Cell adhesion and mechanical properties of a flexible scaffold for cardiac tissue engineering

ARTICLEINPRESS

ActaBiomaterialiaxxx(2007)

xxx–xxx

Briefcommunication

Celladhesionandmechanicalpropertiesofa exiblesca oldfor

cardiactissueengineering

L.A.Hidalgo-Bastidaa,J.J.A.Barrya,N.M.Everittb,F.R.A.J.Rosea,L.D.Butterya,

I.P.Hallc,W.C.Claycombd,K.M.Shakeshe a,*

c

DivisionofDrugDeliveryandTissueEngineering,SchoolofPharmacy,UniversityofNottingham,NottinghamNG72RD,UK

Bioengineering,SchoolofMechanical,MaterialsandManufacturingEngineering,UniversityofNottingham,NottinghamNG72RD,UK

DivisionofTherapeuticsandMolecularMedicine,SchoolofMedicalandSurgicalSciences,UniversityHospitalNottingham,NottinghamNG72UH,UK

d

BiochemistryandMolecularBiology,SchoolofMedicineatNewOrleans,LouisianaStateUniversity,BatonRouge,LA,USA

b

a

Received21March2006;receivedinrevisedform7December2006;accepted12December2006

Abstract

Cardiactissueengineeringisfocusedonobtainingfunctionalcardiomyocyteconstructstoprovideanalternativetocellularcardio-myoplasty.Mechanicalstimulihavebeenshowntostimulateproteinexpressionandthedi erentiationofmammaliancellsfromcon-tractiletissues.Ouraimwastoobtaina exiblesca oldwhichcouldbeusedtoapplymechanicalforcesduringtissueregeneration.Poly(1,8-octanediol-co-citricacid)(POC)isanelastomerthatcanbeprocessedintosca oldsfortissueengineering.Weinvestigatedthee ectofmodifyingtheporosityonthemechanicalpropertiesofthePOCsca olds.Inaddition,thee ectsofthestoragemethodandstrainrateonmaterialintegritywereassessed.ThemaximumelongationofPOCporous lmsvariedfrom60%to160%oftheiroriginallength.Adecreaseintheporositycausedariseinthiselasticmodulus.TheattachmentofHL-1cardiomyocytestoPOCwasassessedon lmscoatedwith bronectin,collagenandlaminin.Theseextracellularmatrixproteinspromotedcelladhesioninapro-tein-type-andconcentration-dependentmanner.Therefore,POCsca oldscanbeoptimisedtomeetthemechanicalandbiologicalparametersneededforcardiacculture.Thisporousmaterialhasthepotentialtobeusedforcardiactissueengineeringaswellasforothersofttissueapplications.

Ó2007ActaMaterialiaInc.PublishedbyElsevierLtd.Allrightsreserved.

Keywords:Sca old;Poly(1,8-octanediol-co-citricacid)(POC);Elastomer;Cardiomyocyte;Tissueengineering

1.Introduction

CardiovasculardiseaseshavebecomethemaincauseofdeathnotonlyinWesterncountriesbutalsoinmanydevel-opingnations[1].Currenttherapiesforcardiacfailure(withtheexceptionofcardiactransplantation)ingeneralprovidelimitedimprovementsincardiacoutputandrelatedsymp-toms.Cardiactransplantation,thebesttherapyavailable,isrestrictedbytheshortageofdonorsandtheriskoftissuerejection.Recentresearchhasconcentratedonnewalterna-tives,suchascardiaccellularmyoplasty,whichcould

Correspondingauthor.Tel.:+441159515104.

E-mailaddress:kevin.shakeshe @nottingham.ac.uk(K.M.Shake-

she ).

*potentiallyimproveoutcomesintermsofbothmorbidityandmortality[2].Apotentialalternativetreatmentcouldbeachievedbyusingaphysicalsupportcontaininggrowthfactorscapableofinducingspeci ccellulardi erentiationtogenerateanengineeredcardiacconstruct.Aninitialchal-lengeofgeneratinganengineeredcardiacpatchisthedevel-opmentoftheidealbiomaterialforcardiomyocyteculture.Researchershaveproposedbothsyntheticandnaturalmaterialstogenerateasuitablecardiacgraft.Naturalpoly-merssuchascollagenwere rstusedforcardiacsca olds,buttheyexhibitedlimitedmechanicalpropertiesandbatch-to-batchvariation[3].RadisicandVunjak-Novako-vicstatedthatcollagenisnotacandidateforcardiacscaf-foldsbecauseofits‘‘poorstructuralintegrity’’[4].Syntheticpolymershavealsobeeninvestigated;Bursac

