title: Layer-by-layer coating of degradable microgels for pulsed drug delivery.
abstract: Recently, we reported on "self-rupturing" microcapsules which consist of a biodegradable dextran-based microgel surrounded by a polyelectrolyte membrane. Degradation of the microgel increases the swelling pressure in the microcapsules which, when sufficiently high, ruptures the surrounding polyelectrolyte membrane. The membrane surrounding the microgels is deposited using the layer-by-layer (LbL) technique, which is based on the alternate adsorption of oppositely charged polyelectrolytes onto a charged substrate. In this paper, we characterize with confocal microscopy, electrophoretic mobility, scanning electron microscopy and atomic force microscopy in detail the deposition and the properties of the LbL coatings on the dextran microgels. We show that by fine-tuning the properties of both the microgel core and the LbL membrane the swelling pressure which is evoked by the degradation of the microgel is indeed able to rupture the surrounding LbL membrane. Further, we show that the application of an LbL coating on the surface of the microgels dramatically lowers the burst release from the microcapsules and results in massive release at the time the microcapsules rupture.
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium.
authors.forename: B G
authors.initials: BG
authors.lastname: De Geest
authors.forename: C
authors.initials: C
authors.lastname: Déjugnat
authors.forename: E
authors.initials: E
authors.lastname: Verhoeven
authors.forename: G B
authors.initials: GB
authors.lastname: Sukhorukov
authors.forename: A M
authors.initials: AM
authors.lastname: Jonas
authors.forename: J
authors.initials: J
authors.lastname: Plain
authors.forename: J
authors.initials: J
authors.lastname: Demeester
authors.forename: S C
authors.initials: SC
authors.lastname: De Smedt
mesh_terms: D003692:Delayed-Action Preparations; D003911:Dextrans / Q000138:chemical synthesis / Q000737:chemistry*; D004337:Drug Carriers; D004339:Drug Compounding; D004586:Electrophoresis; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D020100:Hydrogels; D006863:Hydrogen-Ion Concentration; D008689:Methacrylates / Q000138:chemical synthesis / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D010539:Permeability; D011073:Polyamines / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry*; D012235:Rhodamines / Q000737:chemistry; D012995:Solubility; D013499:Surface Properties; D013678:Technology, Pharmaceutical; D013997:Time Factors
chemical_list: D003692:Delayed-Action Preparations; D003911:Dextrans; D004337:Drug Carriers; D005456:Fluorescent Dyes; D020100:Hydrogels; D008689:Methacrylates; D011073:Polyamines; D011137:Polystyrenes; D012235:Rhodamines; C508284:dextran hydroxyethyl methacrylate; C015219:fluorescein isothiocyanate dextran; C063994:polyallylamine; C009434:tetramethylrhodamine isothiocyanate; C003321:polystyrene sulfonic acid; D016650:Fluorescein-5-isothiocyanate