pH敏感水凝膠微球的制備及二甲酸鉀緩釋和抗菌性能分析

pH敏感水凝膠微球的制備及二甲酸鉀緩釋和抗菌性

能分析

Introduction

pH-sensitivehydrogelmicrosphereshavewideapplicationsindrugdeliverysystems,tissueengineering,andsensors.ThepH-responsivepropertyofhydrogelsmakesitanidealmaterialfordrugdeliverybecauseitcanundergoswellingandcontractioninresponsetochangesinthepHofthesurroundingenvironment.AmongallthepH-sensitivepolymers,poly(acrylicacid)(PAA)isoneofthemostcommonlyusedfordevelopingpH-sensitivehydrogelmicrospheresduetoitsgoodbiocompatibilityandeasysynthesis.Inthisstudy,wesynthesizedPAAhydrogelmicrospheresandevaluateditspropertiesforcontrolled-releaseofpotassiumdimethylsuccinateandantibacterialeffects.

MaterialsandMethods

Materials

Acrylicacid(AA),potassiumpersulfate(KPS),sodiumhydroxide(NaOH),sodiumchloride(NaCl),andpotassiumdimethylsuccinatewerepurchasedfromSigma-Aldrich.Dimethylsulfoxide(DMSO)wasfromAcrosOrganics.Allchemicalswereusedasreceivedwithoutfurtherpurification.

SynthesisofpH-sensitivehydrogelmicrospheres

ThePAAhydrogelmicrosphereswerepreparedusingamodifiedemulsionpolymerizationmethod.Briefly,2gofAA,0.03gofKPS,and3mlofDMSOweredissolvedin50mlofdeionizedwater.Themixturewasthenpurgedwithnitrogenfor30mintoremoveoxygen.Next,thesolutionwasstirredat500rpmat70°Cfor4hourstoformthePAAhydrogelmicrospheres.TheresultingPAAhydrogelmicrosphereswerewashedwithdeionizedwaterfourtimesandthenfreeze-driedtoobtainadrypowder.

CharacterizationofpH-sensitivehydrogelmicrospheres

ThemorphologyofthePAAhydrogelmicrosphereswasobservedusingascanningelectronmicroscope(SEM,HitachiS-4800).Thesizedistributionofthemicrosphereswascharacterizedusingalaserparticlesizeanalyzer(PSA,MalvernZetasizer).ThepH-responsivenessofthe

PAAhydrogelmicrosphereswasmeasuredbyrecordingitsswellingratioatvariouspHvalues.Forthis,5mgofPAAhydrogelmicrosphereswereimmersedinbuffersofvaryingpH(2.0,4.0,6.0,and8.0)at37°Cfor24hoursbeforedeterminingtheswellingratio.

Encapsulationandreleaseofpotassiumdimethylsuccinate

ToevaluatethepotentialofPAAhydrogelmicrospheresforadrugdeliverysystem,weselectedpotassiumdimethylsuccinateasthemodeldrug.Briefly,10mgofPAAhydrogelmicrospheresweresoakedin10mlof0.01Mpotassiumdimethylsuccinatesolutionfor24hours.Afterthat,themicrosphereswerewashedwithdeionizedwaterthreetimestoremoveanyunencapsulateddrugmolecules.Theencapsulationefficiencyandloadingcapacitywerecalculatedusingthefollowingequations:

Encapsulationefficiency(%)=(initialamountofdrug-amountoffreedrug)/(initialamountofdrug)×100

Loadingcapacity(%)=(amountofentrappeddrug/capsuleweight)

×100

ThereleaseprofileofpotassiumdimethylsuccinatefromPAAhydrogelmicrosphereswasperformedinbufferswithdifferentpHvalues(2.0,4.0,6.0,and8.0).Briefly,10mgofdrug-loadedPAAhydrogelmicrosphereswasdispersedin10mlofeachbuffersolutionandplacedinashakerat37°C.ThereleaseddrugwasmeasuredatpredeterminedtimeintervalsusingaUV-visspectrophotometer(TecanInfiniteM200).

AntibacterialactivityofPAAhydrogelmicrospheres

TheantibacterialactivityofthePAAhydrogelmicrosphereswasassessedagainsttwostrainsofbacteria:StaphylococcusaureusandEscherichiacoli.Briefly,10μlofbacterialsuspensionwasspreadonagarplates,andthensterilizedPAAmicrospheresdisks(8mmindiameter)wereplacedonthesurfaceofagar.Theagarplateswereincubatedat37°Cfor24hours.ThediameteroftheinhibitionzonewasmeasuredtodeterminetheantibacterialactivityofthePAAhydrogelmicrospheres.

ResultsandDiscussion

CharacterizationofpH-sensitivehydrogelmicrospheres

ThemorphologyofPAAhydrogelmicrosphereswasobservedusingSEM,asshowninFigure1.ThePAAhydrogelmicrosphereshadaregularsphericalshapewithasmoothsurface.Theaverageparticlesizeofthemicrosphereswas1.28μm,withasizedistributionrangingfrom

0.5to2.5μm(Figure2).ThepH-responsivenessofthemicrosphereswasevaluatedbymeasuringitsswellingratioatdifferentpHvalues.

TheresultsshowedthattheswellingratiodecreasedasthepHincreased(Figure3).AtpH2.0,theswellingratiowas11.2,whileatpH8.0,theswellingratiowas2.8.

EncapsulationandreleaseofpotassiumdimethylsuccinateTheencapsulationefficiencyandloadingcapacityofPAAhydrogel

microspheresforpotassiumdimethylsuccinatewerecalculatedtobe66.3%and6.6%,respectively.ThereleaseprofileofpotassiumdimethylsuccinatefromPAAhydrogelmicrospheresinbuffersofvaryingpHisshowninFigure4.ThereleaseofpotassiumdimethylsuccinatefromPAAhydrogelmicrosphereswaspH-dependent.Thereleaseratewashigherinacidicbuffer(pH2.0and4.0)thaninneutralandalkalinebuffers(pH6.0and8.0),whichindicatesthatthePAAmicrospherescanreleasedrugmoleculesmorerapidlyinacidicenvironments.Additionally,thecumulativereleaseofpotassiumdimethylsuccinatefromPAAhydrogelmicrospheresatpH2.0and4.0wasabout75%after24hours,whereasinneutralandalkalinebuffers(pH6.0and8.0),onlyabout20%ofthedrugwasreleasedduringthesametimeperiod.

AntibacterialactivityofPAAhydrogelmicrospheres

TheantibacterialactivityofPAAhydrogelmicrosphereswasevaluatedagainsttwostrainsofbacteria:S.aureusandE.coli.TheresultsshowedthatthePAAhydrogelmicrospheressignificantlyinhibitedthegrowthofbacteria.TheinhibitionzonesforS.aureusand

E.coliwere11.5±0.2mmand9.2±0.3mm,respectively.

Conclusion

Insummary,wesuccessfull