1742-7061/$-seefrontmatterÓ2007ActaMaterialiaInc.PublishedbyElsevierLtd.Allrightsreserved.doi:10.1016/j.actbio.2006.12.006

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L.A.Hidalgo-Bastidaetal./ActaBiomaterialiaxxx(2007)xxx–xxx

etal.assessedthree-dimensional(3-D)spinner askcultureofprimaryratheartcellsseededontopoly(glycolicacid)(PGA) bres.Theirresultsshowedthattheywereabletogenerateaconstructwhichwasfunctionalforthe rst3days,includingnormalproteinexpressionofcardiacandmusclemarkerssuchastropomyosinandactin,cell-to-cellconnectionsandspontaneouscontractions,butthisactivitydecreasedinthefollowing4daysofculture(days4–7)[5].Biodegradableelastomericpolymericmaterialshavealsobeenassessedbecausetheirmechanicalpropertiesmeettheforce-generatingdemandsofcontractiletissue.Polyure-thaneelastomersweresynthesisedwiththeuseofalysine-baseddi-isocyanate,polycaprolactoneandaphenylalaninechainextender.Inthissystem,themorphology,stabilityanddi erentiationofcardiomyocytesweresimilartothoseculturedonnon-elastomericpolystyreneorglass[6].

Furtherchallengesforthesystemaretheinvitrocultureconditions,suchasmechanicalorelectricalstimuli,thatcouldbeapplied.Studiesusingvariousbiomaterialsandcul-turesystemshavedemonstrateddi erente paredthee ectandqualityofcar-diomyocyteculture,inbothspinner asksandrotatingves-sels,onPGAdisksthatwerenon-coatedorcoatedwithlaminin.Followingaperiodoftimeinculture,theconstructswereassessedforproteinexpressionconnexin43(Cx43),myosinheavychain(MHC)andcreatinekinaseMM(CK-MM),aswellaselectrophysicalpropertiesunderstimula-tion.Theyshowedthatcardiomyocytesculturedinarotat-ingbioreactorpossessedenhancedviability,electricalcouplinganddi erentiationbecauseofthelaminar owcon-ditionsoftherotatingvesselcomparedwiththeturbulentenvironmentofthespinner ask[7].Di erentmechanicallystimulatedculturesystemshavebeenshowntoin uencetheproliferation,proteinexpressionandmorphologyoftheculturedcellsandtoimpactdirectlyontheresultantstructureandpropertiesofcardiacconstructs.Solanetal.[8]investigatedamechanicalstimulatedenvironmentusingatubularPGAsca oldinastirredbioreactorwithamediapulsatilesystem,whichinducedincreasedlevelsofcollagendepositionintheconstructs.Ruwhofetal.[9]describedhowthee ectofmechanicalstressisakeyfactorinthedevel-opmentofhaemodynamicoverload-inducedcardiachyper-trophyandthereforeinthedevelopingofcardiacconstructs.ThisgroupusedtheFlexercellTMStrainsystemtoculturecardiomyocytesundercyclicstretchconditionstoanalysegrowthfactorandhormonereleaseasaresponsetothemechanicalforce.Cardiomyocytessecretedhighlevelsoftransforminggrowthfactorbeta(TGFb)andatrialnatri-ureticfactor(ANF)whensubjectedtothesekindofforces.Also,Akhyarietal.[10]concludedthatamechanicalregi-mencouldimprovetheformationof3-Dtissue-engineeredcardiacgraftbypromotingtheproliferationanddistributionofcardiaccellsandbystimulatingorganisedmatrixforma-tion.Theyshowedthatcardiacconstructsculturedwhilstbeingstretchedexhibitedanincreasedamountofcollageninthematrixcomparedwiththosethatwereculturedstatically.

