Bioglass-for-bone-tissue-engineering

Presentedby:IndranKanisanPackeryLiangZiyangXuTianyiSchoolofChemicalandBiomedicalEngineeringLecturer:Asst/ProfKimDhonghwanDateofPresentation:18thOctober2011IntroductionBoneTissueEngineeringBioglassBioactiveGlassScaffoldsDevelopmentsFutureWorkConclusionTissueengineering-combinationofmedicine,biologyandengineeringtocreatebiologicalsubstitutestorestore,maintainandrepairtissueinbodyQualityoflifeimprovedUsesbiologicaltissuesdirectlyfrompatientIntegrationwithtissuesisenhancedandnorejectionoccursUltimategoalistoreplaceorganandtissueinfutureReductionofoperationalandtransplantationcostsTissueengineeringScaffoldsDiscoveredin1998Scientistextendedtelomeres-endsectionofDNATelomeres-controlcelldivisionandabletoextendCreatedimmortalizedcellsthatcoulddividecontinuously3approachestoTissueEngineering•Growthofcellsin3-Dscaffolds•Deliveryoftissueinducingsubstances(growthanddifferentiationfactors)•UseisolatedcellsorcellsubstitutestoreplacecellsthatsupplytheneededfunctionPartofendoskeletonofvertebratesSupportandprotectionoforgansinbodyRigidandhoneycombstructureComposedofspongyandcompactboneSpongybone-spongelikespaces,noosteonsCompactbone-solid,densecontainosteonsCreationofbiologicalsubstitutestorestoreandmaintainfunctionofboneDifferentfromdrugtherapyorpermanentimplantsEngineeredbonebecomesintegratedwithpatientLeadstopermanentcureofdiseasedstateCurrentmethodstoreplaceboneincludeallografts,autograftsandmetallicreplacementsDevelopmentofbonetissuescaffoldsBonescaffoldshouldallowtissuestointegrateasbonescaffolderodesBoneScaffoldshouldaddress•Permitboneintegrationintoscaffold•Promotebioactivityandsterilization•Doesnotcausechronicinflammation•EnhanceosseointegrationandosteoinductionBonetissueengineeringstrategiescanrangefromacellularscaffolds,stemcelltherapycelltransplantation,andgenetherapy2Strategies•MSCs(Mesenchymecells)areisolatedandimplantedonasyntheticscaffoldtoproduceECM(extracellularmatrix)ontothescaffold•Implantationsofacellularscaffoldsafterbonesurgery/removalimmediately®Bioactiveglasses(Bioglass®)comprisingofSiO2,Na2O,CaOandP2O5inspecificproportions.Proportionsaredifferentfromtraditionalsoda-limeglassesBioglasseshavedifferentformulationsSomebindtoboneandsofttissues(45S5)Sometoboneonly(5S4.3)®ProfLarrydevelopedBioglass®(45S5)in1965DevelopedamaterialtoregenerateboneinwarvictimsCompositioniseutecticKeycompositionof60%SiO2,highNa2O,CaOratiosHighCaO/P2O5ratiochosen,closetoeutecticpoint2categoriesofBioglass®•ClassA-osteogeneticandosteoconductivematerials.Theybindwithsofttissuesandbone•ClassB-onlyexhibitosteoconductivepropertiessuchashydroxyapatite(HA).Theycannotbindwithsofttissues.AdvantagesofBioglasses•Excellentbioactivityindex•Goodmechanicalcompetence•Biodegradability®®CeramicBallVasculargraftDentalCompositeBonefillingmaterialforbonedefectsBioglass®ScaffoldTetraethylorthosilicate(TEOS)isusedasasilicaprecursor(compoundthatparticipatesinthechemicalreactionthatproducesanothercompound)Si(OC2H5)4+2H2O→SiO2+4C2H5OH(ethanol)•Triethylphosphate(TEP)andsaltcalciumnitrateaddedduringthemixingphasetointroducephosphateandcalcium•Asolisformed•SolLiquidincontinuousstate•SolidnanoparticlesaredispersedthroughouttheliquidinasolSilicaspeciesinthesolthenundergopolycondensationtoformanetworkofsilica(Gel)Thegelisthenheattreatedtodriveoffthecondensationby-productsofwaterandethanolandtoremovethenitratesSolisfoamedbyvigorousagitationintheairwiththeaidofasurfactant•Surfactantensuresthatthesurfacetensionofthesolisloweredevenly•Allbubbleswithinthesolare≈samesize•StabilizestemporallyGelationisneededtostabilize•Takes3days•TohastenHydrofluoricacid(HF)isadded3daysminutes•Bubblesarepermanentlystabilizedassilicanetworkisformedaroundthemduringcondensation.FormationofthesilicanetworkcausesthebubblestoshrinkandbringsneighbouringbubblescloserDuringthecondensationphase,•Interstitialpores(filledwithby-productsofwaterandethanol)betweenthenanoparticlesofthesilicanetworkRemovedintheageinganddryingphasebyheattreatingNitratesarealsoremovedinthisprocessThesilicanetworkshrinksfurther,rupturingandopeningupinterconnectivitybetweenthemacroporesDeterminingofmacro/nanostructureofthescaffoldisimportant•MacroporesBoneandbloodvesselgrowth•NanoporesFortailoringdegradationratesandproteinadsorptionandforcellattachmentToensurethattheporestructureissuitable,differentmethodsareusedtodeterminethemacro/nanostructureofthescaffold•Scanningelectronmicroscope(SEM)•X-raymicrotomography(µCT)•Transmissionelectronmicroscope(TEM)Traditionally,mercuryintrusionporosimetry(MIP)coupledtogetherwithWashburnequationisusedtodeterminetheporesizedistributionVolumeofmercurythatintrudesintothesamplematerialwitheachpressurechangethevolumeofporesinthecorrespondingsizeclass•Volumeofmercurythatentersporesismeasuredbyamercurypenetrometer(anelectricalcapacitancedilatometer)MIPisdestructivetothescaffoldduetomercurycontaminationTheuserisalsounabletodeterminewhethertheporesizemeasuredisthetrueinterconnectingdiameterPL=pressureofliquidPG=pressureofga