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Protein Interactions with Bottle-Brush Polymer Layers: Effect of Side Chain and Charge Density Ratio Probed by QCM-D and AFM
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
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2010 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 349, no 1, 265-274 p.Article in journal (Refereed) Published
Abstract [en]

Silica surfaces were coated with a range of cationic bottle-brush polymers with 45 units long poly(ethylene oxide) side chains, and their efficiency in reducing protein adsorption was probed by QCM-D, reflectometry and AFM. Preadsorbed layers formed by bottle-brush polymers with different side chain to charge ratio was exposed to two proteins with different net charge, lysozyme and BSA. The reduction in protein adsorption was found to depend on both the type of protein and on the nature of the polyelectrolyte layer. The most pronounced reduction in protein adsorption was achieved when the fraction of charged backbone segments was in the range 0.25-0.5 equivalent to a fraction of poly(ethylene oxide) side chains of 0.75-0.5. It was concluded that these polymers have enough electrostatic attachment points to ensure a strong binding to the surface, and at the same time a sufficient amount of poly(ethylene oxide) side chains to counteract protein adsorption. In contrast, a layer formed by a highly charged polyelectrolyte without side chains was unable to resists protein adsorption. On such a layer the adsorption of negatively charged BSA was strongly enhanced, and positively charged lysozyme adsorbed to a similar extent as to bare silica. AFM colloidal probe force measurement between silica surfaces with preadsorbed layers of bottle-brush polymers were conducted before and after exposure to BSA and lysozyme to gain insight into how proteins were incorporated in the bottle-brush polymer layers.

Place, publisher, year, edition, pages
2010. Vol. 349, no 1, 265-274 p.
Keyword [en]
Protein repellency, Protein adsorption, Surface forces, AFM, QCM-D, Reflectometry, BSA, Lysozyme, Bottle-brush polymer
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-14003DOI: 10.1016/j.jcis.2010.05.061ISI: 000279966700036Scopus ID: 2-s2.0-77954175021OAI: oai:DiVA.org:kth-14003DiVA: diva2:329004
Funder
Swedish Research Council
Note
QC 20100707 Uppdaterad från submitted till published (20110204).Available from: 2010-07-07 Created: 2010-07-07 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Adsorption behaviour of bottle-brush and block copolymers at solid-liquid interfaces
Open this publication in new window or tab >>Adsorption behaviour of bottle-brush and block copolymers at solid-liquid interfaces
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis was spurred on by needs of current scientific and technological developments in the area of surface modification by use of adsorbed polymer layers. The importance of surface properties of polymer layers can be imparted in a broad spectrum of interfacial-related applications like lubrication, colloidal stability, detergency, and protein resistant surfaces, to just mention a few. Irrespective of all areas of application an underlying factor in all is the deep implication and footprint the molecular architecture has on the interfacial properties of polymer layers. In this context this thesis has the intention of raising awareness of the importance of the polymer architecture on interfacial behavior and the stability of layers formed by bottle-brush polymers and by temperature responsive block copolymers under different conditions. The first part of this thesis work was largely devoted to the surface properties of a series of cationic bottle-brush polymers, consisting of a main chain carrying charges and poly(ethylene oxide) (PEO) side chains close to randomly distributed along the backbone. Here particular attention was devoted to varying the molecular architecture by changing the charge/PEO ratio along the backbone. The studies demonstrated that the surface excess of the polymers went through a maximum as the number of backbone charges increased. Furthermore, the bottle-brush adlayers revealed sensitivity to changes in both ionic strength and pH when the numbers of backbone charges were relatively low. Layer properties were comprehensively elucidated by determining not only the adsorbed mass, but also layer thickness, water content and layer viscoelasticity. The change in these properties during formation of the adsorption layer was found to be complex, demonstrating significant conformational changes in the layer. The studies aimed at creating surface coatings with good resistance against species of high surface affinity, with a central interest in proteins, elucidated the optimal balance of the bottle-brush structure. The results revealed two scenarios, depending on both the type of protein and the areal density (grafting density) of the PEO side chains at the silica surface, where either protein adsorption was suppressed or enhanced by the presence of adlayers of the bottle-brush polymers. Low protein adsorption was achieved when the polymers have enough electrostatic attachment points to ensure a strong binding to the surface and at the same time a sufficient amount of PEO side chains that screen the protein-surface interactions. In the second part of the thesis a combination of QCM-D, AFM and reflectometry techniques was employed to probe the interfacial characteristics of temperature responsive cationic diblock copolymers, poly(N-ivisopropylacrylamide)m-block-poly(3-acrylamidopropyl)trimethyl ammonium chloride)n. The adsorption of these polymers to silica was of a high affinity, with no dramatic structural changes occurring during the layer build-up. The temperature dependent behavior of the adlayers demonstrated that the polymer interfacial conformation could be reversibly altered merely by cycling temperature above and below the lower critical solution temperature (LCST). This was found to have significant effects on both surface forces and boundary lubrication.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xiii, 77 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:22
Keyword
Adsorption, Lubrication, Layer viscoelasticity, Protein repellency, Polymer architecture, Silica, Bottle-brush polymers, Poly(ethylene oxide), PEO, Block copolymer, Poly(N-isopropylacrylamide), QCM-D, AFM, Reflectometry
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-13213 (URN)978-91-7415-611-4 (ISBN)
Public defence
2010-06-14, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100707Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2011-02-04Bibliographically approved

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