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  • 1.
    Feldötö, Zsombor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Structures of Polyelectrolyte Multilayers and Preasorbed Mucin: The Influence of Counterions2010Doctoral 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.

     

  • 2.
    Feldötö, Zsombor
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Braesch-Andersen, Sten
    Mabtech AB, Sweden.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Institute for Surface Chemistry, Sweden.
    Adsorption of IgG on/in a PAH/PSS Multilayer Film: Layer Structure and Cell Response2011In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 354, no 1, p. 31-37Article in journal (Refereed)
    Abstract [en]

    The binding of immunogloblulins (IgG) (mouse monoclonal recognizing IFN gamma) on precoated polystyrene or silica surfaces by the layer-by-layer technique has been investigated with QCM-D and DPI. The aim of the work was to increase the sensitivity of the conventional enzyme-linked immunosorbent spot (ELISpot) assay. The polyelectrolytes used to build the multilayers were poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) alternately adsorbed from 150 mM NaCl. The multilayer build up is linear and the internal structure of the PAH/PSS multilayer is compact and rigid as observed by low relative water content (20-25%) and high layer refractive index (n similar to 1.5) after the formation of five bilayers. Incorporation of IgG within the PAH/PSS multilayer did not give rise to overcharging and did not affect the linear build up. ELISpot test on PAH/PSS multilayer modified polystyrene wells showed that the cytokine response was significantly smaller than on the regular PVDF backed polystyrene wells. This may be due to the compact and rigid nature of the PAH/PSS multilayer, which does not allow formation of the kind of three dimensional support needed to achieve bioactive IgG binding to the surface. Immunological tests of the polyelectrolyte multilayers in the absence of IgG showed that 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.

  • 3.
    Feldötö, Zsombor
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Mucin-electrolyte interactions at the solid-liquid interface probed by QCM-D2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 7, p. 3348-3357Article in journal (Refereed)
    Abstract [en]

    The interaction between mucin and ions has been investigated by employing the quartz crystal microbalance technique with measurement of energy dissipation. The study was partially aimed at understanding the adsorption of mucin on surfaces with different chemistry, and for this purpose, surfaces exposing COOH, OH, and CH3 groups were prepared. Mucin adsorbed to all three types of functionalized gold surfaces. Adsorption to the hydrophobic surface and to the charged hydrophilic surface (COOH) occured with high affinity despite the fact that in the latter case both mucin and the surface were negatively charged. On the uncharged hydrophilic surface exposing OH groups, the adsorption of mucin was very low. Another aim was to elucidate conformational changes induced by electrolytes on mucin layers adsorbed on hydrophobic surfaces from 30 mM NaNO3. To this end, we investigated the effect of three electrolytes with increasing cation valance: NaCl, CaCl2, and LaCl3. At low NaCl concentrations, the preadsorbed layer expands, whereas at higher concentrations of NaCl the layer becomes more compact. This swelling/compacting of the mucin layer is fully reversible for NaCl. When the mucin layer instead is exposed to CaCl2 or LaCl3, compaction is observed at I mM. For CaCl2, this process is only partially reversible, and for LaCl3, the changes are irreversible within the time frame of the experiment. Finally, mucin interaction with the DTAB cationic surfactant in an aqueous solution of different electrolytes was evaluated with turbidimetry measurements. It is concluded that the electrolytes used in this work screen the association between mucin and DTAB and that the effect increases with increasing cation valency.

  • 4.
    Feldötö, Zsombor
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Varga, Imre
    Eotvos Lorand University, Institute of Chemistry, Budapest, Hungary.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Influence of Salt and Rinsing Protocol on the Structure of PAH/PSS Polyelectrolyte Multilayers2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 22, p. 17048-17057Article in journal (Refereed)
    Abstract [en]

    A quartz crystal microbalance (QCM) and dual polarization interferometry (DPI) have been utilized to study how the structure of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) multilayers is affected by the rinsing method (i.e., the termination of polyelectrolyte adsorption). The effect of the type of counterions used in the deposition solution was also investigated, and the polyelectrolyte multilayers were formed in a 0.5 M electrolyte solution (NaCl and KBr). From the measurements, it was observed that thicker layers were obtained when using KBr in the deposition solution than when using NaCl. There different rinsing protocols have been studied: (i) the same electrolyte solution as used during multilayer formation. (ii) pure water, and (iii) first a salt solution (0.5 M) and then pure water. When the multilayer with PAH as the outermost layer was exposed to pure water, an interesting phenomenon was discovered: a large change in the energy dissipation was measured with the QCM. This could be attributed to the swelling of the layer, and from both QCM and DPI it is obvious that only the outermost PAH layer swells (to a thickness of 25-30 nm) because of a decrease in ionic strength and hence an increase in intra- and interchain repulsion. whereas the underlying layers retain a very rigid and compact structure with a low water content. Interestingly, the outermost PAH layer seems to obtain very similar thicknesses in water independent of the electrolyte used for the multilayer buildup. Another interesting aspect was that the measured thickness with the DPI evaluated by a single-layer model did not correlate with the estimated thickness from the model calculations performed on the QCM-D data. Thus, we applied a two-layer model to evaluate the DPI data and the results were in excellent agreement with the QCM-D results. To our knowledge. this evaluation of DPI data has not been done previously.

  • 5.
    Kaufman, E. D.
    et al.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Belyea, J.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Johnson, M. C.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Nicholson, Z. M.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Ricks, J. L.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Shah, P. K.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Bayless, M.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Feldötö, Zsombor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Franzen, S.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Probing Protein Adsorption onto Mercaptoundecanoic Acid Stabilized Gold Nanoparticles and Surfaces by Quartz Crystal Microbalance and ζ-Potential Measurements2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 11, p. 6053-6062Article in journal (Refereed)
    Abstract [en]

    The adsorption characteristics of three proteins [bovine serum albumin (BSA), myoglobin (Mb), and cytochrome c (CytC)] onto self-assembled monolayers of mercaptoundecanoic acid (MUA) on both gold nanoparticles (AuNP) and gold surfaces (Au) are described. The combination of quartz crystal microbalance measurements with dissipation (QCM-D) and pH titrations of the zeta-potential provide information on layer structure, surface coverage, and potential. All three proteins formed adsorption layers consisting of an irreversibly adsorbed fraction and a reversibly adsorbed fraction. BSA showed the highest affinity for the MUA/Au, forming an irreversibly adsorbed rigid monolayer with a side-down orientation and packing close to that expected in the jamming limit. In addition, BSA showed a large change in the adsorbed mass due to reversibly bound protein. The data indicate that the irreversibly adsorbed fraction of CytC is a monolayer structure, whereas the irreversibly adsorbed Mb is present in form of a bilayer. The observation of stable BSA complexes on MUA/AuNPs at the isoelectric point by zeta-potential measurements demonstrates that BSA can sterically stabilize MUA/AuNP. On the other hand, MUA/AuNP coated with either Mb or CytC formed a reversible flocculated state at the isoelectric point. The colloidal stability differences may be correlated with weaker binding in the reversibly bound overlayer in the case of Mb and CytC as compared to BSA.

  • 6.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Feldötö, Zsombor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dėdinaitė, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    The Effect of Salt Concentration and Cation Valency on Interactions Between Mucin-Coated Hydrophobic Surfaces2008In: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 134, p. 1-10Article in journal (Refereed)
    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.

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