Biomedical Engineering Reference
In-Depth Information
structures.that.contain.metal.ions.and.oxide.ions..The.attractions.between.these.ions.are.
strong,.requiring.a.lot.of.energy.to.break.the.bonds,.leading.to.high.melting.and.boiling.
points..These.oxides.are.also.incapable.of.conducting.electricity.in.a.solid.state.but.elec-
trolysis.is.possible.in.the.molten.state..Molten.metal.oxides.can.conduct.electricity.because.
of.the.movement.and.discharge.of.the.ions.present..Some.metal.oxides.also.have.magnetic.
properties,.which.can.make.them.useful.in.a.variety.of.ields..One.issue.associated.with.
metal.oxides.is.that.they.need.to.be.protected.with.a.polymer.or.other.materials.to.pre-
vent.them.from.oxidizing,.potentially.causing.a.loss.of.their.magnetism.(Lu.et.al..2007)..
Nanoscale.metal.oxides.are.currently.used.for.a.vast.number.of.applications.including.gas.
sensing,.solar.cells,.fuel.cells,.and.data.storage..Metal.oxides.are.also.increasingly.used.for.
the. development. of. biosensors,. as. well. as. bioinorganic. nanoscaffolds.. The. metal. oxides.
used.include.iron.oxide,.aluminum.oxide,.nickel.oxide,.and.zinc.oxide.
Iron.oxide.has.many.biological.applications..Its.properties.(high.ionic.conductivity,.high.
isoelectric. point,. and. catalytic. abilities). have. made. it. particularly. useful. for. biosensor.
applications..In.recent.work,.gold.electrodes.were.coated.with.iron.oxide.nanoparticles.to.
evaluate.hydrogen.peroxide.concentrations.(Thandavan.et.al..2011)..These.nanoparticles.
were.then.conjugated.with.catalase.enzyme.(CAT),.which.is.responsible.for.decomposing.
hydrogen.peroxide.into.water.and.oxygen..Iron.oxide.nanoparticles.were.chosen.for.this.
application.because.they.are.able.to.transfer.electrons.eficiently.when.interacting.with.
the.produced.oxygen,.and.since.the.oxygen.concentration.is.dependent.on.the.hydrogen.
peroxide.concentration,.a.quantitative.estimation.of.the.hydrogen.peroxide.concentration.
can. be. made.. Iron. oxide. nanoparticles. are. also. being. tested. for. use. as. a. magnetic.
resonance.imaging.(MRI).contrast.agents.because.of.their.magnetic.properties.(Laurent.
et.al..2008)..The.magnetic.properties.of.iron.oxide.have.also.proven.useful.for.biological.
separations.and.gene.delivery..In.a.study.by.Tong.et.al..(2001),.superparamagnetic.iron.
oxide.nanoparticles.were.synthesized.for.use.in.protein.adsorption.and.puriication..The.
nanoparticles,. in. conjunction. with. poly(vinyl. alcohol). (PVA). and. glutaraldehyde,. were.
used.to.compose.a.magnetic.afinity.support.(MAS).to.which.ligands.could.adsorb,.in.
this. case,. lysozyme.. The. MAS. was. used. for. the. puriication. of. alcohol. dehydrogenase.
from. clariied. yeast. homogenates. through. magnetic. separation.. Another. potential.
application.is.coating.iron.oxide.nanoparticles.with.different.polymers.to.deliver.small.
interfering.RNA.(siRNA).(Boyer.et.al..2009;.Zhang.et.al..2010a)..In.a.study.conducted.by.
Zhang.et.al.,.superparamagnetic.iron.oxide.nanoparticles.were.synthesized.and.coated.
with.polyethylenimine.(PEI).for.siRNA.delivery.in.3D.cell.culture..These.nanoparticles.
were.driven.to.the.cells.through.a.collagen-gel.matrix.using.a.controlled.magnetic.ield..
Using.this.approach,.the.siRNA.was.successfully.transfected.into.the.cells.grown.in.3D.
culture,.and.it.was.concluded.that.this.method.could.also.be.useful.for.therapeutic.drug.
screening.
Aluminum.oxide,.also.known.as.alumina,.has.emerged.as.another.important.inorganic.
material.in.nanobiotechnology..Alumina.has.many.desirable.properties.that.make.it.useful.
in. many. different. scientiic. disciplines. including. nanobiology.. The. fact. that. alumina. is.
insoluble. in. water. is. one. of. these. properties.. This. property. is. particularly. important. in.
biological.processes.since.nanostructures.or.membranes.created.using.this.material.will.
not.degrade.while.in.a.system.under.biological.conditions..The.creation.of.anodic.alumina.
membranes. (AAMs). is. a. common. and. useful. method. for. employing. this. material. in.
nanotechnology..AAMs.are.fabricated.by.oxidizing.aluminum.with.an.anode.in.a.solution.
that.can.be.composed.of.different.acids.(sulfuric.acid,.phosphoric.acid).(Li.et.al..2008)..This.
process. creates. uniform. and. parallel. pores. in. the. AAMs. in. which. nanostructures. can.
form..Several.techniques.have.been.employed.for.the.development.of.nanostructures.out.
