title: Hydroxyethyl starch-based polymers for the controlled release of biomacromolecules from hydrogel microspheres.
abstract: Hydrogels are promising delivery systems for the controlled release of biomacromolecules. Based on previous studies, hydrogels were prepared from crosslinkable hydroxyethyl starch with new linker groups to improve mechanical and release properties of the resulting hydrogels. Polyethylene glycol methacrylate with two different spacer lengths was used to obtain polymers (HES-P(EG)(n)MA) with increased hydrophilicity and degradability, whereas a polymer with methacrylate linker directly at the starch backbone (HES-MA) resulted in a less degradable polymer. Hydrogel disks were obtained by UV crosslinking and characterized by swelling and rheological measurements. The hydrogel strength was strongly influenced by the polymer concentration. Using a water-in-water emulsion process, hydrogel microspheres were prepared. The influence of the type of the linker, the degree of substitution and the phase ratio in the production process on the properties of the microspheres was investigated. Depending on the preparation parameters, particles with narrow particle size distribution and encapsulation efficiencies of up to more than 80% for FITC-dextran 70 kDa (FD70) were obtained. Incorporated FITC-labeled IgG showed a faster release from hydrogel microspheres than FD70. The release rate of incorporated FD70 could be adjusted by using different polymers (HES-P(EG)(10)MA>HES-P(EG)(6)MA>HES-MA).
authors.affiliation: Institute of Pharmaceutical Technology, Technische Universität Braunschweig, Braunschweig, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Wöhl-Bruhn
authors.forename: Andreas
authors.initials: A
authors.lastname: Bertz
authors.forename: Steffen
authors.initials: S
authors.lastname: Harling
authors.forename: Henning
authors.initials: H
authors.lastname: Menzel
authors.forename: Heike
authors.initials: H
authors.lastname: Bunjes
mesh_terms: D003692:Delayed-Action Preparations; D003911:Dextrans / Q000008:administration & dosage; D004337:Drug Carriers / Q000737:chemistry; D016503:Drug Delivery Systems; D004655:Emulsions; D016650:Fluorescein-5-isothiocyanate / Q000008:administration & dosage / Q000031:analogs & derivatives; D020100:Hydrogels; D057927:Hydrophobic and Hydrophilic Interactions; D006895:Hydroxyethyl Starch Derivatives / Q000737:chemistry*; D007074:Immunoglobulin G / Q000008:administration & dosage; D008689:Methacrylates / Q000737:chemistry*; D008863:Microspheres; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D012212:Rheology
chemical_list: D003692:Delayed-Action Preparations; D003911:Dextrans; D004337:Drug Carriers; D004655:Emulsions; D020100:Hydrogels; D006895:Hydroxyethyl Starch Derivatives; D007074:Immunoglobulin G; D008689:Methacrylates; C015219:fluorescein isothiocyanate dextran; C524499:polyethylene glycol methacrylate; D011092:Polyethylene Glycols; D016650:Fluorescein-5-isothiocyanate