title: Chain and pore-blocking effects on matrix degradation in protein-loaded microgels.
abstract: Factors affecting matrix degradation in protein-loaded microgels were investigated for dextran-based microgels, the sugar-binding protein Concanavalin A (ConA), and the dextran-degrading enzyme Dextranase. For this system, effects of enzyme, protein, and glucose concentrations, as well as pH, were considered. Microgel network degradation was monitored by micromanipulator-assisted light microscopy, whereas enzyme and protein distributions were monitored by confocal microscopy. Results show that Dextranase-mediated microgel degradation increased with increasing enzyme concentration, whereas an increased ConA loading in the dextran microgels caused a concentration-dependent decrease in microgel degradation. In the presence of glucose, competitive release of microgel-bound ConA restored the microgel degradation observed in the absence of ConA. To clarify effects of mass transport limitations, microgel degradation was compared to that of non-cross-linked dextran, demonstrating that ConA limits enzyme substrate access in dextran microgels primarily through pore blocking and induction of pore shrinkage. The experimentally observed effects were qualitatively captured by a modified Michaelis-Menten approach for spherical symmetry, in which network blocking by ConA was included. Taken together, the results demonstrate that matrix degradation of protein-loaded microgels depends sensitively on a number of factors, which need to be considered in the use of microgels in biomedical applications.
authors.affiliation: Department of Pharmacy, Uppsala University , P.O. Box 580, SE-751 23 Uppsala, Sweden.
authors.forename: Ronja
authors.initials: R
authors.lastname: Widenbring
authors.forename: Göran
authors.initials: G
authors.lastname: Frenning
authors.forename: Martin
authors.initials: M
authors.lastname: Malmsten
mesh_terms: D003208:Concanavalin A / Q000737:chemistry*; D003910:Dextranase / Q000737:chemistry; D003911:Dextrans / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D018613:Microscopy, Confocal / Q000379:methods
chemical_list: D003911:Dextrans; D005782:Gels; D003208:Concanavalin A; D003910:Dextranase; D005947:Glucose