Availableonlineatwww.sciencedirect.comTalanta74(2007)206–211Directelectrochemistryandelectrocatalysisofcytochromecimmobilizedongoldnanoparticles–chitosan–carbonnanotubes-modifiedelectrodeCuiliXianga,b,YongjinZoua,b,Li-XianSuna,∗,FenXua,∗aDalianInstituteofChemicalPhysics,ChineseAcademyofSciences,Dalian116023,ChinabGraduateSchooloftheChineseAcademyofSciences,Beijing100049,ChinaReceived20April2007;receivedinrevisedform24May2007;accepted24May2007Availableonline7June2007AbstractArobustandeffectivenanohybridfilmbasedongoldnanoparticles(GNPs)/chitosan(Chit)/multi-walledcarbonnanotubes(MWNTs)waspreparedbyalayer-by-layerself-assemblytechnique.Cytochromec(Cytc)wassuccessfullyimmobilizedonthenanohybridfilmmodifiedglassycarbon(GC)electrodebycyclicvoltammetry.ThedirectelectrontransferbetweenCytcandthemodifiedelectrodewasinvestigatedindetail.Cytcshowsacoupleofquasi-reversibleandwell-definedcyclicvoltammetrypeakswithaformalpotential(E0)of−0.16V(versusAg/AgCl)inpH7.0phosphatebuffersolution(PBS).TheCytc/GNPs/Chit/MWNTsmodifiedGCelectrodegivesanimprovedelectrocatalyticactivitytowardsthe−1−2appreductionofhydrogenperoxide(H2O2).Thesensitivityis92.21␮AmMcmandthecalculatedapparentMichaelis–Mentenconstant(Km)is0.791mM,indicatingahigh-catalyticactivityofCytc.ThecatalysiscurrentsincreaselinearlytotheH2O2concentrationinawiderangeof1.5×10−6to5.1×10−4Mwithacorrelationcoefficient0.999.Thedetectionlimitis9.0×10−7M(attheratioofsignaltonoise,S/N=3).Moreover,themodifiedelectrodedisplaysrapidresponse(5s)toH2O2,andpossessesgoodstabilityandreproducibility.©2007ElsevierB.V.Allrightsreserved.Keywords:Cytochromec;Goldnanoparticles;Multi-walledcarbonnanotubes;Chitosan;Nanohybrid;Directelectrontransfer1.Introductionstrates[9,10],However,thevoltammetricresponseofCytcisquitepoorattheconventionalelectrodes,mostlikelyduetoDuringthepastfewyears,thedirectelectrontransfer(DET)proteindenaturationatthemetalelectrodesurfaceleadingtoreactionbetweenredoxproteinsandelectrodesurfacehasbeenextre