Biomedical Engineering Reference
In-Depth Information
nanotubes.(Iijima.1991),.nano-onions.(Ugarte.1992),.nanohorns.(Iijima.et.al..1999),.graphenes.
(Novoselov.et.al..2004),.and.ultra-nanocrystalline.diamonds.(Greiner.et.al..1988)..Among.
these.nanocarbon.materials.investigated,.nanodiamonds.(NDs).have.gained.increasingly.
more.attention.of.life.scientists.due.to.their.potential.and.promising.applications.in.various.
domains.of.biology.and.medicine.(Ho.2009).
Diamond.is.one.of.the.best.known.allotropes.of.carbon,.comprised.solely.of.sp
3
.bonds..
It.has.several.superlative.physical.properties.including.(1).the.hardest.material.known,.(2).
the.highest.thermal.conductivity.of.any.bulk.material,.and.(3).the.largest.refractive.index.
of. all. dielectric. materials. (Field. 1992).. These. properties,. in. combination. with. its. remark-
able. chemical. inertness,.make. it.a.prevailing.material. in.jewelry.and.industrial. applica-
tions..However,.diamond.also.possesses.other.characteristics.favorable.for.biological.use..
For.example,.the.material.is.highly.biocompatible,.non-toxic,.and.environmentally.benign.
(Dion.et.al..1993)..The.surface.of.diamond.is.amenable.to.derivatization.with.a.variety.of.
organic.functional.groups.for.subsequent.conjugation.with.bioactive.molecules.(Yang.et.al..
2002,.Hartl.et.al..2004,.Nebel.et.al..2007)..Additionally,.diamond.has.a.wide.optical.trans-
parency. range. and. often. contains. atomic. defects. or. impurities. as. color. centers. (Zaitsev.
2001)..These.centers.can.emit.bright.photoluminescence.in.the.near-infrared.window.suit-
able.for.bioimaging.(Hui.et.al..2010a)..All.these.unique.characteristics.are.preserved.even.
for.diamond.at.the.nanoscale,.suggesting.that.nanodiamond.(ND).can.provide.a.unique.
carbon-based.platform.for.versatile.biological.and.biotechnological.applications.(Holt.2007,.
Krueger.2008,.Barnard.2009,.Vaijayanthimala.and.Chang.2009a,.Xing.and.Dai.2009)..It.is.
anticipated. that. the. employment. of. NDs. as. diagnostic,. imaging,. and. therapeutic. agents.
will.lead.to.better.understanding.of.living.processes.from.cellular.to.whole.animal.levels.
In.this.chapter,.we.irst.discuss.the.color.centers.of.ND.in.Section.25.2.and.the.biocom-
patibility. of. ND. in. Section. 25.3.. Then. we. outline. the. bioimaging. applications. of. ND. in.
Section.25.4.and.the.therapeutic.applications.in.Section.25.5..The.subjects.about.the.devel-
opment.and.use.of.single.color.centers.in.diamond.for.quantum.computing.and.informa-
tion.are.beyond.the.scope.of.this.chapter.and.can.be.found.elsewhere.(Santori.et.al..2010,.
Aharonovich. et. al.. 2011b).. Also,. the. design. and. fabrication. of. ND-based. drug. delivery.
patches.or.ilms.for.therapeutic.applications.has.been.comprehensively.reviewed.by.Liu.
et.al..(2009a).and.will.not.be.discussed.
25.2 Color Centers in ND
Prevailing.commercial.NDs.can.be.roughly.classiied.into.three.groups.according.to.their.
particle.size:.diamondoids.(∼1.nm),.ultra-nanocrystalline.particles.(within.few.nanometer),.
and.nanocrystalline.particles.(tens.of.nanometer)..Diamondoids.are.a.new.class.of.com-
pounds,.consisting.of.one.up.to.ten.adamantane.cages.terminated.with.H.atoms,.typically.
sub-nanometer.in.size..They.are.discovered.in.and.extracted.from.natural.petroleum.and.
have.potential.uses.in.biomedicine.(Dahl.et.al..2003)..Nanoscale.diamond.particles,.on.the.
other. hand,. can. be. synthesized. by. a. number. of. methods. including. high-pressure-high-
temperature.(HPHT).(Field.1992),.chemical.vapor.deposition.(CVD).(Spear.and.Dismukes.
1994),. and. detonation. (Shenderova. and. Gruen. 2006). processes.. These. NDs. can. emit. vis-
ible. luorescence. from. intrinsic. defects. and. impurities. (i.e.,. color. centers). when. excited.
optically.. Alternatively,. they. can. luoresce. from. color. centers. produced. extrinsically. by.
radiation.damages.(Zaitsev.2001)..The.wavelength.of.the.emission.depends.on.the.type.of.
