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@ARTICLE{Ghugare:11790,
      author       = {Ghugare, S.V. and Chiessi, E. and Telling, M.T.F. and
                      Deriu, A. and Gerelli, Y. and Wuttke, J. and Paradossi, G.},
      title        = {{S}tructure and {D}ynamics of a {T}hermoresponsive
                      {M}icrogel around {I}ts {V}olume {P}hase {T}ransition
                      {T}emperature},
      journal      = {The journal of physical chemistry / B},
      volume       = {114},
      issn         = {1520-6106},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {PreJuSER-11790},
      pages        = {10285 - 10293},
      year         = {2010},
      note         = {This work was partially funded by MIUR-PRIN project
                      20077LCNTW. S.G. gratefully acknowledges the international
                      Ph.D. student program of the University of Rome Tor Vergata.
                      The SPHERES experiment has been supported by the European
                      Commission under the Seventh Framework Programme through the
                      Key Action: Strengthening the European Research Area,
                      Research Infrastructures, Contract no.: 226507 (NMI3). The
                      IRIS experiment was performed within Agreement No. 01/901
                      between CCLRC and CNR.},
      abstract     = {Sustained drug delivery requires the use of multifunctional
                      devices with enhanced properties. These properties include
                      responsiveness to external stimuli (such as temperature, pH,
                      ionic strength), ability to deliver suitably designed
                      ligands to specific receptors, enhanced bioadhesion to
                      cells, and cytocompatibility. Microgels represent one of
                      such multifunctional drug delivery devices. Recently, we
                      described the fabrication of a stable colloidal aqueous
                      suspension of cytocompatible microgel spheres based on a
                      poly(vinyl
                      alcohol)/poly(methacrylate-co-N-isopropylacrylamide) network
                      ( Ghugare, S. Mozetic, P. Paradossi, G. Biomacromolecules
                      2009 , 10 , 1589 ). These microgel spheres undergo an
                      entropy-driven volume phase transition around the
                      physiological temperature, this phase transition being
                      driven by the incorporation of NiPAAm residues in the
                      network. In that study, the microgel was loaded with the
                      anticancer drug doxorubicin. As the microgel shrank, a
                      marked increase in the amount of doxorubicin released was
                      noted. Indeed, dynamic light scattering measurements showed
                      the diameter reduction to be about $50\%.$ In the present
                      paper, we focus on some fundamental issues regarding
                      modifications of the hydrogel architecture at a nanoscopic
                      level as well as of the diffusive behavior of water
                      associated with the polymer network around the volume phase
                      transition temperature (VPTT). Sieving and size exclusion
                      effects were studied by laser scanning confocal microscopy
                      with the microgel exposed to fluorescent probes with
                      different molecular weights. Confocal microscopy
                      observations at room temperature and at 40 degrees C (i.e.,
                      below and above the VPTT) provided an evaluation of the
                      variation of the average pore size (from 5 nm to less than 3
                      nm). Using quasielastic neutron scattering (QENS) with the
                      IRIS spectrometer at ISIS, UK, the diffusive behavior of
                      water molecules closely associated to the polymer network
                      around the VPTT was investigated. A clear change in the
                      values of diffusion coefficient of bound water was observed
                      at the transition temperature. In addition, the local
                      dynamics of the polymer itself was probed using the QENS
                      spectrometer SPHERES at FRM II, Germany. For this study, the
                      microgel was swollen in D(2)O. An average characteristic
                      distance of about 5 A for the localized chain motions was
                      evaluated from the elastic incoherent structure factor
                      (EISF) and from the Q-dependence of the Lorentzian width.},
      keywords     = {Acrylamides: chemistry / Antibiotics, Antineoplastic:
                      chemistry / Doxorubicin: chemistry / Drug Delivery Systems /
                      Hydrogels: chemistry / Materials Testing / Molecular
                      Structure / Particle Size / Phase Transition /
                      Polymethacrylic Acids: chemistry / Polyvinyl Alcohol:
                      chemistry / Transition Temperature / Acrylamides (NLM
                      Chemicals) / Antibiotics, Antineoplastic (NLM Chemicals) /
                      Hydrogels (NLM Chemicals) / Polymethacrylic Acids (NLM
                      Chemicals) / N-isopropylacrylamide (NLM Chemicals) /
                      Doxorubicin (NLM Chemicals) / Polyvinyl Alcohol (NLM
                      Chemicals) / J (WoSType)},
      cin          = {IFF-4 / IFF-5 / Jülich Centre for Neutron Science JCNS
                      (JCNS) ; JCNS},
      ddc          = {530},
      cid          = {I:(DE-Juel1)VDB784 / I:(DE-Juel1)VDB785 /
                      I:(DE-Juel1)JCNS-20121112},
      pnm          = {BioSoft: Makromolekulare Systeme und biologische
                      Informationsverarbeitung / Großgeräte für die Forschung
                      mit Photonen, Neutronen und Ionen (PNI)},
      pid          = {G:(DE-Juel1)FUEK505 / G:(DE-Juel1)FUEK415},
      experiment   = {EXP:(DE-MLZ)SPHERES-20140101},
      shelfmark    = {Chemistry, Physical},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:20701364},
      UT           = {WOS:000280727700005},
      doi          = {10.1021/jp100962p},
      url          = {https://juser.fz-juelich.de/record/11790},
}