Inthispaper,ouraimwastoobtainaporous exiblesca oldtowhichmechanicalforcescouldbeappliedduringinvitroculturetoengineeracardiacpatchforinvitroandclinicaluse.Recently,Yangetal.[11]suggestedtheuseofapolyester,poly(1,8-octanediol-co-citricacid)(POC),toproduceelasticsca olds.Thispolymerdisplayedmechani-calstrength,suitabledegradationratesandcytocompati-bility,allofwhichcouldbetailoredbythemodi cationofthesynthesisconditionsandofthemolecularratiosofthemonomers.Wechosetoinvestigatetheuseofthispoly-mertogenerateasca oldforcardiacmuscleregeneration,suitableforitsuseinamechanicalstimulatedsystem.Herewedescribecardiomyocyteattachmentandsurvivalonthin lmsofthispolymer,themethodologyofsca oldfabrica-tionandtheresultingmorphologicalandbiomechanicalpropertiesofthematerial.2.Experimental

2.1.Poly(1,8-octanediol-co-citricacid)synthesis

Equimolarquantitiesof1,8-octanediol(Sigma,UK)andcitricacid(Sigma,UK)wereaddedtoaround-bot-tomed ask.Themixturewasmeltedbystirringat160°Cinapara nbathafterwhichtimethetemperaturewasloweredto140°Candthestirringconditionsandtemperaturewereheldforafurther20min[10].Thepre-polymersolutionwasallowedtocooltoroomtem-perature(RT)andthendissolvedinacetone(Sigma,UK)at33.3%(w/v)solutionandstirredfor48htodecreasetheviscosity.Thepre-polymersolutionwaspouredintoapoly(tetra uoroethylene)(Te on)mouldtoobtaineitherdiscs(10mmdiameter)orrectangularsca olds(56mm·24mm·2.5mm)andcross-linkedinanovenat80°Candatmosphericpressurefor2weekstoobtainPOC lms.

2.2.Fabricationandmodi cationofsca olds

POCsca oldswereprocessedbysalt-leachingtoobtainaporousstructure.Brie y,thePOCpre-polymer/acetonesolutionwaspouredintoaTe onmould(discorrectangu-larshape;seeabove)containingsievedsodiumchloride(Sigma,UK)andcoveredtoallowthesalttosoakfor30min.Theacetonewasallowedtoevaporateo for24hatroomtemperature,afterwhichthesamplesweretransferredtoanovenforthecross-linkingstagefor2weeksat80°C.Thesca oldswerecastoutandwashedsev-eraltimesindistilledwaterfor3daystoremoveallthesaltparticles.ThemonomerresidueswerethenwashedoutinPBStoadjustthepHtophysiologicallevels.Thematerialwaseitheroven-driedat80°Cfor2handstoredatroomtemperatureorstoredatÀ20°Candfreeze-driedovernightbeforeuse.Theporositywastailoredbyanincrementordecrementofthesaltcontenttoobtaina nalporosityof60%,70%or80%.

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2.3.Sca oldcharacterisation

Theresultantmorphologyofthesca oldswasanalysedintriplicatebyscanningelectronmicroscopy(SEM)atlowandhighvacuum(JEOLUKLtd.),heliumpicnometry(Micromeritics,UK)andmicrotomography(lCT-40,Scanco,UK)aspreviouslydescribed[12].TensiletestswereconductedintriplicateonaTA.XTplusTextureAnalyser(StableMicroSystemsÒ)withaloadcellof5kg,usingpneumaticclampstosecurethesamples.Brie y,thesample(8mm·54mm·2.5mm,length·width·thickness)wastestedatfourdi erentrates:18,180,300and500mmminÀ1.Strain,stressandtheengineeringYoung’smodulusvalueswereobtainedusingthepackageTextureExponent32Ò(StableMicroSystems).Thesametextureanalyserwasusedtoevaluateintriplicatethefatigueoftheporousmaterialover1000cyclesat300mmminÀ1,60%strainandatafrequencyof0.27Hz.

InvitrodegradationwasevaluatedbyweightingdryPOCsca oldsamples(8mm·54mm·2.5mm,length·width·thickness),placingtheminacontainerwith20mlofPBSandincubatingthemat37°Cforupto6months.SpecimenswerewashedasrequiredtomaintainapHof7.2.Afterincubationsampleswereoven-driedandweighedtoassessthelossofdry-weight.2.4.CellcultureofHL-1cells

ThemousecardiacmusclecelllineHL-1wasgrownat37°Cinahumidi edatmosphereof5%CO2inairinClay-combmedium(JRHBiosciences,USA)supplementedwith10%(v/v)foetalbovineserum(JRHBiosciences,USA),0.1mMnorepinephrine(Sigma,UK),2mMglutamine(Sigma,UK)and100UmlÀ1/100lgmlÀ1penicillin/strep-tomycin(Sigma,Poole,UK).HL-1cellswereseededintogelatine/ bronectin(Sigma,Poole,UK)pre-coatedT-25andT-75cellculture asksasdescribedpreviously[13].Themediumwaschangedevery24h.Serialpassagesweremadebytrypsination,centrifugationandre-suspensionofpelletsofsub-con uentmonolayersandthenre-platedatadilutionof1:3.

