Biomedical Engineering Reference
In-Depth Information
(Chang. et. al.. 2008b,. Faklaris. et. al.. 2008).. The. application. of. FNDs. as. a. magnetic. probe.
opens.up.new.possibilities.in.spintronics,.bioimaging,.and.material.sciences.
25.4.5 Magnetic resonance imaging
Magnetic. resonance. imaging. (MRI). is. a. non-invasive. technique. which. can. obtain.
tomographic.images.of.opaque.organisms..FNDs.linked.with.magnetic.nanoparticles.can.
serve.as.an.MRI.contrast.agent.to.study.the.biodistribution.of.nanoparticles.in.animals..
Chang. et. al.. have. reported. a. method. to. prepare. magnetic. NDs. (MNDs). by. microwave.
arcing.of.ND-ferrocene.mixed.powders.in.a.focused.microwave.oven.(Chang.et.al..2008a)..
The.MNDs.are.composed.of.iron.nanoparticles.chemically.bound.onto.the.surface.of.NDs.
through.graphene.layers..The.hybrid.particle.has.a.saturation.magnetization.of.∼10.emu/g.
and.a.coercivity.ield.of.155.G..They.can.be.further.converted.into.luorescent.MNDs.by.
attaching.organic.luorescent.molecules..The.resultant.MND.particles.have.greater.water.
solubility.without.any.change.in.their.intrinsic.magnetic.property..Fluorescence.microscopy.
studies.indicate.that.these.water-soluble.MND.particles.can.be.ingested.readily.by.HeLa.
cells,.likely.via.non-receptor-mediated.endocytosis.
More.recently,.Manus.et.al..have.demonstrated.that.Gd(III)-ND.conjugates.can.work.as.
an.MRI.contrast.enhancer.(Manus.et.al..2010)..An.amine-functionalized.Gd(III).compound.
is.conjugated.with.the.-COOH.groups.on.NDs.through.amide.linkage..They.determine.
a.relaxivity.of.58.82.mM
−1
.s
−1
.for.the.Gd(III)-ND.particles.and.this.value.is.at.least.10-fold.
higher. than. that. of. commercially. available. Gd(III). contrast. agents.. MRI. studies. clearly.
reveal. that. the. Gd(III)-ND. provides. enhanced. contrast. compared. to. the. unmodiied.
species.. Furthermore,. it. is. conirmed. that. the. attachment. of. the. Gd(III)-based. contrast.
agent.to.the.ND's.surface.does.not.have.a.signiicant.effect.on.the.overall.cell.viability..This.
paves.the.road.for.in.vivo.MRI.application.of.the.Gd(III)-ND.conjugates.
25.4.6 Near-Field Optical Microscopy
Near-ield.optical.microscopy.applies.near-ield.interactions.to.achieve.a.spatial.resolution.
better.than.the.diffraction.limit.of.light.(Kuehn.et.al..2001,.Sonnefraud.et.al..2008)..The.spatial.
resolution.can,.in.principle,.diminish.down.to.the.dimension.of.the.emitter..Cuche.et.al..have.
developed.techniques.to.graft.a.single.FND.particle.at.the.apex.of.an.optical.probe.for.near-
ield.optical.microscopy.(Cuche.et.al..2009)..The.resultant.tip.can.work.as.a.point-like.scanning.
single-photon.source,.which.operates.at.room.temperature.with.excellent.photostability..The.
spatial. resolution. ranges. from. 70. to. 150.nm.. The. (N-V)
−
. center. in. ND. can. also. be. applied.
as.a.nanoscopic.light.source.for.scanning.near-ield.optical.microscopy.(Kuehn.et.al..2001)..
Additionally,.the.tip.is.applicable.to.study.Förster.resonance.energy.transfer.(FRET).between.
the.(N-V)
−
.center.and.the.second.emitter.(Cuche.et.al..2009,.Chen.et.al..2011,.Tisler.et.al..2011)..
Furthermore,.the.tip.can.investigate.in.detail.the.propagation.of.surface.plasmon.polariton.
for.quantum.plasmonics.(Koselov.et.al..2009,.Cuche.et.al..2011,.Mollet.et.al..2011).
25.5 Therapeutic Applications of NDs
25.5.1 ND as a gene Delivery Vehicle
The. main. aim. of. gene. therapy. is. to. introduce. foreign. genetic. materials. into. the. cells. to.
replace.the.gene.with.abnormal.functions.or.to.enable.some.additional.functions..There.are.
