Biomedical Engineering Reference
In-Depth Information
inlammatory.cytokines.or.affect.the.amounts.of.reactive.oxygen.and.nitrate.in.the.cells,.
illustrating.no.harm.to.cell.functionality..At.the.end.of.the.study,.Shukla.and.coworkers.
concluded.that.gold.is.a.biocompatible.material.with.a.great.future.in.many.nanobiotech-
nology.and.nanomedicine.applications,.including.cancer.therapy.and.cancer.imaging.
Other. desirable. properties. of. gold. are. eficient. surface. modiication. and. easy.
conjugation. with. biomolecules.. A. classic. example. of. gold. surface. modiication. with.
bioconjugation. is. the. use. of. a. thiol. functional. group. to. attach. a. biomolecule.. A. thiol.
is. an. organic. compound. that. contains. a. sulfhydryl. group. (R-SH. or. -C-SH).. When. a.
thiol-containing. molecule. interacts. with. a. metal,. in. this. case. gold,. a. dative. bond. (also.
known. as. a. coordinate. covalent. bond). is. formed. (Hermanson. 1996).. Although. these.
bonds. are. relatively. strong,. they. are. still. at. risk. of. displacement. by. another. thiol-
containing. molecule. or. oxidation-off. of. the. surface,. if. exposed. to. oxygen. or. aqueous.
solutions..This.technique.was.used.to.create.a.gold-patterned.silicon.surface.to.compare.
the.biocompatibility.between.functionalized.silicon.and.functionalized.gold.on.silicon,.
as.well.as.to.study.the.difference.between.cell.adhesive.properties.on.the.two.different.
substrates.for.hemocompatible.and.tissue-compatible.sensor.platforms.(Lan.et.al..2005)..
In.this.case,.a.silicon.substrate.was.patterned.with.gold..The.gold.was.then.functionalized.
using. a. carboxylic. acid-terminated. alkanethiol. to. form. a. self-assembled. monolayer.
(SAM). on. the. gold,. while. polyethylene. glycol. (PEG),. a. biocompatible. polymer,. was.
attached.to.the.silicon.surface.to.prevent.protein.and.cell.adsorption..The.carboxylic.acid.
terminus.was.further.conjugated.using.
N
-hydroxysuccinimide.(NHS).in.order.to.allow.
for.coupling.of.the.protein,.ibrinogen,.with.the.SAMs.and.then.conjugation.with.either.
mouse.ibroblasts.or.mouse.macrophages..At.the.end.of.the.study,.they.concluded.that.
their.surfaces.functionalized.with.PEG.and.gold.on.silicon.almost.completely.eliminated.
protein. adsorption. and. cell. attachment. to. the. silicon. while. directing. cell. attachment.
on. the. gold—the. desired. result.. The. silicon. modiied. with. PEG. also. reduced. protein.
adsorption.and.cell.attachment.when.compared.with.the.control.substrate.(unmodiied.
silicon),.with.no.guided.cell.attachment.
Since. gold. has. proven. to. be. useful. in. many. biological. applications,. researchers. have.
wondered. if. the. innate. properties. of. gold. (or. if. the. morphology. of. gold). play. a. role. in.
protein. adhesion.. In. order. to. perform. this. study,. gold. nanospheres. and. nanorods. were.
synthesized. and. combined. with. either. lysozyme. or. α-chymotrypsin. (ChT). to. study. the.
protein-nanoparticle.adhesion.(Gagner.et.al..2011)..The.proteins.were.incubated.with.the.
nanospheres.or.nanorods.at.saturating.conditions..They.observed.that.the.proteins.adsorb.
with.a.higher.surface.density.on.the.nanorods.than.on.the.nanospheres..Neither.protein.
exhibited.any.substantial.loss.of.activity.(<10%).when.adsorbed.onto.either.nanostructure..
At. the. end. of. the. study,. they. concluded. that. the. gold's. morphology. had. no. substantial.
effect.on.protein.structure.or.function.after.adhesion.
Thus,. the. biocompatibility. and. ease. of. manipulating. gold. allow. for. the. use. of. this.
element.in.biosensing,.drug/gene.delivery,.imaging,.and.detection.purposes.
15.2.1.2 Silicon/Silica
One.of.the.most.widely.used.materials. in.the.nanotechnology.industry. today.is.silicon..
Silicon. has. long. been. used. for. electronics. and. lithography. and. is. gaining. popularity. in.
the. biological. world.. This. element. and. its. relative,. silica. (silicon. dioxide),. are. becoming.
biomaterials.as.the.worlds.of.nanotechnology.and.biology.combine..Silicon.and.silica.are.
used. for. a. variety. of. different. biological. applications,. including. bioseparations,. cell. cul-
ture,.enzyme.stabilization,.and.biosensing.
