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The Effect of Salt Concentration and Cation Valency on Interactions Between Mucin-Coated Hydrophobic Surfaces
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.ORCID iD: 0000-0002-5444-7276
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.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.ORCID iD: 0000-0002-2288-819X
2008 (English)In: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 134, 1-10 p.Article in journal (Refereed) Published
Abstract [en]

The AFM colloidal probe technique has been utilized in order to investigate the forces acting between preadsorbed mucin layers on uncharged, hydrophobic mercaptohexadecane-coated gold surfaces. Layers with some highly extended tails are formed when the adsorption proceeds from 25 ppm mucin solution in 30 mM NaNO3. The effects of salt concentration and cation valency on the interactions have been explored using NaCl, CaCl2, and LaCl3 in the concentration range 1–100 mM. It will be shown that the results in NaCl, where the tail length decreases as the salt concentration is increased, can be rationalized by considering the polyelectrolyte nature of mucin and the screening of intralayer electrostatic interactions between charged groups, mainly anionic sialic acid. When multivalent cations are present in solution a significant compaction of the mucin layer occurs even at low concentrations (1 mM), suggesting binding of these ions to the anionic sites of mucin. The results are discussed in relation to previous data from quartz crystal microbalance measurements on the same systems.

Place, publisher, year, edition, pages
Springer , 2008. Vol. 134, 1-10 p.
Keyword [en]
Adsorption, Atomic force microscope, Cation binding, Mucin, Multivalent ion, Surface force, Swelling, QUARTZ-CRYSTAL MICROBALANCE, ATOMIC-FORCE MICROSCOPE, SOLID-LIQUID INTERFACE, QCM-D, CHROMIUM(III) COMPLEXES, VISCOELASTIC PROPERTIES, GLYCOPROTEINS, WATER, ELLIPSOMETRY
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-13181DOI: 10.1007/2882_2008_075ISI: 000261378300001Scopus ID: 2-s2.0-54249113712ISBN: 978-3-540-68018-5 (print)OAI: oai:DiVA.org:kth-13181DiVA: diva2:321586
Conference
43rd Biennial Meeting of the German-Colloid-Society Sch Waldthausen, Mainz, GERMANY, OCT 08-10, 2007
Note

QC 20100705

Available from: 2010-06-01 Created: 2010-06-01 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Structures of Polyelectrolyte Multilayers and Preasorbed Mucin: The Influence of Counterions
Open this publication in new window or tab >>Structures of Polyelectrolyte Multilayers and Preasorbed Mucin: The Influence of Counterions
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The focus in this thesis has been to gain a fundamental understanding of how different type of salts affect preadsorbed polyelectrolytes, both natural and synthetic. The knowledge from the fundamental work is then applied on a commercial system to investigate if the efficiency can be enhanced.

We built thin films using the synthetic polyelctrolytes by using layer-by layer (LbL) deposition. The formed film is commonly known as a polyelectrolyte multilayer. The LbL method allows the incorporation of proteins, polymers, polyelectrolytes with different functions and so on within the film, thus achieving multilayers with different functions.

The major measuring technique used within this thesis is the quartz crystal microbalance with dissipation (QCM-D), which measures mass adsorbed on a surface including the trapped solvent and the viscoelastic properties of an adsorbed film. The QCM-D measurements were complemented with an optical technique, dual polarization interferometry (DPI), which measures the change in refractive index and thickness. From these parameters the dry mass and relative water content of the film can be calculated. The Atomic Force Microscopy (AFM) further gave information about forces acting between preadsorbed films.

We investigated the effect of salt on synthetic polyelectrolyte poly(allylamine hydrochloride)/poly(sodium 4-styrenesulfonate) built with the LbL technique, thus forming polyelectrolyte multilayers. We concluded that the multilayer build-up was linear and that the internal structure of the multilayer is of a compact and rigid nature. However, the type of rinsing protocol (termination of adsorption by: salt, water and salt first followed by water) has a significant effect on the outer layer of the formed multilayer. Interestingly, the structural changes only applied when poly(allylamine hydrochloride) was at the outermost layer and the most significant when water was used. We suggest that it is only the top layer that swells due to the removal of counterions resulting in increased intrachain repulsion. We further performed two-layer model calculations with the Voight model to confirm the QCM-D results as well as a novel two layer model simulation for the DPI data in order to resolve the thickness. The model calculations were in good agreement with each other thus we concluded that only the outer layer swells for this particular multilayer system.

