Biomedical Engineering Reference
In-Depth Information
attempted.to.use.the.devices.containing.ODS.for.trapping.of.non-polar.aromatic.hydrocar-
bons,.aromatic.phenols,.and.aromatic.carboxylic.acids;.however,.this.was.unsuccessful.as.
the.compounds.diffused.deeply.into.the.PDMS.and.could.not.be.recovered..In.a.different.
approach,.Hu.et.al..created.PDMS.channels.(75.μm.wide.×.20.μm.deep).from.SU8.molds.and.
then.bonded.the.PDMS.channels.to.a.mesoporous.silica.(MPS).thin.ilm.(supported.on.a.
silicon.wafer).using.oxygen.plasma..They.then.applied.this.system.to.extract.low.molecu-
lar.weight.standard.proteins.from.a.deined.protein.mixture.(simulating.extraction.from.
a.biological.luid)..The.luid.moved.through.the.microchannel.using.pressure.driven.low..
After.rinsing,.the.proteins.that.had.entered.the.porous.silica.were.eluted.using.a.1:1.(V:V).
ratio. of. acetonitrile:. 0.1%. triluoroacetic. acid.. The. protein. fractionation. was. analyzed. by.
MALDI-TOF.MS..All.of.the.high.molecular.weight.proteins.in.the.mixture.were.success-
fully.removed,.and.no.signal.for.large.proteins.was.detected.at.high.mass.range.from.3,000.
to. 70,000.Da.. When. compared. with. the. MPS. ilm. without. the. microchannel,. similar. or.
greater.amounts.of.low.molecular.weight.proteins.were.recovered..A.control.experiment.
in.which.the.microchannel.was.applied.to.a.bare.Si.wafer.showed.no.protein.retention.
In. a. study. combining. magnetic. nanoparticles. and. microluidics,. Lee. et. al.. (2011a). dem-
onstrated.a.microluidic.continuous-low.protein.separation.process.in.which.silica-coated.
superparamagnetic.nanoparticles.interacted.preferentially.with.hemoglobin.(based.upon.elec-
trostatic.interactions).in.a.mixture.with.bovine.serum.albumin,.formed.protein-nanoparticle.
aggregates.through.electrostatic.interactions,.and.were.recovered.by.magnetophoresis..The.
microchannels. used. were. standard. PDMS. channels. (length,. 0.03.m;. width,. 100.μm;. height,.
143.μm).. In. this. study,. the. MNPs. were. synthesized. in. the. presence. of. a. stoichiometrically.
limiting.amount.of.poly(-acrylic.acid).(PAA)..This.limiting.amount.of.PAA.led.to.incomplete.
coating.of.the.nanoparticles.with.PAA,.resulting.in.nanoclusters..These.nanoclusters.were.
then.coated.with.silica..These.clusters.retained.their.superparamagnetic.properties,.but.also.
had. suficiently. strong. magnetization. to. be. recovered. from. a. lowing. stream.. In. addition,.
once.the.Hb.was.bound,.the.particles.tended.to.aggregate.as.the.result.of.two.consecutive.
processes:.rapid.adsorption.of.protein.onto.the.silica.surface,.and.subsequent.aggregation.by.
bridge. formation.. The. high. magnetization. of. the. magnetic. nanoclusters,. coupled. with. the.
dynamic.aggregation.phenomena,.allowed.them.to.operate.with.low.magnetic.ield.gradients.
(∼6.Tm
−1
).and.rapid.low.speeds.(∼10
−3
/ms).and.obtain.quantitative.recovery.of.both.proteins,.
the.Hb.bound.to.the.nanoparticles.and.the.BSA.in.the.efluent.stream.
In.a.inal.example.of.microluidics.applied.to.bioseparations,.Mu.and.coworkers.developed.
a.smart.surface.chip.in.which.the.inner.surface.of.the.chip.channel.was.irst.sputter.coated.
with. a. thin. layer. of. gold,. which. was. then. modiied. with. loosely. packed. self-assembled.
monolayers. (SAMs). of. thiols. with. terminal. carboxylic. or. amino. groups. (Mu. et. al.. 2007)..
Application.of.an.electric.potential.could.change.the.conformation.of.these.pendant.groups,.
permitting.alternation.of.the.surface.between.a.hydrophilic.and.hydrophobic.state..These.
microchips.can.thus.be.used.to.selectively.adsorb.and.release.proteins.upon.changing.the.
electrical.potential..They.applied.this.to.two.model.proteins,.avidin.and.streptavidin,.which.
were.readily.adsorbed.by.the.smart.chips.under.negative.and.positive.potential,.respectively..
More.than.90%.of.the.protein.could.be.released.upon.changing.the.electrical.potential..They.
were.also.able.to.separate.avidin.and.streptavidin.mixtures.with.1:1.and.1:1000.molar.ratios.
15.3.3 Cell and Microbial Culture
While. nanotechnology. has. been. applied. extensively. in. a. wide. variety. of. cell-culture.
activities. including. tissue. engineering,. drug. delivery,. and. biosensors. (Lee. et. al.. 2008a;.
Cheng. and. Kisaalita. 2010;. Cui. et. al.. 2010),. the. focus. of. this. section. will. be. on. the. use. of.
