基于微膠囊的生物傳感

基于微膠囊的光學生物傳感器

Microcapsulesasopticalbiosensors

基于微膠囊的光學生物傳感器

MicrocapsulesasIntroductionpersonalizedmedicinefaster,cheaper,andmoredetaileddiagnostics.individualsmanagetheirownhealthprovidinguser-friendlytoolsformonitoringtheircurrenthealthstatus.Onepossibletool‘‘smarttattoo’’color-changingparticlesimplantationintheskinIntroductionpersonalizedmediccolor-changingparticlesresideprimarilyinthedermisrespondtochangesininterstitialfluidcompositionmeasurableshiftsintheiropticalproperties.externalopticaldevicepasslightintotheskincollectreflectedoremittedlightperformanalysistoreportinterstitialcompositiontothepatientinacontinuousorspotfashionsmarttattoocolor-changingparticlesresidExamplesofthisconcept:fluorescentmicrospheres/capsules,hollowfibermembranesencapsulatingsensingchemistry,andpolymericslabsdopedwithfluorescentreagents.thetargetspeciesareabletofreelydiffuseintothecontainer,whilepermanentlycompartmentalizingthesensingreagentsThekeytomakingthisapproachviable：engineerimplantablematerials,sensitivity,

operationalstability,andbiocompatibilityforlong-termuseExamplesofthisconcept:TheEncapsulationwithinpolyelectrolytemultilayercapsules

Nano-engineeredmicrocapsulecarriersisaneffectivemeans

ofencapsulatingsensingreagents.Differentapproachestoentrapopticalsensingassays:varioustypesofmicrovesicles,includingliposomes,polymersomes,andpolyelectrolytemicrocapsules.Polyelectrolytemicrocapsulesareformedbydepositingalternatinglayersofchargedpolymersontosacrificialtemplatesusingthelayer-by-layer(LbL)nanoscaleselfassemblyprocess,whichisfollowedbytheremovalofthetemplateviachemicaltreatment.Encapsulationwithinpolyelecttunablecompositionofthecapsulewallsprecisecontrolovertransportpropertiesmolecularweightcutoffpermeabilityinterfacialpropertieslayer-by-layer(LbL)nanoscaleself-assemblyprocessallowsforanevenwiderassortmentofcandidatematerials.Thegoalofencapsulationistotrapthesensingreagentsbehindasemi-permeableBarrier.Thesensorchemistrymustbetrappedinsufficientquantityfortheopticalresponsetobemeasured.tunablecompositionofthecapThreeprincipalmethods:Precipitation,adsorption/absorption,diffusionThreeprincipalmethods:1.Diffusionmicrocapsulesarepreparedinadvanceloadwithassayusingsimplediffusionporoustemplatespre-loadedwiththesensingmoleculeswrapinthepolyelectrolytemultilayersRemovetemplatematrix2.adsorption/absorptionAdvantage:virtuallyanyremovabletemplatecanbeusedDisadvantages:lowloadingefficiency,requirementtousematerialsthatcanbeinducedtoalterporesize,effectsencapsulatedspeciesAdvantage:allowsuseofanypolymersamenabletotheLbLassemblymethodDisadvantages:lossofadsorbed/absorbedmoleculesduringtheLbLprocess1.DiffusionmicrocapsulesareExamples：

PLL/PGAmultilayerfilmsonmesoporoussilica(MS)spheresExamples：PLL/PGAmultilayerf3.PrecipitationcoprecipitationofsensingreagentswiththetemplateswrapinthepolyelectrolytemultilayersRemovetemplatematrixAdvantage:highloadingefficiencies,minimalconcernoverdenaturationorotherdamagetosensingreagents,entrappedmoleculesremainstablyentrappedduringtheLbLprocessDisadvantages:preparetemplateseachtimeencapsulationisperformed,

sizedistributionofcoprecipitatedparticlesischanged,largeamountsofsensingreagentsusedinthecoprecipitationprocess.3.PrecipitationcoprecipitatioBiosensorsusingPEMcapsulesExamplesofbiosensorsbasedonmicrocapsuleshavebeendemonstratedwithallofthesegeneralloadingschemes,withafocusonglucoseasamodelanalyte.Inthesecases,themicrocapsulesservetheintendedpurposeofphysicallylocalizingtheentrappedchemistry,buttheneedformicrocapsulesascarriershasnotbeenfullyjustified.Itispresumablethatalossofenzymaticactivityorconstraintofconformationalchangesmightbeobserveduponimmobilization.BecauseofdiffusionlimitationintheenzymaticreactionBiosensorsusingPEMcapsulesEExamples：

nano-engineeredglucosesensormicrocapsulesbasedonglucose/galactose-bindingproteinExamples：nano-engineeredglucDifficultchallengesInthedevelopmentofstablebiosensorsthatcanoperateoverasufficientdurationtojustifyimplantationviainjection.Therearealsosomeexpectedlimitationsregardingtherelativesizeoftargetanalytesandthereceptorstobeemployed.DifficultchallengesInthedeFurtherworkunderstandtheinteractionsbetweenthecapsulesandhostbiologytoxicity,inflammation,immuneresponse,foreignbodyresponse,particlemovementlong-termfateofimplantedmaterialsAretheystableandsufficientlyinerttoallowpermanentresidenceintissue,orwilltheyeventuallydegradeandreleasesensingreagents?Furtherworkunderstandtheint[1]MikeMcShane,DustinRitter,“Microcapsulesasopticalbiosensors”,JournalofMaterialsChemistry,20(2010)8189–8193[2]AiminYu,IanR.Gentle,GaoQing(Max)Lu,“Biocompatiblepolypeptidemicrocapsulesviatemplatingmesoporoussilica