In a related experiment we studied the adsorption of bovine submaxillary mucin (BSM), which has an important mucousal function, to different thiol modified gold surfaces as well as the effect of electrolytes (NaCl, CaCl2, LaCl3) on preadsorbed mucin to a hydrophobic thiol-modified Au surface. The salt induced an expansion at low concentrations; higher concentrations resulted in a compaction. Increasing the valence of the counter ion resultedin a compaction at low concentrations. The structural change of preadsorbed BSM was reversible for NaCl, partially reversible for CaCl2 and irreversible for LaCl3. Interestingly, the swelling of BSM could not be fully understood by using the QCM-D and thus AFM force curves of the same system were taken and the results showed that NaCl does decrease the tail length due to the effective screening of charged sites within the BSM molecule. Increasing the valence resulted in a notable compaction already at very low concentrations suggesting that the ions bind to the anionic sites on BSM.

In the last work we attempted to combine the gained knowledge from the previous studies by using the LbL-buildup on an actual commercial health care application. The above-mentioned mutlilayer were used to coat polystyrene wells in order to increase the binding of immunoglobulin (IgG). The main goal was to increase the sensitivity of the conventional enzymelinked immunosorbent spot assay (ELISpot) and subsequently the modified polystyrene wells were used with the ELISpot test with human peripheral blood mononuclear cells (PBMC) to measure the cytokine response. We suggested that the main driving force for adsorption for IgG on a PAH terminated multilayer is electrostatic attraction, whereas on PSS terminated multilayer the driving force is hydrophobic. Further, we suggested that IgG  does not overcharge the surface and the linearity of the multilayer build-up is not altered when IgG is incorporated within the multilayer structure. We concluded that the cytokine response (spots) on the built multilayers regardless thickness or adsorbed IgG is significantly less than the regular polyvinyldiene fluoride (PVDF) backed ELISpot wells. We suggested that due to the compact and rigid nature of the PAH/PSS multilayer structure it is unable to form the kind of three-dimensional antibody-binding support found in the PVDF membrane. PSS terminated PAH/PSS multilayer did not induce any cytokine response whereas PAH terminated did, which suggests that PSS totally covers the surface from the cells point of view.

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. ix, 51 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:18
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-13182 (URN)978-91-7415-639-3 (ISBN)
Public defence
2010-06-11, E1, Lindstedtsvägen 3, entréplan, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100705Available from: 2010-06-01 Created: 2010-06-01 Last updated: 2010-07-05Bibliographically approved
2. Lubrication and Surface Properties of Adsorbed Layers of Polyelectrolytes and Proteins
Open this publication in new window or tab >>Lubrication and Surface Properties of Adsorbed Layers of Polyelectrolytes and Proteins
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Friction forces between protein / polyelectrolyte layers, adsorption properties of proteins, and conformational changes due to variation in electrolyte concentration have been investigated. The aim was to obtain better understanding of adsorbed layer properties, with focus on the relation between layer structure and lubrication capabilities. The major techniques used were AFM (atomic force microscope) with colloidal probe for normal force and friction measurements together with QCM-D (quartz crystal microbalance with dissipation) for measurement of adsorption and conformational changes of adsorbed layers.

A comparison between some techniques for calibration of the AFM instrument for friction measurements was made to find the most suitably one for colloidal probe friction measurements in aqueous solutions. It is suggested that the normal and torsional Sader methods are preferred in combination with torsional detector sensitivity measurement, for which one new methodology has been proposed.

Adsorption was studied for bovine serum albumin, cytochrome c, myoglobin and mucin, whereas conformational changes of the adsorbed layer were monitored only for mucin. It was found that it was essential to take into account bulk density and viscosity changes for correct interpretations of QCM data when studying the effect of changes in electrolyte type and concentration on preadsorbed layers of mucin, and also when having different (high) concentrations of proteins in the measuring solution. The adsorbed amount of proteins appears to depend on the strength of the surface attachment, in such a manner that a too high affinity reduces the adsorbed amount.

Friction properties in aqueous solution have been studied for adsorbed layers of PEO45MEMA:METAC co-polyelectrolytes, with varying density of grafted PEO45 side chains and varying charge density, as well as for a naturally occurring polyelectrolyte (chitosan) and the glycoprotein mucin. These polymers were used to cover a wide range of different types of adsorbed layers and interactions to gain a better understanding of friction mechanisms and demands on layer properties for achieving favourable lubrication. It was found that the common features of low friction layers are that no attractive forces are present, and that excluded volume and / or electrostatic forces counteract chain interpenetration under load.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. vii, 59 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:16
Keyword
biochemistry, biomedical engineering
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-4663 (URN)978-91-7178-891-7 (ISBN)
Public defence
2008-03-27, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100903Available from: 2008-03-07 Created: 2008-03-07 Last updated: 2010-09-03Bibliographically approved

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Pettersson, TorbjörnDėdinaitė, Andra

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