Magnetically-controllable-3D-microtissues-based-on

Themedissue:EmergingInvestigators2014–2868LabonaChipPAPERCitethis:LabChip,2014,14,2614Received18thJanuary2014,Accepted3rdMarch2014DOI:10.1039/c4lc00081a†WeiLiu,‡aYaqianLi,‡afSiyuFeng,bJiaNing,cJingyuWang,aMalingGou,dHuijunChen,cFengXueandYananDu*afMicrotissuesonthescaleofseveralhundredmicronsareapromisingcellcultureconfigurationresemblingthefunctionaltissueunitsinvivo.Incontrasttoconventionalcellculture,handlingofmicrotissuesposesnewchallengessuchasmediumexchange,purificationandmaintenanceofthemicrotissueintegrity.Here,wedevelopedmagneticmicrocryogelstoassistmicrotissueformationwithenhancedcontrollabilityandrobustness.Themagneticmicrocryogelswerefabricatedon-chipbycryogelationandmicro-moldingwhichcouldendureextensiveexternalforcessuchasfluidicshearstressduringpipettingandsyringeinjection.Themagneticallycontrollablemicrotissueswereappliedtoconstituteanovelseparable3Dco-culturesystemrealizingfunctionalenhancementofthehepaticmicrotissuesco-culturedwiththestromalmicrotissuesandeasypurificationofthehepaticmicrotissuesfordownstreamdrugtesting.Themagneticallycontrollablemicrotissueswithpre-definedshapeswerealsoappliedasbuildingblockstoacceleratethetissueassemblyprocessundermagneticforceforbottom-uptissueengineering.Finally,themagneticmicrocryogelscouldbeinjectedinvivoascelldeliveryvehiclesandtrackedbyMRI.Theinjectablemagneticmicrotissuesmaintainedviabilityattheinjectionsiteindicatinggoodretentionandpotentialapplicationsforcelltherapy.Themagneticmicro-cryogelsareexpectedtosignificantlypromotethemicrotissuesasapromisingcellularconfigurationforcell-basedapplicationssuchasindrugtesting,tissueengineeringandregenerativetherapy.1.IntroductionLivingtissuesareensemblesofmicroscalesubunits(e.g.lobulesintheliver,alveoliinthelungandisletsinthepancreas)containingdifferentcelltypes,extracellularmatrices,bioactivesolublefactorswithwell-defined3Darchitecturesandtissue-specificfunctions.1Consideredascapableofbio-mimicryofthenativetissuesubunits,invitroengineeredmicroscaletissues(i.e.microtissues)arecurrentlyunderthespotlightintissueengineeringandregenerativemedicine.Duetothemicroscaleprecisioninarchitecturesandcellularinteractions,microtissuesoutperformedtheconventionalcellcultureconfigurations(e.g.monolayercultureonplanarsubstrates,dissociatedcells,orcell–materialmixtures)forapplicationsincell-baseddrugscreening,2–4organprinting,5,6tissueimplantation7,8andcelltherapy.9,10Microtissueshavebeenengineeredviavariousapproachessuchasthegravity-basedhanging-dropmethodandmaterial-assistedcellularassembly.11Material-assistedmicrotissueformationenablesgreaterflexibilitiesintissuearchitecturescomparedwiththehanging-dropcounterpartwhichusuallyresultsinonlysphericalmicrotissues.Inparticular,micro-scalehydrogel-assistedmicrotissueformationiswidelyusedtoconstructtissue-likefunctionalbuildingblocks,1,12–14thankstothegoodbiocompatibilityandeaseofmicro-fabrication(e.g.micro-moldingorphotolithography)ofthehydrogel.15–17Nevertheless,microscalehydrogelssufferfromtheirunsatisfactoryload-bearingproperty,unavoidablecelldamageduetocrosslinkingagentsduringinsitupolymeriza-tionandlackofcontrollabilityofindividualmicrotissueunits.Buildingmechanicallyrobustmicrotissueunitswithdesirablecellularmicroenvironmentandversatilecontrolla-bilityremainsanunmetneedinthefieldofbiofabricationandtissueengineering.2614|LabChip,2014,14,2614–2625Thisjournalis©TheRoyalSocietyofChemistry2014aDepartmentofBiomedicalEngineering,SchoolofMedicine,TsinghuaUniversity,Beijing,PRChina.E-mail:[e-mail];Fax:[phone];Tel:[phone]bSchoolofBiologicalScienceandMedicalEngineering,BeihangUniversity,Beijing,PRChinacCenterforBiomedicalImagingResearch&DepartmentofBiomedicalEngineering,SchoolofMedicine,TsinghuaUniversity,Beijing,PRChinadStateKeyLaboratoryofBiotherapyandCancerCenter,WestChinaHospital,WestChinaMedicalSchool,SichuanUniversity,Chengdu,610041,PRChinaeMOEKeyLaboratoryofBiomedicalInformationEngineering,SchoolofLifeScienceandTechnology,Xi'anJiaotongUniversity,Xi'an,710049,PRChinafCollaborativeInnovationCenterforDiagnosisandTreatmentofInfectiousDiseases,Hangzhou,310003,PRChina†Electronicsupplementaryinformation(ESI)available.SeeDOI:10.1039/c4lc00081a‡Theseauthorscontributedequallytothiswork.Publishedon10March2014.DownloadedbyQingDaoUniversityofScienceandTechnologyon18/12/201400:36:34.ViewArticleOnlineViewJournal|ViewIssueLabChip,2014,14,2614–2625|2615Thisjournalis©TheRoyalSocietyofChemistry2014Inthisstudy,weattempttobuildrobustandcontrollablemicrotissuesbasedonnovelmagneticmicrocryogels,whichintegrateourrecentlydevelopedmicrocryogels10withmagneticnanoparticles(MNPs).Microcryogelsaremicroscalemacroporouscryogelssynthesizedon-chipbycryogelationandmicro-molding