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  • 101.
    Kronberg, B
    et al.
    YKI – Ytkemiska institutet.
    Stenius, P
    YKI – Ytkemiska institutet.
    The effect of surface polarity on the adsorption of nonionic surfactants. IThermodynamic considerations1984Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 102, s. 410-417Artikel i tidskrift (Refereegranskat)
  • 102.
    Kronberg, B
    et al.
    YKI – Ytkemiska institutet.
    Stenius, P
    YKI – Ytkemiska institutet.
    Igeborn, G
    The effect of surface polarity on the adsorption of nonionic surfactants. II Adsorption on poly(methyl methacrylate) latex1984Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. A-405, s. 418-423Artikel i tidskrift (Refereegranskat)
  • 103.
    Kugge, C
    et al.
    YKI – Ytkemiska institutet.
    Daicic, J
    YKI – Ytkemiska institutet.
    Shear response of concentrated calcium carbonate suspensions2004Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 271, s. 241-248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rheology of concentrated calcium carbonate suspensions is investigated with respect to addition of solution and dispersion polymers. System materials and composition are chosen to be similar, generically, to those in use in the coating of paper. Specifically, we investigate the particle volume fraction dependence of the relative viscosity, using both capillary and steady-shear concentric cylinder measurement methods to cover a broad range of concentrations. The results are interpreted in terms of semi-empirical models, such as the Krieger–Dougherty model. Oscillatory shear measurements are also employed to investigate the viscoelastic behavior of the concentrated suspensions. The measurements indicate that a common solution polymer thickener, carboxymethyl cellulose (CMC), causes depletion flocculation of calcium carbonate suspensions.

  • 104.
    La Force, G
    et al.
    YKI – Ytkemiska institutet.
    Sarthz, B
    YKI – Ytkemiska institutet.
    A study of the isotropic phase in the ternary system n-octylamine-p-xylene-water using NMR and light scattering1971Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 37, s. 254-263Artikel i tidskrift (Refereegranskat)
  • 105. Larson, I
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Coagulation of quartz particles in aqueous solutions of copper (II)1998Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 208, s. 399-404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The colloidal stability of quarts suspension was determined over a wide range of pH in aqueous copper nitrate where the state of Cu(II) is changed from mainly aqua-ions and monohydroxyl complexes and colloidal precipitated copper hydroxide at higher pH. Two regions of instability were observed and in both cases the particles were shown to have low electrophoretic mobility. In the neutral pH region, the uptake of Co(II) was sufficient to reduce the mobility of the particles to zero, while in the high pH region evidence suggested coagulation between precipitated Cu(OH)2 and the quarts particles. It was shown that in all cases the coagulation was reversible and that the uptake of Cu(II) was dependent on the uncharged surface hydroxyl density. Studies of the coagulation kinetics showed that extended time scale were involved ( several minutes in the neutral pH region to tens of minutes at high pH ).

  • 106.
    Larsson, N
    et al.
    YKI – Ytkemiska institutet.
    Siffert, B
    Formation of lysozyme-containing crystals of montmorrillonite1983Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 93, s. 424-431Artikel i tidskrift (Refereegranskat)
  • 107. Larsson, N
    et al.
    Stenius, P
    YKI – Ytkemiska institutet.
    Eriksson, JC
    Maripuu, R
    Lindberg, B
    ESCA studies of sulfated polyethylene surfaces modified by adsorption ofpolyethyleneimine and colloidal silica particles1982Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 90, s. 127-136Artikel i tidskrift (Refereegranskat)
  • 108. Lassen, B
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Competitive protein adsorption at plasma polymer surfaces1997Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 186, s. 9-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Competetive adsorption from a ternary mixture of human serum albumin (HSA), human IgG, and human fibrinogen (FGN) at concentrations corresponding to blood plasma diluted 1/100 was investigated with the combination of Total Internal Reflection Fluorescence spectroscopy (TIRF) and ellipsometry. As substrates, three different plasma polymer surfaces, representing different surface charge and surface energy, were prepared from hexamethyldisiloxane (PP-HMDSO), acrylic acid (PP-AA), and 1,2-diaminocyclohexane (PP-DACH). In addition, adsorption from single and binary protein systems was investigated with ellipsometry. At the hydrophobic PP-HMDSO little or no displacement of any of the proteins was observed. The adsorbed layer was dominated by HSA and IgG, although Fgn was also present to a smaller extent. On PP-DACH and PP-AA, representing positively and negatively charged hydrophilic surfaces, respectively, Fgn completely dominated the adsorbed layer while HSA was almost absent and IgG was present only at a very low level.

