title: Fluxgate magnetorelaxometry: a new approach to study the release properties of hydrogel cylinders and microspheres.
abstract: Hydrogels are under investigation as long term delivery systems for biomacromolecules as active pharmaceutical ingredients. The release behavior of hydrogels can be tailored during the fabrication process. This study investigates the applicability of fluxgate magnetorelaxometry (MRX) as a tool to characterize the release properties of such long term drug delivery depots. MRX is based on the use of superparamagnetic core-shell nanoparticles as model substances. The feasibility of using superparamagnetic nanoparticles to study the degradation of and the associated release from hydrogel cylinders and hydrogel microspheres was a major point of interest. Gels prepared from two types of photo crosslinkable polymers based on modified hydroxyethylstarch, specifically hydroxyethyl starch-hydroxyethyl methacrylate (HES-HEMA) and hydroxyethyl starch-polyethylene glycol methacrylate (HES-P(EG)(6)MA), were analyzed. MRX analysis of the incorporated nanoparticles allowed to evaluate the influence of different crosslinking conditions during hydrogel production as well as to follow the increase in nanoparticle mobility as a result of hydrogel degradation during release studies. Conventional release studies with fluorescent markers (half-change method) were performed for comparison. MRX with superparamagnetic nanoparticles as model substances is a promising method to analyze pharmaceutically relevant processes such as the degradation of hydrogel drug carrier systems. In contrast to conventional release experiments MRX allows measurements in closed vials (reducing loss of sample and sampling errors), in opaque media and at low magnetic nanoparticle concentrations. Magnetic markers possess a better long-term stability than fluorescent ones and are thus also promising for the use in in vivo studies.
authors: Technische Universität Braunschweig, Institut für Pharmazeutische Technologie, Mendelssohnstr. 1, 38106 Braunschweig, Germany.
authors: S
authors: S
authors: Wöhl-Bruhn
authors: E
authors: E
authors: Heim
authors: A
authors: A
authors: Schwoerer
authors: A
authors: A
authors: Bertz
authors: S
authors: S
authors: Harling
authors: H
authors: H
authors: Menzel
authors: M
authors: M
authors: Schilling
authors: F
authors: F
authors: Ludwig
authors: H
authors: H
authors: Bunjes
mesh_terms: D016503:Drug Delivery Systems; D006170:Gum Arabic / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry*; D006895:Hydroxyethyl Starch Derivatives / Q000737:chemistry; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008689:Methacrylates / Q000737:chemistry; D008863:Microspheres; D011092:Polyethylene Glycols / Q000737:chemistry; D013678:Technology, Pharmaceutical
chemical_list: D020100:Hydrogels; D006895:Hydroxyethyl Starch Derivatives; D058185:Magnetite Nanoparticles; D008689:Methacrylates; C524499:polyethylene glycol methacrylate; D011092:Polyethylene Glycols; C005044:hydroxyethyl methacrylate; D006170:Gum Arabic