Biomedical Engineering Reference
In-Depth Information
(e.g.,.see.Yoon.et.al..2009)..Odorants.can.be.delivered.to.the.device.using.gas.low.and.aero-
solization.of.liquids.(e.g.,.see.Goldsmith.et.al..2011)..Characterizing.OR-based.biosensors.
using. aerosolized. compounds. will. be. important. for. “ield”. applications.. Parameters. to.
take.into.consideration.when.designing.the.delivery.method.include.optimization.of.low.
rate.and.relative.humidity.of.the.device.chamber.(gas.delivery),.which.has.been.shown.to.
inluence.sensor.function.(Goldsmith.et.al..2011).
10.5.1 Field effect Transistors
There.is.great.interest.in.using.micro-.and.nanoelectronic.devices.for.biosensor.applications.
and.these.have.been.successfully.applied.to.whole-cell.OR.sensor.studies.(Marrakchi.et.al..
2007,.Lee.et.al..2009,.Ling.et.al..2010,.Liu.et.al..2010b)..These.techniques.take.advantage.of.
changes. in. electrical. properties. after. surfaces. have. been. functionalized. with. molecules.
of. interest.. Electrochemical. impedance. spectroscopy. (EIS). has. been. used. to. test. afinity.
of.a.number.of.odorants.to.the.rat.OR-I7.protein.immobilized.onto.the.sensor.surface.in.
membrane. fractions. (Hou. et. al.. 2007,. Lisdat. and. Schäfer. 2008).. This. was. shown. to. be. a.
sensitive. detection. method. and. based. on. modeling. and. experimental. results.. Alinito.
et.al..speculate.that.EIS.is.able.to.detect.speciic.protein.conformational.changes.following.
ligand.binding.based.on.their.impedance.characteristics.(Alinito.et.al..2010).
Silicon-based. ield. effect. transistors. (FETs). in. combination. with. CNTs. provide. a.
sensitive. platform. that. enables. size. reduction. and. multiplexing. of. individual. devices..
Functionalization. of. biological. materials. on. CNT-FETs. affects. the. current-voltage.
characteristics. of. the. CNT. (Chen. et. al.. 2003).. FETs. have. been. used. in. biological.
applications.to.monitor.whole.neuron.iring,.and.information.transmitted.by.this.device.
was.comparable.to.the.current.proile.of.action.potentials.observed.by.traditional.patch-
clamp.technique.(Fromherz.et.al..1991)..FETs.are.promising.platforms.for.use.in.cell-free.
biosensor. systems. (Chen. et. al.. 2003).. In. particular,. researchers. are. moving. to. the. use. of.
nanotube/wire.FET.devices.(Besteman.et.al..2003,.Star.et.al..2003)..Lipid.bilayer.assembly.
on.CNTs.has.been.successfully.achieved.(Richard.et.al..2003,.Zhou.et.al..2007)..Recently,.
CNTs.have.been.coupled.with.membrane-bound.proteins.and.proven.particularly.effective.
in. measuring. ionotropic. currents. by. channel. proteins. (Huang. et. al.. 2010,. Noy. 2011)..
Artiicial.lipid.bilayers.have.been.assembled.around.a.poly-l-lysine-coated.single-walled.
carbon. nanotubes. (SWCNTs). and. shown. to. facilitate. effective. ionic. lux. measurements.
by.ionophores,.such.as.the.gramicidin.pore.(Huang.et.al..2010,.Noy.2011)..CNTs.have.also.
been.shown.to.effectively.sense.protein.binding.via.streptavidin.in.a.lipid.bilayer.that.was.
tethered.on.top.of.the.CNT.network.(Zhou.et.al..2007).
Based.on.these.principles,.a.number.of.groups.have.used.CNT-FET.devices.for.OR.sensor.
applications.(Kim.et.al..2009,.Yoon.et.al..2009,.Goldsmith.et.al..2011).(Table.10.1,.Figure.10.2)..
Covalent. anchoring. of.
E. coli
. expressed. human. OR2AG1. onto. carboxylated. polypyrrole.
nanotubes. was. used. in. an. interdigitated. microelectrode. array,. which. was. able. to. sense.
the. model. substrate. of. this. OR. below. 1fM,. improving. detection. from. the. same. device.
where. ORs. in. lipid. bilayers. were. directly. deposited. (Kim. et. al.. 2009,. Yoon. et. al.. 2009)..
Using.nonligand.odors.as.controls,.the.authors.were.able.to.show.high.speciicity.of.this.
device.only.toward.the.natural.ligand.amyl.butyrate.(Yoon.et.al..2009)..Capturing.tagged.
mouse.ORs.on.nanotube.devices.enabled.natural.odorant.detection.comparable.to.an.in.
vivo.cellular.detection.method.and.allowed.for.the.sensing.of.2,4-dinitrotoluene.(2,4.DNT),.
a. precursor. compound. to. trinitrotoluene. (TNT),. which. suggests. that. odorant. receptors.
on.FET.biosenor.platforms.could.be.utilized.in.explosive.sensing.(Goldsmith.et.al..2011)..
Goldsmith. et. al.. have. successfully. used. liquid. spotting. to. demonstrate. the. feasibility. of.
