Biomedical Engineering Reference
In-Depth Information
two.different.methods.of.gene.delivery,.i.e.,.the.viral.and.non-viral.methods..The.former.
is. most. widely. accepted. in. the. ield.. Despite. being. widely. accepted,. the. virus-mediated.
gene.delivery.has.several.disadvantages.including.lack.of.safety.(such.as.the.possibility.of.
chromosomal. insertion. and. proto-oncogene. activation),. gene. size. limitation,. and. strong.
immune.reactions.against.viral.proteins,.which.hinder.repeated.administration..Because.
of.these.disadvantages,.the.non-viral.gene.delivery.methods.have.become.attractive.alter-
natives.. Non-viral. vectors. are. relatively. easy. to. prepare,. less. immunogenic. and. onco-
genic,.and.also.do.not.limit.the.gene.size.(Jin.et.al..2009)..Among.various.nanoconstructs,.
nanoparticles.have.recently.received.increasing.attention.in.the.gene.therapy.community..
Compared. with. other. nanoparticles,. ND. has. several. unique. features. to. serve. as. a. gene.
delivery. vehicle.. It. includes. inherent. biocompatibility,. water. solubility,. scalability,. high.
surface-area-to-volume.ratio,.and.numerous.functional.groups.for.easy.functionalization.
with.a.wide.range.of.therapeutics.and.targeting.molecules.(Zhang.et.al..2009a).
Zhang.et.al..have.demonstrated.that.NDs.either.covalently.or.non-covalently.functional-
ized.with.low-molecular-weight.(LMW).polyethyleneimine-800.(PEI800).can.serve.as.efi-
cient.plasmid.DNA.delivery.vehicles.(Zhang.et.al..2009a)..More.signiicantly,.the.composite.
material,.i.e.,.ND-PEI800,.shows.low.cytotoxicity.and.its.transfection.eficiency.is.similar.
to.that.of.high-molecular-weight.(HMW).PEI.(PEI25k)..Neither.ND.nor.PEI800.possesses.
this.ideal.property.when.used.alone..The.cross-linked.ND-PEI800.binds.to.plasmid.DNA.
through.electrostatic.interactions.and.protects.the.plasmid.from.deterioration..It.exhibits.70.
times.more.transfection.eficiency.than.PEI800.alone..The.transfection.eficiency.declines.
in. the. following. order,. ND-PEI800.>.PEI800.>.ND-NH
2
.>.ND.>.naked. DNA.. The. authors.
explain.that.the.higher.transfection.eficiency.of.ND-PEI800,.compared.to.ND-NH
2
,.is.due.
to.the.proton.sponge.effect.which.helps.in.the.destabilization.and.rupture.of.endosomes.
Martin.et.al..(2010).have.studied.the.Fenton.treatment.of.detonation.NDs.and.showed.that.
these.nanoparticles.can.cross.cell.membrane.and.reach.cell.nucleus.after.functionalization..
The.Fenton.treatment.helps.in.the.removal.of.graphitic.matter.on.ND.and,.at.the.same.time,.
derivatize. the. surface. with. more. hydroxyl. groups. (-OH),. which. are. useful. for. further.
conjugation.with.various.biomolecules..The.dense.-OH.groups.on.the.Fenton-treated.NDs.
possess.weighty.advantages.over.other.nanoparticles.in.bioconjugation.as.well.as.in.water.
solubility.. With. luorescently. labeled,. Fenton-treated. NDs,. the. authors. demonstrate. that.
these.particles.can.enter.nucleus.and.act.as.a.gene.carrier.for.enhanced.green.luorescent.
proteins.(GFPs).in.HeLa.cells.with.good.biocompatibility.even.after.72.h.of.incubation..The.
demonstration.of.using.ND.as.a.gene.delivery.vehicle.opens.up.exciting.horizons.for.these.
functionalized.NDs.in.gene.therapy.
Very.recently,.Chen.et.al..have.further.demonstrated.the.use.of.ND.as.a.delivery.vehicle.
for.siRNA.(Chen.et.al..2010)..ND-PEI-siRNA.complexes.are.irst.prepared.by.coating.NDs.
with. PEI800. followed. by. incubation. with. siRNA.. The. electrostatic. interactions. between.
oppositely.charged.ND,.PEI,.and.siRNA.result.in.the.complex.formation..Knockdown.of.
GFP.at.the.ratio.of.1:3.SiRNA:ND-PEI.shows.the.next.highest.knocking.down.eficiency.
in.cells,.compared.to.the.gold.standard.transfection.reagent,.Lipofectamine..In.addition,.
signiicant.decreases.of.75.6%.and.62.2%.in.GFP.expression.are.found.with.Lipofectamine.
and. ND-PEI. as. compared. to. the. control.. ND-PEI. outperforms. Lipofectamine. when. the.
transfection. is. carried. out. in. medium. with. 10%. serum,. which. closely. resembles. in. vivo.
systems.. The. biocompatibility. of. the. ND-PEI-SiRNA. complexes. is. further. conirmed.
by.MTT.assays..By.combining.ND.and.the.LMW.PEI,.the.authors.have.successfully.con-
structed.a.vector.without.cytotoxicity.but.with.the.same.transfection.eficiency.of.HMW.
PEI..This.work.justiies.the.broad.applicability.of.ND.not.only.as.a.promising.platform.for.
DNA.delivery.but.also.as.an.effective.vector.for.RNA.delivery.