2.5.Cellseedingonpolymer lms

POC lmswerecutintosquares(0.70cm2)andsterilisedbyincubationinasolutionof10%(v/v)antibiotics/antimycoticsfor1h,washedwithsterilePBS,incubatedin70%(v/v)ethanolfor30min,washedagainand nallysterilisedbyultraviolet(UV)lightexposurefor15mineachside.ProteinsolutionswereusedtocoatthePOC lmsbypassiveadsorption.Brie y,POC lmswereincubatedina bronectin(400,40and4lgcmÀ2),collagen(10,1and0.1lgcmÀ2)orlaminin(2,0.2and0.002lgcmÀ2)solutionovernightat4°CandwashedthreetimesinPBSpriortoincubationwithcells.CoatedPOC lmswerethenseededwith1·106HL-1cellscmÀ2.Afterincubatingfor18h,sampleswerewashedthreetimesinPBSfor5min.For

morphology,cellsadherenttothe lmwereimagedusingaLEICAmicroscope.Thenumberoflivecellsinaran-domlydelimitedareawasanalysedintriplicateusinganimageanalysispackage(LeicaQWin,UK)tocalculatecellareacoverage.Survivalwasdeterminedby uorescentstainingofthesamples.Brie y, lmswereincubatedfor30minwith1.05lmollÀ1calceinAMand4.0lmollÀ1ethidiumhomodimer(Live/Deadstain,MolecularProbes,UK)andthenvisualisedunderUVlight.3.Results

3.1.HL-1adhesiontoPOC lms

HL-1celladhesionwasassessedonthePOC lms,bothuncoatedandcoatedwith bronectin,collagenorlaminin,followingovernightincubation.MonolayercultureofHL-1cellsonPOCshowedapoorattachmenttothesurfaceofuncoated lms,coveringnomorethan10%ofthearea.CellsseededonPOC lmscoatedwith bronectinattachedtothesurfaceandproliferatedmorerapidlythanthoseseededoncollagen-andlaminin-coated lms.Fibronectinusedataconcentrationof400lgcmÀ2showeda90±5%HL-1cellareacoverage,incontrastto32±4%withthesameproteincoatedat40lgcmÀ2andto11±1%whentheconcentrationofthe bronectinwasthelowest,at4lgcmÀ2.Ofparticularnote,laminindidnotsupportcompletedi erentiationintothecardiomyo-cytemorphologyasafterthistimesomeofthecellspossessedaroundedmorphologyratherthanthecharac-teristicellipticalshape.Weobservedthat,becausethecellsinlaminin-coated lmsdidnotspreadtoanormalphysiol-ogyasthecellsintheothertwosurfaces,theirtotalareacoveragewasa ected.Inourexperiments,cellcoveragealsodecreasedastheproteinconcentrationreduced,reach-ingthesamelevelsofattachmentasuncoated lmswiththelowestconcentrations(Fig.1a).

3.2.CharacteristicsofPOCprocessedsca olds

POCprocessedbysalt-leachingresultedinporousstruc-tureswithinter-connectedpores(Fig.1bandc)intherangeof340–380lm,withameanporesizeof360±20lm(asdeterminedbySEMandmicrocomputedtomography)forallthreeporosities.Porosity,evaluatedwithmicrocomputedtomographyandheliumpycnometry,wascon rmedtobe60±3%,70±4%or80±3%(±SD).POCsca oldsdegraded50±6%in3monthsandreportedalossofdry-weightofatleast90%after6months.

Mechanicaltestswereperformedatroomtemperatureonsca oldspreviouslystoredatÀ20°Candatroomtem-perature;eachsetincludedsamplesofthreedi erentporos-ities:60%,70%and80%.WefoundthattheYoung’smodulusofthesamplesstoredatroomtemperaturerangedfrom0.2to3.3kPa,comparedwiththeYoung’smodulusofPOCsca oldsstoredatÀ20°C,whichrangedfrom0.1to1.7kPa(Fig.2aandb),dependingontheporosity

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Fig.1.(a)TotalareacoverageofHL-1cellsafter18hofcultureonPOC lmscoatedwith bronectin,collagenorlaminin(n=3,errorbarsrepresents+SD);(b)porousstructureofaPOCsca oldwithinter-connectedporesasshowninSEMofthesurfaceandin(c)microcomputedtomography

scan.

