Biomedical Engineering Reference
In-Depth Information
2.13 BimodalMolecularImagingProbes
Dual-.or.multimodality.molecular.imaging.is.the.synergistic.combination.of.two.or.more.
detection.techniques.in.order.to.compensate.for.the.inadequacy.of.each.imaging.modal-
ity.alone..A.major.advantage.is.that.it.can.provide.complementary.information.with.more.
accuracy.and.reliability.
146
.For.instance,.the.high.sensitivity.of.optical.luorescence.imag-
ing.permits.the.obtaining.of.detailed.information.at.subcellular.levels,.although.it.has.lim-
ited.deep.tissue.penetration,.and.lack.of.quantiication,.anatomic.resolution,.and.spatial.
information..MRI,.on.the.other.hand,.is.more.suited.for.following.the.in.vivo.distribution.
of.molecules.and.providing.anatomical.reference.points..However,.it.has.impartially.low.
contrast.agent.sensitivity.
26
.Accordingly,.there.is.considerable.interest.in.developing.dual-
modality.contrast.agents.for.combined.optical.and.MR.imaging,.due.to.their.exceptional.
tissue.contrast.and.spatial.resolution,.as.well.as.their.probable.potential.in.clinical.utility.
147
.
As.dual-mode.tumor-targeted.agents,.MRI.could.be.employed.for.lesion.localization,.while.
optical.methods.could.guide.tumor.border.identiication.during.subsequent.surgical.resec-
tion..Another.application.would.be.targeting.atherosclerotic.plaques.in.which.MRI.could.
be. utilized. for. in. vivo. plaque. identiication,. whereas. optical. emission. would. be. used. to.
guide.endoscopic.interventions.at.identiied.locations..Such.bimodal.imaging.techniques.
hold.great.promise.for.improving.diagnosis.and.therapy.of.several.diseases.
148
A. series. of. core-shell. CdSe-Zn1-xMnxS. nanoparticles. with. high. quantum. yield. and.
relaxivity.have.been.synthesized.for.use.in.dual-mode.optical.and.MRI.techniques..The.
amount.of.Mn
2+
.that.can.be.doped.into.the.shell.varies.with.the.thickness.of.the.shell.or.
the.amount.of.Mn
2+
.introduced.to.the.reaction..The.quantum.yield.and.Mn
2+
.concentration.
in.these.nanoparticles.were.adequate.to.produce.contrast.for.both.modalities.at.a.relatively.
low.concentration.
148
.Bifunctional.silica-coated.magnetic.QDs.consisting.of.Fe
2
O
3
.and.CdSe.
have.been.synthesized.with.superparamagnetism.and.an.eficient.quantum.yield.over.a.
broad. range. of. colors. without. the. need. for. ZnS. capping.. Different. cellular. membranes.
have.been.targeted.by.these.synthesized.nanocomposites.for.biolabeling.and.imaging.of.
living. cells.
149
. MRI. detectable. and. targeted. QDs. have. been. developed. by. paramagneti-
cally.coated.CdSe-ZnS.and.conjugated.with.cyclic.RGD.peptides.to.target.cultured.human.
endothelial. cells.. The. bimodal. character,. high. relaxivity,. and. speciicity. of. these. nano-
particles. make. them. desired. contrast. agents. for. the. detection. of. tumor. angiogenesis.
150
.
For.exploring.the.adequacy.of.dual-modality.nanoparticles.to.be.used.for.in.vivo.medical.
imaging,.paramagnetic.gadolinium.chelates.have.been.attached.to.polymer-coated.QDs..
Preliminary.cellular.and.in.vivo.animal.studies.demonstrated.the.promising.potential.of.
these. heterostructures. for. in. vivo. tumor. imaging. in. animal. models.
151
. Bimodal. AnxA5-
QD-Gd-wedge.nanoparticles.have.been.used.to.target.phosphatidylserine.on.the.surface.
of.apoptotic.cells.in.order.to.assess.anticancer.therapy.eficacy.
152
.In.vitro.experiments.dem-
onstrate.the.competency.of.these.nanoparticles.for.both.anatomic.and.subcellular.imaging.
of.structures.in.the.vessel.wall.by.the.use.of.MRI.and.photon.laser.scanning.microscopy.
153
.
Polymer-coated.Fe
2
O
3
.cores.overcoated.by.a.CdSe-ZnS.QD.shell.and.functionalized.with.
tumor-speciic.antibodies.have.been.utilized.for.magnetic.separation.of.breast.cancer.cells.
that. were. detected. by. luorescence. imaging.
154
. Heterodimer. nanoparticles. composed. of.
CdS-FePt. have. been. synthesized. by. taking. advantage. of. lattice. mismatching. and. selec-
tive. annealing. at. relatively. low. temperatures.
155
. Spherical-shaped. nanocomposites. with.
an. iron. oxide. Fe
3
O
4
. magnetic. core. and. CdSe-ZnS. quantum. dot. shell. have. been. synthe-
sized.by.Zhang.et.al.
170
.that.have.good.magnetic.response,.photostability,.chemical.activity,.
and.water.miscibility..The.multifunctional.nanoparticles.are.well.suited.for.wide-ranging.
