In vitro corrosion and biocompatibility of binary magnesium alloys

Invitrocorrosionandbiocompatibilityofbinarymagnesiumalloys

XuenanGua,YufengZhenga,b,*,YanChengb,ShengpingZhongb,TingfeiXib

aStateKeyLaboratoryforTurbulenceandComplexSystemandDepartmentofAdvancedMaterialsandNanotechnology,CollegeofEngineering,PekingUniversity,Beijing100871,ChinabCenterforBiomedicalMaterialsandTissueEngineering,AcademyforAdvancedInterdisciplinaryStudies,PekingUniversity,Beijing100871,China

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Articlehistory:Received2September2008Accepted21October2008Availableonline9November2008

Keywords:MagnesiumalloyCorrosionInvitroCytotoxicityHemocompatibilityabstract

Asbioabsorbablematerials,magnesiumalloysareexpectedtobetotallydegradedinthebodyandtheirbiocorrosionproductsnotdeleterioustothesurroundingtissues.It’scriticalthatthealloyingelementsarecarefullyselectedinconsiderationoftheircytotoxicityandhemocompatibility.Inthepresentstudy,ninealloyingelementsAl,Ag,In,Mn,Si,Sn,Y,ZnandZrwereaddedintomagnesiumindividuallytofabricatebinaryMg–1X(wt.%)alloys.Puremagnesiumwasusedascontrol.Theirmechanicalproperties,corrosionpropertiesandinvitrobiocompatibilities(cytotoxicityandhemocompatibility)wereevaluatedbySEM,XRD,tensiletest,immersiontest,electrochemicalcorrosiontest,cellcultureandplateletadhesiontest.TheresultsshowedthattheadditionofalloyingelementscouldinfluencethestrengthandcorrosionresistanceofMg.ThecytotoxicitytestsindicatedthatMg–1Al,Mg–1SnandMg–1Znalloyextractsshowednosignificantreducedcellviabilitytofibroblasts(L-929andNIH3T3)andosteoblasts(MC3T3-E1);Mg–1AlandMg–1Znalloyextractsindicatednonegativeeffectonviabilitiesofbloodvesselrelatedcells,ECV304andVSMC.ItwasfoundthathemolysisandtheamountofadheredplateletsdecreasedafteralloyingforallMg–1Xalloysascomparedtothepuremagnesiumcontrol.Therela-tionshipbetweenthecorrosionproductsandtheinvitrobiocompatibilityhadbeendiscussedandthesuitablealloyingelementsforthebiomedicalapplicationsassociatedwithboneandbloodvesselhadbeenproposed.Ó2008ElsevierLtd.Allrightsreserved.

1.Introduction

Thereisagrowinginterestinusingcorrodiblealloysin

anumberofcriticalmedicalapplications,afterdecadesofdesigning

strategiestominimizethecorrosionofmetallicbiomaterials[1].

Degradationordecomposition,mostoftenduetocorrosionofthe

materialsinthebodyfluid,hasbeendemonstratedinmetalsand

alloysthatmayhavepotentialorthopedicandcardiovascular

applications.ExamplesarepuremetalssuchasFe[2–6],Mg[7–12],

andW[13,14],andalloyssuchasFe–Mn[15],AE21[16],AZ21[12],

AZ31[9,17],AZ63[18],AZ91[17,19],AZ91D[20],ZE41[11],WE43

[17,21–23],LAE442[17,20],Mg–Mn–Zn[24],andMg–Ca[12,25]).

Metalionsreleasedfromcorrodiblealloystothesurrounding

tissues,maycausebiologicalresponsesinshorttermorprolonged

periods.Thetoxicityofametallicmaterialisgovernednotonlyby

itscompositionandtoxicityofthecomponentelementsbutalsoby

itscorrosionandwearresistance[26].Inasalineenvironment,

magnesium-basedalloyswouldbedegradedtomagnesiumchloride,oxide,sulphateorphosphate[3].Itisbelievedthatthe

releaseofmagnesiumionsfromcorrodingmagnesiumalloysshould

notcausetoxicity(localorsystemic),andmayevenhavebeneficial

effectsonsomeofthestructures,includingcells,intherelevantlocal

tissue[1].Yetmostofthecurrentlyinvestigatedmagnesium-based

alloys[9,11,12,17–22]forbiomedicalapplications,aslistedinTable1,

wereoriginallydesignedforindustrialapplications(inpursuitof

highstrengthandcorrosionresistance)withouttakingthe

biocompatibilityintoconsiderationsduringcompositiondesign.For

example,theabsorbablemetalstent(AMS,BiotronikGmbH),

currentlyunderclinicalinvestigation,wasreportedtobemadeofan

alloycontainingmagnesium,zirconium,yttriumandlanthanides

[3].SincetheexactcompositionofAMSstentmaterialswasnot

disclosed,itspotentialtoxicityanddegradationproductscouldnot

becompletelydetermined,thereforewereliedonthebiocompati-

bilitytestingcarriedoutbythemanufacturers[3].

Inthedesignofdegradablebiomaterials,elementswith

potentialtoxicologicalproblemsshouldbeideallyavoidedif

possible,andtheseelementsshouldbeonlyusedinminimal,

acceptableamountsiftheycannotbeexcludedfromthedesign

[27].Therefore,thetoxicelementsshouldbeidentifiedand

excludedfromthecurrentandfuturegenerationofmagnesium

alloys.AsdocumentedintheISO3116:2007[28]andEN

1753:1997*Correspondingauthor.DepartmentofAdvancedMaterialsandNanotechnology,CollegeofEngineering,PekingUniversity,No.5Yi-He-YuanStreet,Beijing100871,China.Tel./fax:þ861062767411.E-mailaddress:yfzheng@pku.edu.cn(Y.

Zheng).ContentslistsavailableatScienceDirect

Biomaterials

journalhomepage:www.elsevier.com/loca

te/biomaterials

0142-9612/$–seefrontmatterÓ2008ElsevierLtd.Allrightsreserved.

doi:10.1016/j.biomaterials.2008.10.021Biomaterials30(2009)484–498