Fig.2.Young’smodulusofPOCsca olds,storedat(a)À20°Cand(b)atroomtemperature,testedat18,180,300and500mmminÀ1.MaximumelongationatbreakofPOCsca olds,storedat(c)À20°Cand(d)atroomtemperature,testedat18,180,300and500mmminÀ1(n=3,errorbarsrepresents+SD).

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ofthematerialandonthestrainrateduringthetests.ThemaximumelongationforPOCsca oldsstoredatRTwerefoundtobebetween60%and95%,whilethesca oldsstoredatÀ20°Cexhibitedanelongationatbreakfrom60%to165%oftheiroriginallength,dependingalsoontheporosityandthestrainrate(Fig.2candd).Fatigueevaluation,testedin60%porousPOCsca olds,showedthatafter1000cyclesofcontinuousstretchingtherewerenosignsofpermanentdeformationorfailure.4.Discussion

PriortofabricatingandcharacterisingPOCsca oldsfortissueengineering,weneededtocon rmtheadhesionofcardiomyocytestothispolymerandtodetermineifextracel-lularmatrix(ECM)proteincoatingwouldberequiredtoimprovethecellattachment.AfterobservinglowlevelsofattachmentofHL-1cellsonuntreatedPOC lms,wecoatedthematerialwiththreedi erentECMproteins: bronectin,lamininandcollagen.Weobservedanimprovementincellattachmenttothepolymerwithallproteins.ThehighesttotalareacoverageofHL-1cellswasobtainedwith bronec-tin-coated lmsincomparisonwithcellsculturedoncolla-genandlaminin.PreviousstudieshavealsoshownthatECMproteinsin uencecardiaccellmorphologyandphys-iology.Lundgrenetal.foundthat,after2weeksofculture,myocytesseededondishescoatedwithcollagenandlamininformedadensermonolayerthanthoseculturedonuncoatedplasticdishes,andalsoexhibitedspontaneouscontraction[14].Wefoundthat bronectinwastheoptimalECMpro-teintoenhancecelladhesiontothePOC lm.Thiscouldpossiblyberelatedtothefactthatahigherlevelof bronec-tinexpressionisassociatedwithcellproliferationandmigra-tionattheembryonicstageofheartdevelopment,whileduringheartgrowth bronectinlevelsdecrease,andlamininandcollagenlevelsincrease[15].

