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Interaction between lysozyme and poly(acrylic acid) 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.ORCID iD: 0000-0002-0895-1180
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
2007 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 316, no 2, 350-359 p.Article in journal (Refereed) Published
Abstract [en]

The interaction between lysozyme and oppositely charged poly(acrylic acid) microgels was investigated by micromanipulator-assisted light microscopy, confocal microscopy and circular dichroism. Lysozyme uptake and distribution within the microgel particles, and its effect on microgel deswelling, was studied regarding effects of pH, ionic strength and lysozyme concentration. For a range of conditions, lysozyme distributes nonuniformly within the microgels, forming a lysozyme/microgel shell in the outer parts of the microgel. This shell formation is associated both with increased lysozyme loading to the microgels and with increased lysozyme-induced microgel deswelling. At high microgel charge density, the shell formation displays nonmonotonic ionic strength dependence. The shells formed are characterized by a net positive charge, and by relatively fast exchange of lysozyme between shell and solution, although the exchange kinetics decreases strongly with decreasing ionic strength. At conditions of slower exchange kinetics, the shells are characterized by an effective pore size of less than about 4 nm.

Place, publisher, year, edition, pages
2007. Vol. 316, no 2, 350-359 p.
Keyword [en]
confocal, microscopy, lysozyme, microgel, poly(acrylic acid), surface phase, phase separation
National Category
Pharmaceutical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-15621DOI: 10.1016/j.jcis.2007.07.052ISI: 000250987500017PubMedID: 17719601OAI: oai:DiVA.org:uu-15621DiVA: diva2:43392
Available from: 2008-02-25 Created: 2008-02-25 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Interaction Between Microgels and Oppositely Charged Proteins
Open this publication in new window or tab >>Interaction Between Microgels and Oppositely Charged Proteins
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis reports on interactions between microgels and oppositely charged proteins. Two types of negatively charged microgels are investigated: poly(acrylic acid) microgels of 60-80 µm in diameter, and colloidal poly(NIPAM-co-acrylic acid) microgels of around 1 µm in diameter. The proteins used are lysozyme and cytochrome c, which both have positive net charge. The experimental techniques used in the studies of the larger microgels are mainly micromanipulator-assisted microscopy and confocal microscopy, while the smaller microgels are studied mainly with dynamic light scattering.

It is observed that large amounts of protein are absorbed by the microgels, and that the uptake involves a substantial deswelling of the microgel. The uptake generally decreases as the ionic strength is increased, which is characteristic of electrostatic interactions. An ionic strength optimum is however observed in the case of lysozyme and poly(acrylic acid) microgels, where the highest uptake (10 gram lysozyme / gram microgel) is observed at ionic strength 40 mM. Cytochrome c uptake in poly(acrylic acid) microgels results in homogenous cytochrome c distribution throughout the microgel, whereas lysozyme uptake results in core-shell formation; the lysozyme concentration becomes much higher in the shell (outer part of the microgel) than in the core (inner part of the microgel). The shell constitutes a stress-bearing network which is sufficiently porous to allow protein diffusion through the shell. The different protein distributions are associated with different protein-protein interactions; strong protein-protein attraction promotes shell formation.

In the case of colloidal microgels, lysozyme uptake decreases the electrophoretic mobility and the colloidal stability of the microgels. The microgels flocculate as the uptake reaches charge ratio 0.6-0.7 (positive lysozyme charges/negative microgel charges), largely independent of ionic strength. Initial experiments on the combination of cytochrome c and colloidal microgels show that colloidal stability is maintained at a range of conditions (ionic strength, protein concentration) where flocculation occurred in the case of lysozyme.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 71 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 98
Series
Keyword
microgel, protein, uptake, distribution, core-shell, colloidal stability
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-101246 (URN)978-91-554-7526-0 (ISBN)
Public defence
2009-06-05, B21, BMC, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2009-05-15 Created: 2009-04-21 Last updated: 2009-05-15Bibliographically approved

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Johansson, ChristianHansson, PerMalmsten, Martin

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