography).
mechanical.cues.may.work.in.a.convergent.or.divergent.manner.to.inluence.cell.behavior..
When.the.low.direction.and.grating.axis.were.parallel.or.perpendicular.to.one.another,.
the.cell.morphology.and.alignment.were.signiicantly.different..In.vivo,.interstitial.low.
and.nanotopography.do.surround.cells.in.the.ECM,.or.on.the.bone.marrow.surface,.for.
example..A.deeper.understanding.on.how.cells.respond.to.topography.in.the.presence.of.
low. would. be. a. fertile. direction. toward. recapitulating. a. biomimetic. microenvironment.
for.tissue.engineering.and.regenerative.medicine.
8.3.4  Nanotubes
Grafting.poly(methacrylic.acid).on.carbon.nanotubes.(CNTs).resulted.in.the.direct.differ-
entiation.of.human.embryonic.stem.cells.(hESCs).into.the.neuronal.lineage..The.grafted.
scaffolds,.which.had.rougher.surfaces.than.ungrafted.ones,.also.displayed.improved.cell.
adhesion.and.protein.absorption.(Chao.et.al..2010)..In.another.study,.glass.surfaces.coated.
with. multiwalled. carbon. nanotubes. (MWNTs). experienced. greater. cell. adhesion. than.
uncoated.surfaces;.but.both.saw.a.decline.in.cell.proliferation.compared.to.conventional.
tissue. culture-treated. plastic..Additionally,. the. MWNT. substrate. seemed. to. favor. neural.
differentiation.over.endodermal.differentiation.(Holy.et.al..2011)..Over.the.years,.there.has.
been.extensive.coverage.on.cellular.responses.induced.by.CNTs.(Hu.et.al..2004;.Cui.et.al..
2005;.Yun.et.al..2009;.Liu.et.al..2010;.Behan.et.al..2011).
Although. CNTs. remain. the. most. prevalent. in. use,. there. have. been. other. nanotubes.
that. are. on. par,. if. not. superior.. Conductive. polymer. nanotubes. have. been. derived. from.