OncecelladhesiontoPOChadbeencon rmed,thenextstagewastoestablishamethodologytofabricate exibleporoussca olds.Thesesca oldswerethencharacterisedintermsofporosityandporesize,andmechanicalpropertiestoevaluatethesuitabilityofthesematerialsasasupportforcellcultureinastretchingbioreactor.Withrespecttomechanicalproperties,theelongationatbreakfoundinthesesca oldswasintherangeof60–165%whiletheYoung’smodulusvariedbetween0.2and3.3kPa,alldepen-dentontheporosity,thestrainrateofthetestandthestor-agemethod.Therewasnoclearlinkbetweenthemaximumelongationsofthedi erentsca oldsandtheparametersmodi ed.Porosity,strainrateandstoragemethoddidnota ectthestretchingpropertiesofthematerial.InitialworkonthemechanicalpropertiesofPOC lmsfoundthattheelastomerhasanultimateelongationof260%andaYoung’smodulusof2.6MPa[11];however,sca oldsfabricatedwithPOCforsofttissueapplicationshowedadecreasedelonga-tionoflessthan100%andaYoung’smodulusof0.5MPa[16].Wealsofoundthat,afterprocessing,themechanicalpropertiesofthesesca oldswereweakenedbythepresenceofpores,ourPOC lmsexhibitingaYoung’smodulusthatrangedfrom1.5to3.3kPa.AlterationsintheYoung’smod-uluswereobservedwhenthestrainrateandtheporosityweremodi ed.AnincrementofthestrainrateduringthetestscausedanincreasedYoung’smodulusinallthespeci-mens.Thisiscongruentwiththiselastomer,asanaug-mentedstrainrateequalsalowertemperatureandthereforeasti ermaterial.Inaddition,theYoung’smodu-lusdecreasedinsca oldswithhigherporosity,decreasingfrom3.5to1.5kPafor60–80%poroussca oldsrespec-tively,allstoredatroomtemperatureandtestedat500mmminÀ1.Thiswasattributedtoareducedproportionofsolidmaterialinthesca oldsandahighpercentageofvoidsduetoporesweakeningthemechanicalproperties,resultinginlesssti structures.Thedi erencesintheYoung’smodulusbetweensca oldsstoredatroomtemper-atureandthosestoredatÀ20°Cwereprobablyduetothecontinuedcross-linkingduringstorageatroomtemperaturewhichdidnotoccuratÀ20°C.Thesti nessoftheleftven-tricleofthehearthasbeencalculatedat31kPa[17],whichissimilartothevaluesfoundforourporouspolymersca old,suggestingthatthesematerialscouldbesuitableforuseincardiactissueengineering.Studiesusingotherbiodegrad-ableelastomershavereportedsimilarmechanicalpropertiestoproteinsfoundinhumantissues.Wangetal.[18]synthes-isedabiocompatiblebiodegradableelastomer,poly(glycerolsebacate),thatexhibitedalowYoung’smodulusof0.28MPaandaminimumelongationof267%.Flexiblepoly(esterurethane)urea(PEUU)/collagensca oldswereelectrospunbyStankusetal.[19]toassessthee ectofcolla-genconcentrationonthemechanicalpropertiesofthissoftmaterial.Adecreaseinthetensilepropertiesfromaninitialmodulusof8–2MPawasfoundinsca oldswith90%con-tentofcollagen,butthebreakingstrainwasincreasedfrom220%to270%.Softmaterialswithhighstrains,suchasPGS,PEUUandPOC,canbeexploitedforsofttissueapplica-tions,whereasotherelastomericpolymers,suchasP4HB,withahighelasticmodulusof250MPa,maynotbesuitableforthis[20].Therearefewreportsonthemechanicalchangesofbiodegradableelastomericsca oldsovertime.Inarecentpaper,Guanetal.[21]reportedtheuseofporousPEUUsca oldsforsofttissueengineering.Thesebiode-gradablepolyurethanesca oldsexhibitedbreakingstrainsfrom214%to294%andtensilestrengthof0.97–1.64MPa,but,mostimportantly,itwasshownthattheirmechanicalpropertiesdecreasedafter2weekstoabreakingstrainof150%andatensilestrengthof0.8MPaduetopolymerdeg-radation.MechanicalpropertiesofpartiallydegradedPOCsca oldsareyettobedetermined.

Thesca oldspresentedhere,whichdisplayedamaximumelongationatbreakbetween60%and160%,willbeusedinfuturestudiestoculturecardiomyocyteswithinastretchingbioreactorforwhichwewantedtogenerateamaterialwithaminimumelongationof20%,basedonpreviousstudies[22].Althoughthemaximumelongationofthehumanheartvar-iesfrom20%to90%,theaverageis60%[23,24].POCscaf-foldsachieved60%ofmaximumelongationasaminimum

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andthereforethismaterialcomplieswiththephysiologicalparametersrequired.Inadditiontothis,these exiblescaf-foldsalsoexhibitedareasonabledegradationpro le.5.Conclusions

ThispaperdescribesinitialstudiesintothesuitabilityandfabricationofporousPOCsca oldsforcardiacmuscleengineering.HL-1cellsculturedonPOC lmsexhibitedanincreasedlevelofadhesiontothematerialswhenpre-coatedwithECMproteins,with bronectino eringthebestadhesionproperties.POCwasprocessedbysalt-leachingtoobtainporousstructureswithcontrollablecharacteristicssuchasporesize,porosityandshapetomeetthemechanicalpropertiesrequiredforcardiacpatchengineering.Overall,thePOCsca oldsgeneratedinthisstudyexhibitedreliablemechanicalpropertiesandsup-portedcelladhesionwhencoatedwithECMproteins.Webelievethatthese exiblesca oldswillsupportthecul-tureofcardiomyocytesinamechanicallystimulatedenvi-ronmenttoimprovecellulardi erentiationandproteinexpression,ahypothesisthatwearecurrentlyaddressingusingHL-1cellsandastretchingbioreactor.Acknowledgements

Wewouldliketogratefullyacknowledgefundingsup-portfromtheMexicanScience&TechnologyCouncil(CONACYT—Mexico),theMexicanMinistryofEduca-tion(SEP—Mexico)andtheBritishCouncil.References

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