  • 109. Lassen, B
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Competitive protein adsorption studied with TIRF and ellipsometry1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 179, s. 470-477Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Total internal reflection fluorescence (TIRF) and ellipsometry have been used to study competitive protein adsorption to a hydrophobic model surface prepared by radio frequency plasma deposition of hexamethyl disiloxane on silicon. Single, binary, and ternary protein solutions of human serum albumin (HSA), IgG, and fibrogen (Fgn) at concentrations corresponding to 1/100 of those in blood plasma were investigated. It is shown that by employing the combination of ellipsometry and TIRF, information on both the total adsorbed amount and the composition of the adsorbed protein layer can be obtained. It was found that adsorbed HSA is not displaced by IgG and/or Fgn to any large extent. IgG and HSA dominate the adsorption from the ternary protein mixture, although fibrinogen is also present in the adsorbed layer to a smaller extent.

  • 110. Lassen, B
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Structure of protein layers during competitive adsorption1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 180, s. 339-349Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of protein layers during competitive adsorption was studied with ellipsometry. Single, binary, and ternary protein solutions of human serum albumin (HSA), IgG, and fibrinogen (Fgn) were investigated at concerntrations corresponding to blood plasma diluted 1/100. As a model surface, hydrophobic hexamethyldisiloxane (HMDSO) plasma polymer modified silica was used. By using multiambient media measurements of the bare substrate prior to protein adsorption the adsorbed amount as well as the thickness and refractive index of the adsorbed protein layer could be followed in situ and in real time. Under conditions used in these experiments neither IgG nor fibrinogen could fullydisplace serum albumin from the interface. The buildup of the protein layer occured via different mechanisms for the different protein systems. Fgn adsorbed in a rather flat orientation at low adsorbed amounts, while at higher surface coverage the protein reoriented to a more upright orientation in order to accommodate more molecules in the adsorbed layer. IgG adsorption proceeded mainly end on with little reorientation or conformational change on adsorption. Finally, for HSA an adsorbed layer thickness greater than the molecular dimensions was observed at high concentrations ( although not at low ), indicating that aggregates or multilayers formed on HMDSO plasma polymer surfaces. For all protein mixtures the adsorbed layer structure and buildup indicated that Fgn was the protein dominating the adsorbed layer, although HSA partially blocked the adsorption of this protein. At high surface concentration, HSA/Fgn mixtures show an abrupt change in both adsorbed layer thickness and refractive index suggesting, e.g., an interfacial phase transition of the mixed protein layer. A similar but less pronounced behavior was observed for HSA/IgG. For IgG/Fgn and HSA/Fgn a buildup of the adsorbed layer similar to that displayed by Fgn alone was observed.

  • 111.
    Li, H.
    et al.
    University of Western Australia, Australia.
    Choi, Y. S.
    University of Western Australia, Australia.
    Rutland, Mark W.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. KTH Royal Institute of Technology, Sweden.
    Atkin, R.
    University of Western Australia, Australia.
    Nanotribology of hydrogels with similar stiffness but different polymer and crosslinker concentrations2020Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 563, s. 347-353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hypothesis: The stiffness has been found to regulate hydrogel performances and applications. However, the key interfacial properties of hydrogels, like friction and adhesion are not controlled by the stiffness, but are altered by the structure and composition of hydrogels, like polymer volume fraction and crosslinking degree. Experiments: Colloidal probe atomic force microscopy has been use to investigate the relationship between tribological properties (friction and adhesion) and composition of hydrogels with similar stiffness, but different polymer volume fractions and crosslinking degrees. Findings: The interfacial normal and lateral (friction) forces of hydrogels are not directly correlated to the stiffness, but altered by the hydrogel structure and composition. For normal force measurements, the adhesion increases with polymer volume fraction but decreases with crosslinking degree. For lateral force measurements, friction increases with polymer volume fraction, but decreases with crosslinking degree. In the low normal force regime, friction is mainly adhesion-controlled and increases significantly with the adhesion and polymer volume fraction. In the high normal force regime, friction is predominantly load-controlled and shows slow increase with normal force. 

  • 112.
    Li, P
    et al.
    KTH Royal Institute of Technology, Sweden.
    Jansson, M
    YKI – Ytkemiska institutet. KTH Royal Institute of Technology, Sweden.
    Stilbs, P
    Kungliga Tekniska Högskolan.
    An investigation on the influence of intermolecular interactions on the dynamics and molecular order of micellized zwitterionic surfactants1991Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 142, s. 593-595Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of intramolecular as well as intermolecular interactions on the dynamics of micellized mixtures of decyldimethylammoniopropanesulfonate, a zwitterionic surfactant with an anionic surfactant (lithium decyl sulfate) and a cationic surfactnat (decylammonium acetate), have been studied by 13C multifield NMR relaxation. The experimental results, as analyzed by a two-step spin relaxation model, suggest that, in contrast to liquid crystalline systems, intramolecular interactions alone determine the order parameter profile and the local chain dynamics.

