Cartilage-tissue-engineering-PLLA-scaffold

Biomaterials26(2005)1253–1259CartilagetissueengineeringPLLAscaffoldwithsurfaceimmobilizedcollagenandbasicfibroblastgrowthfactor$ZuweiMa,ChangyouGao*,YihongGong,JiacongShenDepartmentofPolymerScienceandEngineering,ZhejiangUniversity,Hangzhou310027,ChinaReceived27January2004;accepted8April2004Availableonline21July2004AbstractApreviouslyreported‘‘graftingandcoating’’method(J.Biomed.Mater.Res.(Appl.Biomater.)63(2002)838)wasmodifiedandusedtointroducestablecollagenlayerandincorporatebasicfibroblastgrowthfactor(bFGF)onPLLAscaffoldsurfacetopreparetissueengineeringscaffoldwithimprovedbiocompatibility.Tomakethemodificationofthe3-DporousPLLAscaffoldpossible,graftingofpolymethacrylicacid(PMAA)ontothePLLAsurfacewasinitiatedbythe–OOH/Fe2+systeminsteadoftheUVlightusedintheformermethod.WatersolublecarbodimmidechemistrywasappliedtograftcollagenontothePLLAscaffoldsurface,followedbyphysicalcoatingofthecollagensolutionwithorwithoutbasicfibroblastgrowthfactor(bFGF).Surfacemodificationof2-DPLLAmembranewasalsodoneforfundamentalunderstandingofthemodification.The–COOHdensityon/inthePMAAgraftedPLLAmembrane/scaffoldwasmeasuredbycolorimetricmethodandthecollagencontenton/inthecollagenimmobilizedPLLAmembrane/scaffoldwasmeasuredbyninhydrinmethod.ChondrocyteculturingonthecollagenimmobilizedPLLAsurfacesshowedsignificantlyimprovedcellspreadingandgrowth.Incorporationoffibroblastgrowthfactorsinthecollagenlayerfurtherenhancedthecellgrowth.Thisconvenientandeffectivemethodcanbeusedtopreparebioactivescaffoldswithextracellularmatrix(ECM)-mimiccompositionfortissueengineering.r2004ElsevierLtd.Allrightsreserved.Keywords:PLLA;Surfacemodification;Scaffold;Tissueengineering;Growthfactor1.IntroductionInspiteofthegreatvarietyinthematerialsandmethodsemployedinthefabricationoftissueengineer-ingscaffolds,theprincipleforthescaffolddesigningremainsclear:thescaffoldshouldbedesignedbymimickingthenativeextra-cellularmatrix(ECM)asmuchaspossible,bothintermsofchemicalcompositionandphysicalstructure.TherolethattheECMplaysisfarmoregreaterthanjustprovidingaphysicalsupportforthecells.Itprovidesasubstratecontainingadhesionproteinsforcelladhering,andregulatescellulargrowthandfunctionbypresentingdifferentkindsofgrowthfactorstothecells.AnidealECM-mimictissueengineeringscaffoldshouldcontainbothadhesionproteinsandgrowthfactors.Syntheticbiodegradablepolymersarenowwidelyusedintissueengineeringduetotheirgenerallygoodstrengthandadjustabledegradationspeed[2].However,thechemicallyandbiologicallyinertpolymericmaterialsareunlikelytoinducecelladhesionandtissueforma-tion.Toovercomethisdrawbackofthesyntheticmaterials,naturallyoccurringpolymersextractedfromthenativeECMlikecollagenhavebeenwidelyusedtomodifythesyntheticmaterialtoimprovethecelladhesionproperties[3].Inadditiontothenaturallyoccurringstructuralpolymers,cellgrowthfactorsshouldalsobeincorpo-ratedintothetissueengineeringscaffoldtoenhancecellgrowthrateandadjustcellfunctions.AlthoughthebasicprinciplesforregulatingtheassemblyofcellsintothefunctionaltissuesarefarfrombeingwellARTICLEINPRESS$Financialsupport:TheMajorStateBasicResearchProgramofChina(G1999054305).*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddresses:[e-mail](Z.Ma),[e-mail](C.Gao).0142-9612/$-seefrontmatterr2004ElsevierLtd.Allrightsreserved.doi:10.1016/j.biomaterials.2004.04.031understood,itisclearthatthegrowthfactorsprovidepowerfultoolstocontrolmanycellularbehaviorsassociatedwithsuccessfultissueformation[4].Manymethodshavebeenusedtohybridizethegrowthfactorwithtissueengineeringscaffolds.Thechallengeliesinhowtomixthewater-solublegrowthfactorsandthehydrophobicsyntheticmaterialsevenly.Differentpro-teindeliverytechnologiessuchaswater/oilemulsiontechnique,polymermicro-spheresandpolymerhydro-gelshavebeenusedforgrowthfactordeliveryfromtissueengineeringscaffolds[5–8].Inapreviousworkweintroducedaconvenient‘‘graftingandcoating’’methodtoobtainstablecollagenlayeron2-DPLLAmembranesurfaces[1].Inthatwork,UV-inducedgraftingpolymerizationofmethacrylicacid(MAA)onPLLAsurfacewasfirstcarriedouttointroduce–COOHgroups,followedbythechemicalgraftingofcollagentypeIusingwater-solublecarbodimmideascouplingagent.Atthesametime,thephysicallycoatedcollagenwasretainedtoobtainastablecollagenlayeronthePLLAmembranesurface.Inthiswork,toextendthesurfacemodificationtechniqueto3-DPLLAscaffolds,theUV-inducedpolymerizationofMAAwasreplacedbythe–OOH/Fe2+-inducedpolymerization,whichmadethesurfacemodificationof3-DPLLAscaffoldspossible.Usingthemodifiedtechnique,stablecollagenlayerwasformedontothewallofthe3-DPLLAscaffolds.Finally,bFGFwasintroducedintothePLLAscaffoldviamixingwithcollagensolution.Chondrocyteculturingwasperformedtoevaluatethebiocompatibilityofthesurfacemodifiedscaffolds.2.Experiment2.1.MaterialsandreagentsPLLA(Mn=200,000,Mw=400,000)wassynthesizedusingthemethoddescribedin[9].PLLAmembraneswereobtainedbythesolutioncastingmethod.3-DPLLAscaffoldswithaporediameterof280–450mmandporosityof98%werepreparedusingaparaffinsphereleachingmethoddescribedin[10].Thescaffoldswerecutinto1.5
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