Direct electrochemical non-enzymatic assay of glucose using

JSolidStateElectrochem(2012)16:2675–2681DOI10.1007/s10008-012-1674-y

ORIGINALPAPER

Directelectrochemicalnon-enzymaticassayofglucoseusingfunctionalizedgraphene

MalledevaruMallesha&RevanasiddappaManjunatha&GurukarShivappaSuresh&JoseSavioMelo&

S.F.D’Souza&ThimmappaVenkatarangaiahVenkatesha

Received:14October2011/Revised:19January2012/Accepted:30January2012/Publishedonline:28February2012#Springer-Verlag2012

AbstractAnon-enzymaticamperometricsensorisdevel-opedbasedonthegraphiteelectrodemodifiedwithfunction-alizedgrapheneforthedeterminationofβ,D(+)-glucose.Cyclicvoltammetryandelectrochemicalimpedancespectros-copytechniquesareusedtostudythebehavior.Atomicforcemicroscopywasusedtostudythesurfacetopographyoftheworkingelectrodebeforeandafteritsmodification.Thesen-sorenabledthedirectelectrochemicaloxidationofβ,D(+)-glucoseinalkalinemediumandrespondedlinearlytotheanalyteovertherangefrom0.5×10 3to7.5×10 3Mwithalimitofdetectionof10μM.Thesensorisfoundtoexhibitabettersensitivityof28.4μAmM 1cm 2,goodstability,andshelflife.Thesensitivityofthesensortoβ,D(+)-glucosewasnotaffectedbythecommonlyco-existinginterferingsubstancessuchasL-ascorbicacid,dopamine,uricacid,andacetaminophen.

KeywordsNon-enzymatic.β,D(+)-glucose.Functionalizedgraphene.Sensor.Modification

M.MalleshaR.ManjunathaG.S.Suresh(*)

ChemistryResearchCentre,S.S.M.R.V.DegreeCollege,Jayanagar,

Bangalore560041,India

e-mail:sureshssmrv@yahoo.co.in

J.S.Melo:S.F.D’Souza

NuclearAgricultureandBiotechnologyDivision,BhabhaAtomicResearchCentre,Mumbai400085,India

T.V.Venkatesha

DepartmentofChemistry,KuvempuUniversity,JnanaSahyadri,

Shimoga577451,India

Introduction

Anumberofindustrial,biotechnological,andespeciallybiomedicalapplicationsdemandasimple,reliable,accurate,andrapidtechniquefortheanalysisofsugars,particularlyglucose.Itwasestimatedthatin2000,2.8%oftheworldpopulationwasaffectedbydiabetesmellitus,adiseasewithhyperglycemia(i.e.,elevatedbloodglucoselevel)asthemajorsymptom.So,determinationofbloodglucoseremainsagrowingconcerneventhoughtheclinicalconditionsofthediseaseareveryclearandwellunderstood.EversinceClark[1]proposedtheinitialconceptofanenzyme-basedbiosen-sorforglucosewaybackin1962,alotofresearchhasbeendonetodevelopandfabricateabiosensorforglucose.Originallyanduntilrecently,inmostoftheglucosebiosen-sors,glucoseoxidaseisusedasthemodelenzymewhichcatalyzestheoxidationofβ,D(+)-glucoseintoglucono-δ-lactoneinthepresenceofmolecularoxygen,simultaneouslyproducinghydrogenperoxide.Thenglucoseisgenerallyquantifiedbyelectrochemicaloxidationoftheliberatedhydrogenperoxideorlesscommonlybytheelectrochemicalreductionoftheconsumedoxygen.However,theformerreactionoccursatahighpositivepotential(morethan0.6V),andatthispotential,manyendogenouselectroactivesubstancessuchasL-ascorbicacid(AA),uricacid(UA),anddopamine(DA),co-existinginbiologicalfluids,arealsooxidized,thusseverelyaffectingtheselectivityofthebiosensor.Also,thegreatestdrawbackofbiosensorsistheirinstabilityoriginatingfromtheintrinsicnatureoftheen-zyme.Theselimitationsoftheenzyme-basedbiosensorsandthegrowingneedforastable,simple,reliable,andcost-effectivesensorforglucose,particularlyinthebiomedical

2676field,haveleadtotheemergenceofanewgeneration(alsocalledthefourthgeneration)ofamperometricglucosesen-sors,knownas“non-enzymatic”or“enzyme-free”glucosesensors,thatis,notinvolvinganyenzyme.

Thepioneeringworkinthefieldofnon-enzymaticglu-cosesensorwasdonein1909byWaltherLoebwhoelectro-catalyticallyoxidizedglucoseinH2SO4ataleadanode.Inspiteofdecadesofresearchinthisfield,thepracticalappli-cationofnon-enzymaticglucosesensorswaspreventedmainlybecauseofthelackofselectivity,sluggishkineticsofglucoseoxidationatmanyofthebareelectrodes,andfoulingofelectrodesurfacebytheconstituentsofrealsamplessuchaschlorideionsandproteins.However,withtheadventofnanomaterials,therewasasuddensurgeinnon-enzymaticsystems.Variousnanomaterialssuchasmes-oporousplatinum[2],nanoporousgold[3],platinumnano-tubearrays[4],CuOnanowirearrays[5],alloyssuchasplatinum–iridiumalloy[6],platinum–leadnanoparticles[7],platinum–leadnanoarrays[8],boron-dopeddiamond[9],carbonnanotubes[10],palladiumnanoparticle–graphenenanocomposite[11],andsoforth,havebeenusedinthefabricationofnon-enzymaticglucosesensorsinordertoalleviatesomeoftheirdrawbacksasmentionedabove.Majorityofthenon-enzymaticsensorsrelyonthecurrentresponseofglucoseoxidationdirectlyattheelectrodesur-face,themechanismofwhichconsiderablydependsontheelectrodematerialused.Twomodels,namelyactivatedchemisorptionsmodel[12]andincipienthydrousoxideadatommediatormodel[13]havebeenproposedtoexplainthemechanismofelectro-oxidationofglucoseatvariouselectrodematerials.

Grapheneisdescribedas“therisingstarcarbonmaterial”intheliteratureforitisthelatestnanoformofcarbontobediscoveredandisthecurrenthottesttopicinthefieldofmaterialscience.Structurally,itisaone-atom-thicktwo-dimensionalsheetofbondedsp2carbonatomsthataredenselypackedinahoney-combcrystallattice.Itisanintriguingcarbonmaterialwithextraordinaryelectrochemi-cal,electronic,andmechanicalpropertiescomparabletoorevenbetterthanthoseofcarbonnanotubes[14].Thehighsurfaceareaishelpfulinincreasingthesurfaceloadingofenzymesandothermodifyingmolecules,whiletheexcellentconductivityandsmallbandgaparefavorableforelectronicconduction.Beingsuchauniquematerial,graphenefindsapplicationsinvariousareassuchasopto-electronicdevices[15],supercapacitors[16],gassensors[17],pHsensors[18],andchemicalsensors[19].Inthelastfewyears,nano-compositesofgraphenewithpolymers,metals,andmetaloxideshavebeenwidelyusedinthefabricationofsensorsforvariousbiomoleculeslikedopamine[20],nicotinamideadeninedinucleotide[21],andglucose[22].Therefore,gra-pheneseemstobeanotherpromisingmaterialfordevelop-ingofnon-enzymaticglucosesensor.

JSolidStateElectrochem(2012)16:2675–2681

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