Prime

Type your tag names separated by a space and hit enter

Poly(N-isopropylacrylamide-co-acrylamide) cross-linked thermoresponsive microspheres obtained from preformed polymers: Influence of the physico-chemical characteristics of drugs on their release profiles.

Abstract

Poly(N-isopropylacrylamide-co-acrylamide) copolymer was synthesized as an interesting thermoresponsive material possessing a phase transition temperature of around 36 degrees C in phosphate buffer, pH 7.4 (PB); the concentration was 10%, w/v. The copolymer maintains a sharp phase transition at a relatively high percentage of acrylamide. The lower critical solution temperature (LCST) of the copolymer is influenced by the concentration of copolymer solution in PB. The copolymer was transformed in thermoresponsive microspheres by chemical cross-linking of amide groups with glutaraldehyde. The key factors for the successful preparation of microspheres are the use of a concentrated polymer solution, a temperature (38 degrees C) that is high enough but lower than LCST, and a long reaction time (48h). The microspheres were characterized by optical and scanning electron microscopy, swelling/deswelling kinetics, swelling degree, and PB retention at different temperatures. Finally, the influence of hydrophilicity/hydrophobicity and the molecular weight of the drugs (propranolol, lidocaine, vitamin B(12)) on their release profile from thermoresponsive microspheres were examined. Above LCST the hydrogel matrix is in the dehydrated state and hydrophobic interactions between the hydrophobic drugs and the polymer occur, modulating the release rate of the drugs. For hydrophilic drugs, the release rate is modulated mainly by the steric interaction between the drug molecule and the matrix.

Links

  • Publisher Full Text
  • Authors+Show Affiliations

    ,

    Department of Pharmaceutical Sciences, University of Ferrara, I-44100 Ferrara, Italy. ghefun@icmpp.ro

    ,

    Source

    Acta biomaterialia 5:1 2009 Jan pg 363-73

    MeSH

    Acrylic Resins
    Biocompatible Materials
    Buffers
    Cross-Linking Reagents
    Drug Delivery Systems
    Hydrogen-Ion Concentration
    Kinetics
    Magnetic Resonance Spectroscopy
    Microscopy, Electron, Scanning
    Microspheres
    Phosphates
    Polymers
    Spectroscopy, Fourier Transform Infrared
    Temperature

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    18723416