Growth and accelerated differentiation of mesenchymal stem c(3)

PaperJournalofMaterialsChemistryB

withtheconcentrationof10mMwereemployedforadsorptionkineticswiththeadditionofthesubstrates.TheadsorptionofthechemicalswasevaluatedwithUV-Visspectroscopy.Theamountoftheadsorbedwasdeterminedfromthechangeinabsorptionbeforeandaertheadsorption.

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manifestedtheabsorptionpeaksat240nm,and310nm.TheyarecharacteristicabsorptionofGOfromthep–p*transitionsofaromaticC–Cbondsandn–p*transitionsofC]Obonds,respectively.TheseresultsconrmedthesuccessfulformationoftheGO/PLLcompositelm.3.2

MSCsviabilityandproliferationontheGO/PLLlm

3Resultsanddiscussion

3.1

FabricationandcharacterizationofGOandGO/PLLlmGOcanbeobtainedbychemicaloxidationandexfoliationofgraphite.TheproducedGOwasconrmedrstbytheatomicforcemicroscopy(AFM)technique.ItwasfoundthattheGOTodeterminewhetherornottheGO/PLLlmhadasignicante ectontheMSCs,uorescencestainingwasperformedusingcalcein-AM(tostainlivecellswithgreencolor)andethidiumhomodimer(tostaindeadcellswithredcolor).FluorescencemicroscopyrevealedthatmostoftheMSCsplatedonthesheetshadlateraldimensionsofonetoseveralhundrednanometerswithathicknessof1.0nmapproximately(Fig.S1 ),whichischaracteristicofthefullyexfoliatedGOsheets.28ThentheFTIRspectrumwasusedtocharacterizetheproducedGO.InFig.S2, theGOspectrumshowedthepresenceofO–H(3430cmÀ1),C]O(1733cmÀ1),C]C(1630cmÀ1),andC–O(1128cmÀ1).29Asacontrast,besidesthesesites,theIRspectrumoftheLbL-assembled(GO/PLL)4compositelmexhibitedPLLabsorptionfeatures,suchasN–H(3259cmÀ1),C]O(1633cmÀ1)andC–N(1552cmÀ1).Also,thenanotopographyandthicknessofthe(GO/PLL)4lmweredeterminedbyAFM.Fig.2AshowsclearlytheexistenceofGOsheetsonthelmsurfaceshowingthethicknessofthe(GO/PLL)4lmof5.51nm(Fig.S3 ).ThebuildupoftheGO/PLLlmswasfurthermoni-toredbyUV-Visspectroscopy(Fig.2B).ComparingwiththeUV-VisspectrumofPLL,allthespectraoftheGO/PLLlms

Fig.2

(A)AFMimageofthe(GO/PLL)4 lm;(B)1,2,UV-Vis3,

4.absorption

spectraofGO,PLLandthe(GO/PLL)n lm,n¼Thisjournalis©TheRoyalSocietyofChemistry2014compositelmswerealive,asshowninFig.3A.Fromthephasecontrastimage(Fig.3B),thecellsdisplayedthepolygonalandattenedcellmorphologyontheGO/PLLlmandpresentedtheelongatedstructurewiththeirspindleshape.ThemorphologyofcellsontheotherstudiedsurfacesisshowninFig.S4. Additionally,acellcountkit-8(CCK-8)assaywascarriedouttoconrmthecellviabilitydataaer1dayand7dayofcellcultureonthecompositelmrespectively.Glasscoverslips(treatedwithpiranhasolution),GO-coatedcoverslips(GO-coverslips)fabricatedwiththespincoatingtechnique,PLLcoatedglasscoverslips(PLL-coverslips)andtissueculturepolystyrene(TCPS)wereemployedforcomparison.AsshowninFig.

3C,

Fig.3

(A)FluorescenceimagesofMSCswereobtainedonthe(GO/

PLL)4 lmbylive/deadstainingofcellsafterincubationfor3days.Livecellswerestained uorescencegreen,anddeadcellsappearedred.(B)PhasecontrastimagesofMSCsculturedfor3daysonthe(GO/PLL)4 lminnormalcellculturemedia.(C)CellviabilitiesofMSCsculturedonallthestudiedsurfacesincellculturemediabyday1andday7.(D)Cellproliferationonallthestudiedsurfacesasestimatedbytheratio(D7/D1).(E)GrowthkineticsofcellsontheTCPSandGO/PLLcomposite lms.(F)Thepopulationdoublingtimesofcellsonallthestudiedsurfaces.Thetotalnumberofcellswasdeterminedatdi erenttimepointstoobtainthedoublingtime.J.Mater.Chem.B,2014,2,5461–5467|5463

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