Biomedical Engineering Reference
In-Depth Information
explored,.whereby.native.virions.were.mixed.with.6.nm.gold.nanoclusters..It.was.observed.
that. citrate-coated. gold. nanoparticles. would. only. interact. at. the. termini. of. the. capsids,.
leading.researchers.to.suspect.that.particles.interacted.with.the.RNA.inside.the.channel..
The.terminal.nanoclusters.could.be.enlarged.by.electroless.deposition.of.gold,.to.produce.
virus.“dumbbells”.(Balci.et.al..2007).
Material.templating.using.native.TMV.is.possible;.however,.to.afford.improved.control.
of. metal. nucleation. on. the. TMV. capsid. structure,. genetically. modiied. TMV. constructs.
offer. expanded. options.. In. 2005,. Lee. et. al.. engineered. two. cysteine. residues. onto. the.
N-terminus. of. the. capsid. protein,. which. were. uniformly. displayed. on. the. exterior. of.
the. TMV. capsid.. The. use. of. this. TMV. mutant. resulted. in. denser. nanoclusters. of. gold,.
palladium,. and. silver. than. previous. efforts. (Lee. et. al.. 2005).. The. surface-exposed. thiols.
presented. by. the. engineered. cysteine. residues. could. also. act. as. nucleation. points. for.
platinum.nanoclusters.(Lee.et.al..2006)..Other.genetic.modiications.to.TMV.can.generate.
mutants.with.capsid.structures.up.to.1000.nm.in.length—much.longer.than.the.genomic.
RNA.contained.within..These.mutants.have.been.used.to.demonstrate.nucleation.of.silicon.
dioxide.at.basic.pH,.contrasting.the.earlier. siliication.work.by.Shenton,.which. required.
strong.acidic.conditions.(Royston.et.al..2006).
One. challenge. associated. with. the. use. of. protein-based. macromolecules. in.
nanobiotechnology. is. the. incompatibility. of. these. structures. with. organic. solvents..
Immersing.a.highly.organized.hydrophilic.structure,.such.as.a.virus.capsid.in.an.organic.
solvent. can. alter. the. protein's. conformation. and. result. in. a. destabilized. capsid. or. even.
complete. denaturation.. This. can. be. a. roadblock. in. the. nanoengineering. of. viruses. as. it.
limits.the.“toolset”.one.can.use.to.modify.them..However,.it.has.been.shown.that.TMV.
can.be.made.compatible.with.nonpolar.organic.solvents.by.pegylating.the.capsid.exterior..
Modiication.of.a.native.tyrosine.(Y139).on.the.capsid.exterior.with.a.diazonium.salt.allows.
the.insertion.of.a.ketone..This.ketone.exhibits.high.reactive.selectivity.toward.PEG.chains.
modiied. with. an. alkoxyamine,. and. results. in. over. 1000. PEG. chains. per. TMV. capsid..
The.pegylated.capsids.can.be.transferred.to.organic.solvents,.and.be.subjected.to.radical.
polymerization,. while. exhibiting. remarkable. stability. (Holder. et. al.. 2010).. Additionally,.
interior.modiication.of.glutamic.acid.residues.has.allowed.the.attachment.of.an.array.of.
alkoxyamines.to.the.TMV.inner.channel.(Schlick.et.al..2005)..TMV.has.also.been.used.as.
a.biotemplate.for.other.nanoscale.materials..Conducting.polymeric.nanoibers.composed.
of.both.polyaniline.(PANi).and.polypyrrole.(PPy).have.been.deposited.on.the.exterior.of.
native.TMV.capsids.(Niu.et.al..2007).
7.6.3 Nanoscale Assembly
The. ordered. nanoscale. arrangement. of. materials. is. another. area. in. which. researchers.
have.looked.to.nature.for.inspiration..Eficient.bottom-up.assembly.offers.challenges. to.
traditional.material.design.and.processing..Case.in.point,.researchers.have.demonstrated.
assembly. of. TMV. into. ordered. ilms. on. silicon. substrates. surface. modiied. with. amine,.
methyl,. acryloxy,. or. with. a. native. oxide. (Wargacki. et. al.. 2008).. In. parallel. with. material.
synthesis,.TMV.has.been.incorporated.into.both.bottom-up.and.top-down.nanofabrication.
approaches.. One. group. has. fabricated. functionalized. three-dimensional. structures. by.
incorporating. uncoated. and. nickel-coated. TMV. into. a. photolithographic. liftoff. process..
The.nickel-coated.TMV.structures.were.then.coated.with.a.nanoscale.ilm.of.alumina.by.
atomic.layer.deposition.(ALD).(Gerasopoulos.et.al..2010)..Another.approach.for.bottom-
up. assembly. of. virus-based. nanoscale. templates. involves. the. use. of. polymer-blend.
lithography..In.brief,.silicon.wafers.are.patterned.with.a.DNA-linker.molecule.that.acts.as.
