Biomedical Engineering Reference
In-Depth Information
2 μm
100 μm
200 nm
Figure 28.3
iFyber.chemically.modiied.cotton.textile.containing.a.surface.coating.of.50.nm.metallic.nanoparticles.
build.a.stable.nanoparticle-iber.surface.interface.that.does.not.follow.the.standard.para-
digm.of.leaching.antimicrobial.agents.from.a.solid.support.(as.with.marketed.silver-based.
dressings.or.antibiotic.loaded.nanomaterials)..As.we.have.alluded.to.earlier,.metal.agent.
leaching. is. dificult. to. control. and. often. leads. to. overloading. the. target. matrix. with. the.
agent..Such.overloading.can.contribute.to.the.overuse.and.indiscriminant.release.of.metals.
into.the.environment..To.this.end,.we.have.chemically.transformed.natural.cellulose.sub-
strates.and.deposited.a.conformal.surface.coating.of.metallic.nanoparticles.using.an.in.situ.
process.whereby.cupric.ions.are.grafted.onto.the.cellulose.iber.surface.through.chelating.
groups,. and. subsequently. reduced. to. zero-valent. metal. particles. (Cady. et. al.. 2011).. This.
approach.is.supported.by.recent.demonstrations.of.copper-based.nanomaterials.for.anti-
microbial.activity.(Esteban-Cubillo.et.al..2006,.Moya.2009,.Stanic.et.al..2010)..An.example.
of.our.metallic.nanoparticle-modiied.textile.is.shown.in.Figure.28.3.
Initial. bacterial. growth. inhibition. studies. have. shown. that. our. surface-anchored.
Cu-based. nanomaterials. are. highly. effective. against. a. wide. range. of. Gram-positive. and.
Gram-negative. bacteria.. Interestingly,. our. results. show. no. signiicant. growth. inhibition.
in.zone.of.clearing.tests,.but.highly.effective.growth.inhibition.when.bacteria.are.in.direct.
contact.with.the.nanomaterials..These.results.and.several.studies.on.copper.leaching.sug-
gest.that.the.copper.nanomaterials.remain.intact.and.do.not.signiicantly.dissolve.or.dif-
fuse.into.the.test.media.or.the.environment.
In. comparison. to. our. materials,. commercial. dressings. such. as. Acticoat
®
. (Smith. &.
Nephew.Co..Ltd.,.United.Kingdom),.which.is.touted.as.a.7.day.wound.dressing.containing.
nanocrystalline.silver,.are.prepared.using.a.vapor-phase.sputtering.process.of.silver.onto.
high-density.polyethylene.mesh..This.type.of.process.provides.little.control.over.the.silver-
polyethylene.interface,.and.thus,.silver.leaches.from.the.composite.dressing..Further,.Acticoat.
and. other. commercial. antimicrobial. silver. containing. dressings. (using. either. metallic. or.
ionic.silver).typically.compensate.for.this.rapid.loss.by.overloading.the.composite.with.silver..
We.have.focused.on.fabrication.processes.that.provide.tunable.and.robust.chemistry.at.the.
