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**Towhomcorrespondenceshouldbeaddressed.E-mail:philm@northwestern.eduPublished19October2007,Science318,426(2007)DOI:10.1126/science.1147241ThisPDFfileincludes:MaterialsandMethodsFigs.S1toS10TablesS1toS3ReferencesSupportingOnlineMaterial123456789101112131415161718192021222324Mussel-inspiredSurfaceChemistryforMultifunctionalCoatingsHaeshinLee1,SharaM.Dellatore2,WilliamM.Miller2,4,PhillipB.Messersmith1,3,4*1BiomedicalEngineering,2ChemicalandBiologicalEngineering,3MaterialsScienceandEngineering,4InstituteforBioNanotechnologyinMedicine,NorthwesternUniversity,2145SheridanRd.,Evanston,IL60208,USA.MaterialsandsubstratepreparationPlatinum,silver,copper,andpalladium(AlfaAesar,WardHill,MA),sapphire(Al2O3,RubiconTechInc.IL),quartz(MTIcrystal,MA),stainlesssteel,NiTi,Si(MEMCelectronics,Italy),Carbothane®,Tecoflex®,polycarbonateandpolyethyleneterephthalate(PET)(McMasterCarrInc,Chicago,IL),poly(styrene)(Sigma),glass(Fischerscientific),polydimethysiloxane(PDMS,Sylgard184,Dowcorning),GaAs(UniversityWafer,Boston,MA),andsiliconnitride(generousdonationbyDr.Keun-HoKimandProf.H.Espinosa,NorthwesternUniversity)werecleanedultrasonicallyin2-propanolfortenminutesbeforeuse.Titanium(20-50nm)andgold(20nmdepositedonto5nmTi)surfaceswerepreparedbyelectronbeamdeposition(EdwardsFL400,BocS1Edwards,Sussex,UK)onSi-wafers.PDMS(DowCorning)waspreparedbymixing10partsofbackboneand1partofcuringagentandcuredat10012345678910111213141516171819202122oCfor2hrs.PolydopaminecoatingDopamine(2mg/mL)wasdissolvedin10mMTris-HCl(pH8.5),andsubstratesweredippedintothesolution.pH-inducedoxidationchangesthesolutioncolortodarkbrown.Stirringand/orverticalsampleorientationwerenecessarytopreventnon-specificmicroparticledepositiononsurfaces.ThecoatedsurfaceswererinsedwithultrapurewateranddriedbyN2gasbeforestorageortreatedasdescribedbelowforad-layerformation.Surfacescoatedinthismannerremainstableoninorganicsubstratesunlessscratched,treatedbyultrasound,ordippedinastrongacidsolution(pH1).Coatingsonsomeorganicsubstratessuchaslatexbeads,Sephadexresinsandsomecommercialplastics,remainstableeveninthepresenceof1NHClcombinedwithultrasound.Incubationofdopaminesolutionatroomtemperatureforseveraldays(3days)priortoimmersionofsubstratesdidnotproducesurfacediscoloration(todark-brown)typicalofpolydopaminecoatings,indicatingthatthecoatingdidnotoccurorwastoothintoobservevisually.Furthermore,thecoatingreactionappearstobepreventedunderanaerobicconditions,sincepurgingofdopaminesolutionwithargonresultedindramaticallyreducedsolutioncolorchangeandcoatingformationonimmersedsubstrates.AnalysisofpolydopaminemolecularweightinsolutionwasperformedonaDawnEOS(WyattTechnology,SantaBarbara,CA)GPCsystemusingamobilephasebufferof50mMsodiumphosphate,100mMNaCl,pH6.5withaflowrateof0.3mL/minandShodex-OHcolumns.Thesamplewasfilteredbeforeinjection(poresize~S20.8μm).12345678910111213141516171819202122Polydopamine-assistedelectrolessmetallizationPolydopamine-coatedsubstratesweremetallizedthroughimmersionincopper(II)orsilversaltsolutions.Forelectrolesscopperplating,asolutionof50mMethylenediaminetetraaceticacid(EDTA),50mMcopper(II)chloride(CuCl2),and0.1Mboricacid(H3BO3)waspreparedinultrapurewater,andthepHwasadjustedto7.0using1NofNaOH.Thissolutioncanbestoredinarefrigeratorforfutureuse.Immediatelybeforeuse,0.1Mdimethylamine-borane(DMAB)wasaddedtothecopperplatingsolution,afterwhichpolydopamine-coatedsubstrateswereplacedinthesolutionfor2-3hrsat30°C.SurfaceswerethenwashedwithultrapurewateranddriedwithN2gas.Forelectrolesssilverdeposition,useofanexogenousreducingagentwasnotnecessary,implyingoxidationoftheunderlyingpolydopaminelayerduringmetalionreduction.Polydopamine-coatedsurfacesweredippedintoa50mMaqueoussilvernitratesolutionfor18hrs(roomtemperature).SurfaceswerethenwashedwithultrapurewateranddriedwithN2gas.PhotolithographyPhotoresist(MicropositS-1818,Shipley,Marlborough,MA)wasspin-castat4000rpmfor50secandthenbakedfor1minat95oC.Utilizingacontactmaskaligner(Q2000,QuintelCorp.SanJose,CA),thephotoresistwasexposedtoUV(345nm)lightfor6sandwassubsequentlydevelopedfor40sec(MF-CD-26,Shipley,MA).Polydopaminecoatingwasappliedtothepatternedsurfacesfor3-6hrsasdescribedabove.Finally,photoresistwasremovedbyimmersioninN-methyl-pyrollidinone(NMP)S3for5-10sec.Thecoatingthickness(Figure1)wasmeasuredbyAFMonpatternedsurfaces.12345678910111213141516171819202122Polydopamine-assistedself-assembledmonolayerformationandPEGgrafting.Foralkanethiolad-layerformation,5mMofdodecanethiol(Sigma-Aldrich,Milwaukee,WI),1-mercapto-11-undecyltri(ethyleneglycol)(OEG3-C11-SH),orOEG6-C11-SH(AsemblonInc,Redmond,WA)wasdissolvedindichloromethane(DCM)whichwaspre-equilibratedbybubblingwithHeorN2.Polydopmaine-coatedsubstratesweresubsequentlyaddedfollowedbytriethylamine(finalconcentration10mM).After5hrsormore(typicallyovernightreactionfor18hrs),thesubstrateswererinsedbyeith