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Synthesis and characterization of grafted thermosensitive hydrogels for heating activated controlled release.

Abstract

Poly(N-isopropylacrylamide), PNIPAAm, hydrogels are negatively thermosensitive which means that they have an expanded hydrogel structure at low temperatures and a shrunken structure at high temperatures. Based on this negative thermosensitivity of PNIPAAm, a drug delivery system with PNIPAAm oligomers grafted onto poly(hydroxyethyl methacrylate) PHEMA, a thermally nonresponsive polymer was designed. Poly(hydroxyethyl methacrylate-g-N-isopropylacrylamide), P(HEMA-g-NIPAAm) hydrogels were synthesized to control the release of an imbedded drug. This new grafted system exhibited high diffusivity at temperatures greater than the lower critical solution temperature (LCST) of the PNIPAAm oligomers. Utilizing PNIPAAm's LCST of approximately 34 degrees C, the release rate was controlled by the temperature of the release medium. The LCST of PNIPAAm was tuned by making copolymers with hydrophobic butyl methacrylate (BMA). Theophylline and inulin release profiles were studied using PHEMA, PNIPAAm and P(HEMA-g-NIPAAm) at three temperatures with drug diffusion coefficients determined as a function of temperature and drug type. The molecular weights between crosslinks and mesh sizes of PHEMA hydrogels were calculated using Flory-Rehner and rubber-elasticity theories.

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  • Publisher Full Text
  • Authors

    ,

    Source

    International journal of pharmaceutics 336:2 2007 May 24 pg 241-7

    MeSH

    Acrylic Resins
    Calorimetry, Differential Scanning
    Cross-Linking Reagents
    Delayed-Action Preparations
    Diffusion
    Drug Delivery Systems
    Hot Temperature
    Hydrogels
    Inulin
    Kinetics
    Methacrylates
    Molecular Weight
    Polyhydroxyethyl Methacrylate
    Polymers
    Temperature
    Theophylline

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    17234371

    Citation

    TY - JOUR T1 - Synthesis and characterization of grafted thermosensitive hydrogels for heating activated controlled release. AU - Ankareddi,Induvadana, AU - Brazel,Christopher S, Y1 - 2006/12/03/ PY - 2006/10/10/received PY - 2006/11/20/revised PY - 2006/11/27/accepted PY - 2006/12/3/aheadofprint PY - 2007/1/20/pubmed PY - 2007/8/19/medline PY - 2007/1/20/entrez SP - 241 EP - 7 JF - International journal of pharmaceutics JO - Int J Pharm VL - 336 IS - 2 N2 - Poly(N-isopropylacrylamide), PNIPAAm, hydrogels are negatively thermosensitive which means that they have an expanded hydrogel structure at low temperatures and a shrunken structure at high temperatures. Based on this negative thermosensitivity of PNIPAAm, a drug delivery system with PNIPAAm oligomers grafted onto poly(hydroxyethyl methacrylate) PHEMA, a thermally nonresponsive polymer was designed. Poly(hydroxyethyl methacrylate-g-N-isopropylacrylamide), P(HEMA-g-NIPAAm) hydrogels were synthesized to control the release of an imbedded drug. This new grafted system exhibited high diffusivity at temperatures greater than the lower critical solution temperature (LCST) of the PNIPAAm oligomers. Utilizing PNIPAAm's LCST of approximately 34 degrees C, the release rate was controlled by the temperature of the release medium. The LCST of PNIPAAm was tuned by making copolymers with hydrophobic butyl methacrylate (BMA). Theophylline and inulin release profiles were studied using PHEMA, PNIPAAm and P(HEMA-g-NIPAAm) at three temperatures with drug diffusion coefficients determined as a function of temperature and drug type. The molecular weights between crosslinks and mesh sizes of PHEMA hydrogels were calculated using Flory-Rehner and rubber-elasticity theories. SN - 0378-5173 UR - https://www.unboundmedicine.com/medline/citation/17234371/Synthesis_and_characterization_of_grafted_thermosensitive_hydrogels_for_heating_activated_controlled_release_ L2 - http://linkinghub.elsevier.com/retrieve/pii/S0378-5173(06)01038-6 ER -