Biomedical Engineering Reference
In-Depth Information
dyes.(indocyanine.green),.they.can.be.employed.for.selective.photothermal.treatment.of.
cancer..Speciic.cell.targeting.functions.can.be.embedded.by.the.incorporation.of.targeting.
molecules,. and. the. SPR. absorption. and. scattering. of. the. nanoparticles. can. be. exploited.
for.a.dual-function.imaging/therapy.approach..El-Sayed.et.al..demonstrated.this.effect.
by.employing.high-scattering.gold.nanoparticles.(40.nm).for.the.photothermal.destruc-
tion.of.oral.squamous.carcinoma.cell.lines,.by.incorporating.anti-EGFR.antibody.on.the.
nanoparticles.and.laser-irradiating.(continuous-wave.(CW)).labeled.cells.
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.Trypan.blue.
cell.assays.showed.that.the.cancerous.cells.were.compromised,.whereas.the.healthy.cells.
were.intact..Laser.energy.thresholds.for.total.cell.annihilation.are.also.reached.at.much.
lower.strengths.for.diseased.cells.than.for.healthy.normal.cells.
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.The.need.for.deeper-
tissue. in. vivo. photothermal. strategies. requires. light. energy. at. the. near-infrared. (NIR).
region,. compared. with. visible. light. for. in. vitro. and. skin. and. surface. cancer. applica-
tions..This.region.presents.the.highest.transmittivity.for.hemoglobin.and.water.(promi-
nent.tissue.components),.with.NIR.light.penetration.possible.for.up.to.a.few.centimeters.
depth.
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. The. use. of. gold. nanoparticles. for. NIR. imaging. and. photothermal. therapy. of.
cancer. can. be. achieved. by. changing. the. optical. properties. of. the.Au. nanoparticles. by.
changing.their.shape.
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24.4.3 Antiangiogenic Gold Nanoparticles
Angiogenesis. as. a. regulatory. process. for. structural. and. functional. integrity. of. organ-
isms.plays.an.important.role.in.the.maintenance.of.function.and.structure..There.are.two.
types.of.angiogenesis..The.irst.is.the.normal.angiogensis.that.is.responsible.for.positive.
developments,. such. as. the. growth. of. a. fetus. to. an. adult,. and. thus. the. maintenance. of.
the.organism..The.second.type,.abnormal.angiogenesis,.is.known.to.be.the.driving.force.
behind.the.formation.and.proliferation.of.many.melanomas.and.cancers,.which.employ.
the.angiogenesis.process.to.advance.their.supply.of.blood,.leading.to.tumor.growth.and.
proliferation..Gold.nanoparticles.have.been.shown.to.inhibit.angiogenesis.by.inhibiting.
the.VEGF165-induced.proliferation.in.HUVEC.cells.
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.On.top.of.this,.gold.nanoparticles.
were.shown.to.be.nontoxic.compared.with.untreated.cells..Various.cell.lines.also.showed.
similar.proiles,.with.the.presence.of.the.heparin-binding.domain.on.the.VEGF165.shown.
as.a.requisite.factor.in.the.inhibition.by.gold.nanoparticles..This.observation.allows.for.
the. application. of. gold. nanoparticles. as. possible. therapies. for. many. cancer. types. and.
carcinomas.
24.5 FateofNanoparticlesinLiveSystems
The.use.of.modiied.nanoparticles.for.drug.delivery.systems.maximizes.the.localization.
of.the.delivery.agents.and.their.subsequent.accumulation.only.at.the.target.site.
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.The.EPR.
effect.(for.passive.targeting).and.surface.derivatization.(for.active.targeting).are.important.
in.the.speciicity.of.the.delivery.systems.
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.Nanoparticle-based.delivery.systems.are.a.good.
method.for.the.circumvention.of.adverse.effects.due.to.the.migration.of.the.nanoparticles.
to.other.sensitive.parts.of.the.body.
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.The.exact.mechanism.and.pathways.of.how.the.body.
rids.itself.of.nanoparticles.are.still.the.subject.of.intense.investigation,.with.the.liver.most.
likely. the. destination. of. the. spent. nanoparticles,. with. their. design. such. that. they. pass.
freely.in.other.organs.but.can.be.retained.in.the.liver.and.spleen.
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