智能水凝胶薄膜2

pubs.acs.org/Langmuir©2009AmericanChemicalSociety

PreparationofSoftHydrogelNanoparticleswithPNIPAmHairand

CharacterizationofTheirTemperature-InducedAggregation

ShengjieLv,LianyingLiu,andWantaiYang*

StateKeyLaboratoryofChemicalResourceEngineering,CollegeofMaterialsScienceandEngineering,

BeijingUniversityofChemicalTechnology,Beijing100029,China

ReceivedJuly15,2009.RevisedManuscriptReceivedSeptember12,2009

Thereexistsagreatnumberofpublicationsconcerningthesynthesisofcore-shelland/orhairyparticlesbymeansofcontrolled/livingpolymerization.Nevertheless,howtofabricateultrafinenanosizedhairyparticles,especiallypolymericsofthairyparticles,remainsasignificantchallenge.Thispaperpresentsasimpleself-developedapproachconsistingofatwo-stepphotoinducedpolymerizationofcross-linkedpolyacrylamide(CLPAM)softhydrogelnanoparticles(5-10nmindiameter)graftedwithpoly(N-isopropylacrylamide)(PNIPAm)chains.Thearchitectureofsuchultrafinesoftwater-swollenCLPAM@PNIPAmcore/shellnanoparticles(20-35nmindiameter)demonstratedveryspecifictemperaturesensitivebehaviors.Duringheatingafastassociationprocesswasobservedatapproximately33-34°Candthesingularhairyparticleswith34nmdiametersclusteredintoaggregatesthatwere～120nmindiameter.Raisingthetemperaturefurther,however,ledtoadecreaseinsizetoabout100nmat45°C.ThisbehaviorwasattributedtotheformationofhydrophobicshelllayersaccompanyingtheshrinkageofPNIPAmchainswithchainpolartransformations.Withthecontractionpressureproducedbyfurthershrinkageofthehydrophobicshelllayers,thesoftfullyswollenPAMcoresexpelledwateranddiminishedinsize.Duringthecoolingprocess,thesecontractedcoresthatweretrappedintheaggregatesgaverisetoanearlydissociation.ThehydrophilichairyCLPAM@PNIPAmparticlesarebelievedtobepotentiallyusefulascarrierstospecifictargetregions,e.g.,cellsforcontrolleddrugdeliveryandothersmartbiomaterialapplications.

Introduction

Becauseoftheirtunablechemicalandthree-dimensional(3D)physicalstructure,decentmechanicalproperties,highwatercon-tent,andbiocompatibility,hydrogelnanoparticleshaveattractedagreatdealofinterestinmanyfields,suchastissueengineering,biomedicalimplants,drugdelivery,andbionanotechnology.1-7Awell-definedPAM-basednanoparticle,8-12asatypeofthesesoftmaterials,hasbeenwidelystudiedinbioapplications.13-15Inparticular,indrugdeliverysystems(DDS),thesmalldimensionandlargesurfaceareaofsuchnanogelscouldsignificantlyprolongtheircirculationtimeinbloodstreamsandevadetheircaptureby

*Correspondingauthor.E-mail:yangwt@mail.buct.edu.cn.Fax:(+86)10-6441-6338.

themononuclearphagocytesystem(MPS).16,17Forexample,Gaoetal.havereportedonthepreparationofultrafinehydrophilicPAm-based1-2nmnanogelsinanovelnonaqueoushexane/AOTmicroemulsion.Thesenanogelsencapsulatedwithaphoto-sensitizerwereabletoevadethereticuloendothelialsystem(RES)afterwhichtheyrenderedtheproducedsingletoxygenmoreefficientinkillinglivingtumorcells.18

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2076DOI:10.1021/la9025766PublishedonWeb10/01/2009Langmuir2010,26(3),2076–2082