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Chain and Pore-Blocking Effects on Matrix Degradation in Protein-Loaded Microgels
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
2014 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 10, 3671-3678 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2014. Vol. 15, no 10, 3671-3678 p.
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:uu:diva-236549DOI: 10.1021/bm5009525ISI: 000343026600022PubMedID: 25144139OAI: oai:DiVA.org:uu-236549DiVA: diva2:766101
Available from: 2014-11-26 Created: 2014-11-19 Last updated: 2015-03-11Bibliographically approved
In thesis
1. Microgel Interactions with Peptides and Proteins: Consequence of Peptide and Microgel Properties
Open this publication in new window or tab >>Microgel Interactions with Peptides and Proteins: Consequence of Peptide and Microgel Properties
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microgels are lightly cross-linked hydrogel particles in the sub-micrometer to micrometer size range with a capacity to drastically change their volume in response to changes in the external environment. Microgels have an ability to bind and store substances such as biomacromolecular drugs, notably proteins and peptides, and release them upon stimuli, making them potential candidates as drug delivery vehicles and functional biomaterials. This thesis aims at clarifying important factors affecting peptide-microgel interactions. These interactions were studied by micromanipulator-assisted light and fluorescence microscopy focusing on microgel deswelling in response to peptide binding, as well as re-swelling in response to peptide release or enzymatic degradation. To evaluate peptide uptake in microgels, solution depletion measurements were used whereas the peptide secondary structure was investigated by circular dichroism. In addition, the peptide and enzyme distribution within microgels was analyzed with confocal microscopy.

Results presented in this thesis demonstrate that peptide incorporation into microgels, as well as peptide-induced microgel deswelling, increases with peptide length and charge density. In addition, results demonstrate that the peptide charge (length) rather than peptide charge density determines microgels deswelling. End-to-end cyclization is shown to not noticeably influence peptide-microgel interactions, suggesting that peptide cyclization can be used in combination with oppositely charged microgel carriers to improve the proteolytic and chemical stability of the peptide compared to the corresponding linear variant. Peptide secondary structure is found to drastically affect peptide incorporation into, and release from, oppositely charged microgels. Furthermore, it is shown that microgel charge density, peptide molecular weight, and enzyme concentration all greatly influence microgel bound peptide degradation. Of importance for applications, protective effects of microgels against proteolytic peptide degradation are observed only at sufficiently high microgel charge densities. Enzyme-mediated microgel degradation is shown to increase with increasing enzyme concentration, while an increased peptide loading in microgels causes a concentration-dependent decrease in microgel degradation.

Taken together, results obtained in this work have provided some insight into factors of importance for rational use of microgels as delivery systems for protein or peptide drugs, but also in a host of other biomedical applications using weakly cross-linked polymer systems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 65 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 196
Binding, Degradation, Enzyme, Gel, Hydrogel, Microgel, Peptide, Protein, Release
National Category
Pharmaceutical Sciences Physical Chemistry Materials Engineering
Research subject
Pharmaceutical Physical Chemistry
urn:nbn:se:uu:diva-242893 (URN)978-91-554-9157-4 (ISBN)
Public defence
2015-03-20, B21, BMC, Husargatan 3, Uppsala, 09:15 (English)
Available from: 2015-02-24 Created: 2015-02-02 Last updated: 2015-03-11

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Widenbring, RonjaFrenning, GöranMalmsten, Martin
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