Biomedical Engineering Reference
In-Depth Information
their.higher.tunability..Hu.et.al.
158
.compared.the.scattering,.absorption,.and.extinction.of.
AuNPs.of.different.shapes..Engineered.so.that.their.SPR.peaks.correspond.to.a.wavelength.
of.800.nm,.gold.nanorods.with.an.aspect.ratio.of.3.3.(20.nm.diameter),.gold.nanoshells.with.
a.50.nm.core.and.3.2.shell.thickness,.and.nanocages.with.a.50.nm.inner.length.and.6.nm.
thickness.were.used..The.highest.absorption.and.scattering.were.observed.in.the.nano-
cages,. followed. by. nanorods,. and. then. by. nanoshells.. The. absorption. of. AuNPs. is. ive.
times.higher.than.that.of.free.ICG,.and.their.functionalization.enables.targeted.imaging,.
as.mentioned.before..PAI.is.also.used.to.monitor.uptake.and.excretion.of.contrast.agents.
Copland.et.al.
159
.conjugated.40.nm.gold.nanospheres.to.Herceptin
®
.(a.monoclonal.anti-
body. against. HER2). to. target. SK-BR-3. breast. cancer. cells. in. vitro,
and. PAI. images. were.
obtained..At.a.tissue.depth.of.6.cm,.low.concentrations.of.AuNPs.(10
9
.AuNPs/ml).showed.
good.sensitivity.
Eghtedari.et.al.
157
.used.PEG.gold.nanorods.of.50.nm.length.and.15.nm.diameter,.with.
SPR.tuned.at.760.nm.wavelength,.and.enhanced.PAI.images.were.obtained.needing.very.
low. concentrations. of. the. nanorods.. Nanorods. have. also. been. functionalized. with. anti-
EGFR.targeting.A431.skin.cancer.cells,
160
.with.antibodies.targeting.prostate.cancer.cells,
161
.
and.with.Herceptin.antibodies.targeting.breast.cancer.cells
162
—all.showing.enhanced.PAI.
contrast..Nanorods.of.different.aspect.ratios.have.also.been.conjugated.to.two.monoclonal.
antibodies.simultaneously.targeting.both.HER2.and.CXCR4,.enabling.the.determination.
of.oncogene.expression.levels.through.imaging.
163
3.5.3.3 Dark Field Microscopy
The.scattering.properties.of.AuNPs.can.also.be.harnessed.in.imaging.applications.and.do.
not.necessarily.require.sophisticated.instruments..AuNPs.can.be.used.in.vitro.in.dark.ield.
microscopy..Images.in.dark.ield.microscopy.are.obtained.by.capturing.the.light.scattered.
by.a.sample.using.an.objective.lens.with.the.optional.addition.of.a.dark.ield.condenser.
for. higher. quality.. The. sample. gives. a. bright. image. surrounded. by. a. dark. background..
Disadvantages.include.interference.of.external.particles,.such.as.dust,.overlapping.images,.
and.nonspeciicity,.which.present.a.challenge.for.accurate.interpretation..AuNPs.can.be.
used. as. contrast. agents. in. dark. ield. microscopy. due. to. their. SPR-enhanced. absorption.
and. large. scattering. cross. sections,. where. 80. nm. AuNPs. have. ive. orders. of. magnitude.
greater.scattering.ability.than.dyes.
25
.AuNPs.can.strongly.scatter.the.light.that.corresponds.
to. their. SPR. frequency,
164
. giving. clearer. images. that. can. be. more. easily. interpreted.. In.
addition,.functionalization.of.AuNPs.allows.for.targeted.imaging..Loo.et.al.
165
.used.gold.
nanoshells.functionalized.to.target.HER2.on.breast.carcinoma.cells..Dark.ield.microscopy.
images.of.the.targeted.cells.with.gold.nanoshells.showed.high.optical.contrast.compared.
to.control.cells..El-Sayed.et.al.
166
.used.anti-EGFR-labeled.gold.nanospheres.to.target.cancer.
cells,.leading.to.a.dark.ield.image.of.well-deined.cancer.cells,.compared.to.untargeted.
normal.cells.showing.dispersed.AuNPs.
3.6 BiodistributionandToxicity
Biodistribution.and.cytotoxicity.are.important.factors.to.consider.in.biomedical.applica-
tions.when.using.AuNPs..Reports.on.the.toxicity.of.AuNPs.have.been.somewhat.mixed,.
with.some.deeming.AuNPs.noncytotoxic,.and.others.holding.a.more.reserved.view.
