MIT生物医学工程课件1

13.051J/20.340JLecture1:Intro.toBiomaterials:StructuralHierarchyinMaterials&BiologyWhatare“biomaterials”?Agoodworkingdefinitionfromthetextis:“Anonviablematerialusedinamedicaldevice,intendedtointeractwithbiologicalsystems.”*MEDICALDEVICEEXAMPLESANNUAL#(U.S.)*Sutures(temporaryorbioresorbable)250M**Catheters(fluidtransporttubes)200MBloodBags40MContactLenses30MIntraocularLenses2.5MCoronaryStents1.2M***KneeandHipProstheses0.5MBreastProstheses(cancerorcosmetic)0.25MDentalImplants0.9MRenalDialyzers(patients)0.3MOxygenators/CPB’s(cardiopulmonarybypasssystem—0.3Mfacilitatesopenheartsurgery)VascularGrafts0.3MPacemakers(pulsegenerators)0.4MBiomaterialsaredefinedbytheirapplication,NOTchemicalmake-upEx.IntraocularlensesComposition:poly(methylmethacrylate)PMMA,a.k.a.“acrylic”Properties:•HighrefractiveindexUsedasauto•Easilyprocessedtaillightcoversforthesamereasons!•Environmentallystable(relativelyinert)•Goodmechanicalproperties*fromBiomaterialsScience:AnIntroductiontoMaterialsinMedicine,2nded.,B.D.Ratneretal.,eds.,Elsevier,NY2004**fromBiomaterialsScience:AnIntroductiontoMaterialsinMedicine,1sted.,B.D.Ratneretal.,eds.,Elsevier,NY1996***fromIntroductiontoBiomedicalEngineering,2nded.,J.Enderleetal,,eds.,Elsevier,NY200523.051J/20.340JBiomaterialscoverallclassesofmaterials–metals,ceramics,polymersPLA=polylactidePGA=polyglycolidePDO=poly(p-dioxanone)PUR=polyurethaneePTFE=expandedpolytetrafluoroethylenepolyethylenePET=polyethyleneterephthalateEar:HA,Al2O3,Ti,siliconeTi,Ti-Al-V,Al2O3,HA,Bioglassacrylic2O3,HA,TCP,HA/PLA,Bioglass,Ti,Ti-Al-VCranial:316LSS,Ti,acrylic,HA,TCPBloodvessels:ePTFE,PETC,ePTFE,PET,PURPLA,PGA,PCL,PTMC,PDOOcularlenses:acrylates,siliconeBoneFixation:316LSS,Co-Cr-Mo,Ti,Ti-Al-V,PLA/HA.,PLA,PGALoad-bearingOrthopedic:Al2O3,Zirconia,316LSS,Ti,Ti-Al-V,PTMC=polytrimethylenecarbonateUHMWPE=ultrahighmol.wt.Dental:acrylic,gold,316LSS,Co-Cr-Mo,Prostheticjoints:316LSS,Co-Cr-Mo,Ti,Ti-Al-V,silicone,UHMWPE,Maxillofacialreconstruction:AlHeart:Co-Cr-Mo,Ti-Al-V,pyrolyticPacemaker:316LSS,Pt,PUR,silicone,PETDegradableSutures:copolymersofTendon&Ligments:PLA/Cfiber,ePTFE,PET,UHMWPECo-Cr-Mo,UHMWPESpinal:Co-Cr-Mo,Ti,HA,UHMWPEHA=hydroxyapatiteSS=stainlesssteelFigurebyMITOCWinterface33.051J/20.340JWhatgovernsmaterialschoice?Historically⇒TodayToday⇒Future1.Bulkproperties:matchedtothoseofnaturalorgans•Mechanical(ex.,modulus)•Chemical(ex.,degradation)•Optical(ex.,whiteness,clarity)2.AbilitytoProcess3.FederalRegulations:MedicalDeviceAmendmentof’76(allnewbiomaterialsmustundergopremarketapprovalforsafetyandefficacy)EngineeringParadigm?Rationaldesignofbetterunderstandingofmaterial/biologicalAdoptionoftheMaterialsbiomaterialsbasedonnaturalmaterialsandtheorganisminterfaceApplication(Performance)PropertiesStructureProcessingWhatis“structure”?thearrangementofmatterBothsyntheticmaterials&biologicalsystemshavemanylengthscalesofstructuralimportance.3.051J/20.340J4StructuralHierarchiesSyntheticMaterialsLivingOrganismsChemicalPrimaryStructure10-10mMolecules(H2O,peptides,salts…)HigherOrderStructureOrganelles(lysosomes,nucleus,mitochondria)MicrostructureCellsComposites10-3mTissuesPartsOrgansDevicesIndividualsBiomaterialsEngineeringspans~8ordersofmagnitudeinstructure!TherealmofbiomaterialsengineeringCa++Ca++Ca++Ca++Ca++Ca++Ca++Ca++Ca++Ca++Ca+Ca++extracellularenvironmentlipidmembranecytosolFibroblastcellsalignedonmicro-patternedsurfaceEngineeredlengthscale:10-3to10-6mCelladherestoRGDpeptideclusterslinkedtocombcopolymerchainendsEngineeredlengthscale:10-7to10-8mCelladhesionreceptorsembeddedinmembraneinteractwithRGDsequenceEngineeredlengthscale:10-9to10-10m53.051J/20.340JLENGTHSCALESOFSTRUCTURE1.PrimaryChemicalStructure(Atomic&Molecular:0.1–1nm)Lengthscaleofbonding–stronglydictatesbiomaterialperformancePrimary•Ionic:e-donor,e-acceptorceramics,glasses(inorganic)•Covalent:e-sharingglasses,polymers•Metallic:e-“gas”aroundlatticeof+nucleiSecondary/Intermolecular•Electrostatic•H-bonding•VanderWaals(dipole-dipole,dipole-induceddipole,Londondispersion)•HydrophobicInteractions(entropy-drivenclusteringofnonpolargpsinH2O)•PhysicalEntanglement(highMWpolymers)Ex.1:aluminaAl2O3usedforhardtissuereplacement–(corundum)e.g.,dentalimplantsProperties:•corrosionresistant•highstrengthderivedfrom•wearresistantionicbondingElectrostaticinteractionsw/chargeson•“biocompatible”proteins⇒non-denaturedadsorbedproteinlayer⇒“camouflage”:CourtesyofBICON,LLC.().Usedwithpermission.3.051J/20.340J6Ex.2:polyethyleneoxide(PEO)(CH2CH2O)nusedforproteinresistantcoatings,hydrogelsProperties:•flexible••watersoluble•bioinertsecondarybondingStrongH-bonding,unique3n.n.coordinationw/H2O⇒⇒hydrolysableDerivedfromprimary&water-likelayer“camouflage”proteingraftedPEOdenaturedproteinTakeHomeMessage:“Biocompatibility”isstronglydeterminedbyprimarychemicalstructure!Biocompatibility:“abilityofamaterialtoperformwithanappropriatehostresponse”ProteinAdsorptionCellAttachmentCellSecretionChemicalStructureHostResponse73.051J/20.340J2.HigherOrderStructure(1–100nm)Cryst