Biomedical Engineering Reference
In-Depth Information
nanometer-sized.particles.for.scientiic.and.biological.studies..Recently,.a.microemulsion.
synthesis.method.has.been.described.to.provide.water-soluble.nanoparticles.with.precise.
control.of.size.disparity.
205
.In.this.technique,.magnetic.nanoparticles.with.a.diameter.of.
4.nm.were.prepared.by.controlled.hydrolysis.of.an.aqueous.solution.of.ferrous.and.ferric.
chloride. with. ammonium. hydroxide. in. a. microemulsion. formed. by. sodium. bis(2-ethyl-
hexyl).sulfosuccinate.as.the.surfactant.and.heptanes.as.the.continuous.phase.
In.general,.iron.oxide.nanoparticles.require.coating.to.prevent.aggregation.and.to.make.
the.nanoparticles.soluble.in.aqueous.solution.or.amenable.to.further.biochemical.manipu-
lation.. A. very. high. density. of. coating. is. often. needed. to. effectively. stabilize. iron. oxide.
nanoparticles,.and.many.polymeric.coating.materials,.such.as.dextran,.carboxymethylated.
dextran,.carboxydextran,.starch,.polyethylene.glycol.(PEG),.arabinogalactan,.organic.silox-
ane,.and.sulfonated.styrene-divinylbenzene,.have.been.used.
206
.The.type.of.speciic.coat-
ing.depends.on.the.end.application.and.is.chosen.depending.upon.its.application.
Dextran. is. the. most. commonly. used. material. for. iron. oxide. nanoparticle. coating.. It.
represents.high.colloidal.stability.under.harsh.physiological.conditions,.and.hence.it.is.a.
suitable.platform.for.further.biochemical.manipulation..Dextran-coated.iron.oxide.nano-
particles.are.prepared.by.coprecipitation.from.aqueous.solution.containing.a.ferrous.salt.
and.dextran.by.adding.an.alkaline.solution.
207
.Feridex.(Endorem).(5-6.nm.core.and.80-150.
nm.total.size.range),.Resovist
®
.(Schering).(4.2.nm.core.and.62.nm.total.size),.the.ultra-small.
superparamagnetic.iron.oxide.(USPIO).Combidex
®
.(Sinerem).(4-6.nm.core.and.20-40.total.
size. range),. monocrystalline. iron. oxide. nanoparticle. (MION),. and. its. derivative,. cross-
linked.iron.oxide.(CLIO).(2.8.nm.core.and.10-30.total.size.range).are.currently.available.
dextran-coated.iron.oxide.nanoparticles.
192
.Long.blood.half-life.and.relatively. small. size.
(Table 2.1).make.the.dextran-coated.SPIO.highly.valuable.for.in.vivo.cellular.and.molecu-
lar.MRI.
Apoferritin.protein.coating.is.another.approach.to.prevent.destabilization.and.agglomera-
tion. of. iron. oxide. nanoparticles.. Ferritin,. a. well-known. iron. storage. protein,. is. composed.
of. a. hydrated. iron. oxide. core. and. a. polypeptide. apoferritin. shell.. In. the. magnetoferritin.
TABLE 2.1
Available.Coated.Iron.Oxide.Contrast.Agents
IronOxide
CoreSize
(nm)
Magnetization
at1.5T
(emug
-1
)
Total
Size(nm)
Half-Life
inBlood
Agent
CoatingMaterial
Ferumoxides.(AM125)
5
120-150
Dextran
94
~2.h
Ferumoxtran-10.(AM1227)
6
15-30
Dextran
95
>24.h
Ferucarbotran.A.
(SHU555A)
4
65
Carboxydexran
NA
3.min
Ferumoxytol.(C7228)
~7
35
Carboxymethyl.
dextran
NA
10-14.h
Lumirem.(AMI121)
10
300
Silica
NA
<5.min
Feruglose.(NC100150)
6
15-20
Methylcellulose
86
6.h
VSOP.(C184)
4
~9
Citrate.
NA
30-60.min
Magnetoferritin
~6
Ferritin
NA
~10.min
Magnetodendrimer
7-8
20-30
Carboxy-terminated.
dendrimer
~94
Magnetoliposome.
~16
~40
Liposome
NA
MION,.CLIO
~3
10-30
Dextran
68
>10.h
