Biomedical Engineering Reference
In-Depth Information
due.to.their.higher.metabolic.rates.
33,110
.Tong.et.al.
111
.demonstrated.that.when.the.AuNPs.
are.on.the.cytoplasmic.membrane,.they.require.10.times.less.laser.energy.to.destroy.the.
cell.than.when.they.are.taken.up.by.the.cell..Thus,.they.proposed.that.cell.death.by.PTT.
was.mainly.due.to.apoptosis,.initiated.by.membrane.disruption,.followed.by.blebbing.and.
damage.to.the.cell's.actin.ilaments.
The. tunability. of. colloidal. gold. nanospheres. is. limited,. and. increasing. their. size. can.
only.slightly.shift.their.SPR.into.the.NIR.region,
81,110
.though.with.an.increase.in.size,.scat-
tering.is.favored.over.absorption.
25
.Therefore,.while.colloidal.nanospheres.can.be.used.in.
treatment.of.supericial.tumors,.nanocages,.nanorods,.and.nanoshells.are.preferred.due.to.
their.high.absorption.eficiency.and.their.SPR.ranges,.which.can.be.tuned.to.extend.to.the.
NIR.and.mid-infrared.regions.
19
.This.can.be.done.by.changing.the.aspect.ratio.of.nanorods.
(length/diameter).and.nanoshells.(core/shell).
3,19,76,95,112
.Aggregated.nanospheres.or.nano-
sphere.clusters.have.also.been.used.successfully.in.PTT,.shifting.the.maximum.absorption.
from.525.nm.to.700-1,000.nm.
110
One.of.the.irst.applications.of.AuNPs.in.PTT.was.done.in.2003.by.Hirsch.et.al.
112
.using.
gold.nanoshells.and.continuous.wave.NIR.laser.to.target.breast.carcinomas.in.mice..Huang.
et. al.
110
. targeted. human. oral. squamous. carcinoma. (HSC). cells. using. 30. nm. sized. gold.
nanospheres.conjugated.to.anti-epidermal.growth.factor.receptor.(anti-EGFR).antibodies.
via.noncovalent.interactions..EFGRs.are.overexpressed.in.many.types.of.cancers,.includ-
ing.ovarian,.breast,.and.80%.of.oral.cancer.cells..With.the.exposure.to.laser.at.800.nm.for.2.
min,.each.pulse.lasting.100.fs.and.repeated.at.a.rate.of.1.kHz,.the.active.and.selective.tar-
geting.of.the.oral.cancer.cells.using.the.anti-EGFR-conjugated.nanospheres.was.achieved.
at. 20. times. lower. laser. energy. than. that. used. in. the. absence. of. the. AuNPs.. Moreover,.
aggregation.of.the.AuNPs.further.enhanced.the.photothermal.effect..Huang.et.al.
83
.used.
gold.nanorods.of.a.3.9.aspect.ratio,.which.were.also.conjugated.to.anti-EGFR.to.target.oral.
cancer.cells.using.a.laser.wavelength.of.800.nm..Compared.to.the.normal.cells,.half.the.
laser.energy.was.required.to.damage.the.cancer.cells.
O'Neal.et.al.
76
.targeted.subcutaneous.tumors.in.mice.using.gold.nanoshells.with.a.silica.
core.coated.with.thiolated.polyethylene.glycol.(PEG-SH).via.covalent.bonding.to.increase.
the.nanoparticles'.biocompatibility.and.avoid.their.uptake.by.the.reticuloendothelial.sys-
tem. (RES).. The. diameter. of. the. silica. core. synthesized. was. 100. nm,. and. the. gold. shell.
thickness.8-10.nm,.with.peak.absorption.at.805-810.nm..The.PEG.nanoshells.were.injected.
into.the.tail.vein.of.mice,.and.6.h.was.allowed.for.the.nanoshells.to.systemically.reach.and.
accumulate.in.the.tumors.passively,.due.to.the.EPR.effect..After.exposure.to.NIR.light.at.
808.nm,.complete.regression.of.the.tumors.was.observed.
Chen.et.al.
113
.successfully.used.gold.nanocages.to.actively.target.the.breast.cancer.cell.
line.SK-BR-3,.which.overexpresses.EGFR,.by.conjugating.monoclonal.anti-HER2.antibod-
ies.to.the.nanocages..The.gold.nanocages.were.synthesized.using.a.galvanic.replacement.
reaction.between.40.nm.silver.nanocubes.and.chloroauric.acid..Controlling.the.molar.ratio.
of.the.two.gives.the.ability.to.tune.the.extinction.peak.of.the.nanocages.from.the.visible.
to.the.NIR.regions..The.nanocages.in.this.study.were.tuned.to.have.an.extinction.peak.at.
810 nm.. The. nanocages. were. then. pegylated. and. conjugated. to. the. anti-HER2. antibod-
ies,.subjected.to.laser.at.810.nm,.and.thermally.ablated.the.cells.at.an.intensity.power.of.
1.5.W/cm
2
,.showing.a.linear.increase.in.effect.with.irradiation.power.density.
3.5.1.2.1.2 Radiofrequency Ablation (RFA)
The.use.of.AuNPs.has.also.been.extended.to.work.
in. RFA.. Thermal. ablation. using. an. RF. current. (10. kHz-900. MHz). causes. agitation. of. tis-
sue.ions.drawn.toward.the.alternating.current,.leading.to.friction,.which.results.in.the.gen-
eration. of. heat.
114
. However,. like. other. thermal. therapy. technologies. currently. in. use,. RFA.
