title: Controlled drug delivery systems based on thiolated chitosan microspheres.
abstract: The aim of the present study was to verify the potential of chitosan-thio-butyl-amidine (TBA) microspheres as carrier systems for controlled drug delivery. In this study microspheres were prepared utilizing water in oil (w/o) emulsification solvent evaporation technique. A concentration of 0.5% of chitosan-TBA conjugate displaying 100 microM thiol groups per gram polymer was used in the aqueous phase of the emulsion in order to prepare microspheres. The obtained non-aggregated free-flowing microspheres were examined with conventional light microscope as well as scanning electron microscopy (SEM). The microscopic images indicated that the prepared chitosan-TBA microspheres were of spherical shape and smooth surface while microparticles obtained from the unmodified chitosan were of porous structure and non-spherical shape. Particle size distribution was determined to be in the range from 1 to 59 microm. The free thiol group content of chitosan-TBA microspheres prepared with an aqueous phase of pH 2, 5, and 6.5 were determined to be 71.4, 49.4, and 8.2 microM/g polymer, respectively. Furthermore, results attained from in vitro release studies with fluorescein isothiocyanate labelled dextran (FITC-dextran) loaded chitosan-TBA microspheres showed a controlled release rate for more than three hours while the control reached the maximum peak level of release already within an hour. According to these results, chitosan-TBA microspheres seem to be a promising tool in transmucosal drug delivery for poorly absorbed therapeutic agents.
authors.affiliation: Institute of Pharmaceutical Technology and Biopharmaceutics, Center of Pharmacy, University of Vienna, Austria. andreas.bernkop@uibk.ac.at
authors.forename: M
authors.initials: M
authors.lastname: Elhassan Imam
authors.forename: Andreas
authors.initials: A
authors.lastname: Bernkop-Schnürch
mesh_terms: D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000737:chemistry* / Q000493:pharmacokinetics; D003911:Dextrans / Q000737:chemistry / Q000493:pharmacokinetics; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D010316:Particle Size; D013678:Technology, Pharmaceutical / Q000379:methods
chemical_list: D003692:Delayed-Action Preparations; D003911:Dextrans; C493042:chitosan-4-thiobutylamidine; D002686:Chitin; D016650:Fluorescein-5-isothiocyanate