  • 113. Liljekvist, P
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Comparing decyl-β-maltoside and octaethyleneglycol mono n-decyl ether in mixed micelles with dodecyl benzenesulfonate. 1. Formation of mixed micelles2000Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 222, s. 159-164Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study the mixed micelle behaviour of an alkyl polyglycoside is compared to a surfactant of polyoxyethylene type, by means of surface tension measurements. The two nonionic surfactants are compared in mixed micelle systems together with an anionic surfactant. The surfactant mixtures are: decyl-b-maltoside (C10M) together with dodecyl benzenesulfonate (C12BS) and octaethyleneglycol mono n- decyl ether (C10EO8) together with C12BS. The mixture of C10M and C10EO8 is also studied. Critical micelle concentration (CMC) and the concentration at which the surface tension reduction is 20 mNm-1 (C20) are determined at different mixing ratios of the surfactant mixtures. By applying the non-ideal mixed micelle theory, interaction parameters at CMC (bCMC) and C20 (bC20) are calculated for the surfactant mixtures. The results show that the C10M - C12BS mixture has a bCMC parameter of -2.1, whereas the bCMC parameter for the C10EO8-C12BS mixture is -3.3, indicating a weaker net attractive interaction between C10M and C12BS than between C10EO8 and C12BS. This is attributed to a small negative and positive charge of the respective nonionic surfactants. This is supported by a slightly negative bCMC parameter obtained for the surfactant mixture C10M - C10EO8, indicating a small net attractive interaction between the two nonionic surfactants.

  • 114. Liljekvist, P
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Comparing decyl-β-maltoside and octaethyleneglycol mono n-decyl ether in mixed micelles with dodecyl benzenesulfonate. 2. Interaction of mixed micelles with polyvinylpyrrolidone2000Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 222, s. 165-169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interaction between polyvinylpyrrolidone (PVP) and a mixture of anionic and nonionic surfactants have been investigated by surface tension measurements. The surfactant mixtures are decyl-b-maltoside (C10M) together with dodecyl benzenesulfonate (C12BS) and octaethyleneglycol mono n-decyl ether (C10EO8) together with C12BS. Surface tension measurements of the surfactant mixtures in presence of PVP show that C10EO8 competes more effectively than C10M with PVP in the interaction with C12BS.

  • 115. Lindblom, G
    et al.
    Lindman, B
    YKI – Ytkemiska institutet.
    Mandell, L
    YKI – Ytkemiska institutet.
    A study of counter-ion binding to reversed micelles by nuclear magnetic quadrupole relaxation of 81Br1970Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 34, s. 262-271Artikel i tidskrift (Refereegranskat)
  • 116.
    Liu, Chao
    et al.
    KTH Royal Institute of Technology, Sweden.
    Thormann, Esben
    DTU Technical University of Denmark, Denmark.
    Tyrode, Eric
    KTH Royal Institute of Technology, Sweden.
    Claesson, Per M.
    RISE., SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Charge regulation and energy dissipation while compressing and sliding a cross-linked chitosan hydrogel layer2015Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 443, s. 162-169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interactions between a silica surface and a surface coated with a grafted cross-linked hydrogel made from chitosan/PAA multilayers are investigated, utilizing colloidal probe atomic force microscopy. Attractive double-layer forces are found to dominate the long-range interaction over a broad range of pH and ionic strength conditions. The deduced potential at the hydrogel/aqueous interface is found to be very low. This situation is maintained in the whole pH-range investigated, even though the degree of protonation of chitosan changes significantly. This demonstrates that pH-variations change the concentration of counterions within the hydrogel to keep the interior close to uncharged, which is similar to what has been observed for polyelectrolyte brushes. Changes in pH and ionic strength affect the adhesion force and the friction force between the silica surface and the hydrogel layer, but not the friction coefficient. This suggests that the main energy dissipation mechanism arises from processes occurring within the hydrogel layer, rather than at the silica/hydrogel interface, and we suggest that it is related to stretching of polymer chains between the cross-linking points. We also find that an increased cross-linking density, from 40% to 100%, in the hydrogel reduces the friction coefficient.

  • 117.
    Liu, Xiaoyan
    et al.
    KTH Royal Institute of Technology, Sweden.
    Dedinaite, Andra
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Polymer och fiber. KTH Royal Institute of Technology, Sweden.
    Nylander, Tommy
    Lund University, Sweden.
    Dabkowska, Aleksandra P.
    Lund University, Sweden.
    Skoda, Maximilian
    Rutherford-Appleton Lab, UK.
    Makuska, Ricardas
    Vilnius University, Lithuania.
    Claesson, Per M.
    RISE., SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Association of anionic surfactant and physisorbed branched brush layers probed by neutron and optical reflectometry2015Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 440, s. 245-252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pre-adsorbed branched brush layers were formed on silica surfaces by adsorption of a diblock copolymer consisting of a linear cationic block and an uncharged bottle-brush block. The charge of the silica surface was found to affect the adsorption, with lower amounts of the cationic polyelectrolytedepositing on less charged silica. Cleaning under basic conditions rendered surfaces more negatively charged (more negative zeta-potential) than acid cleaning and was therefore used to increase polyelectrolyte adsorption. The structure of adsorbed layers of the diblock copolymer was as determined by neutron reflectometry found to be about 70 nm thick and very water rich (97%). Interactions between the anionic surfactant sodium dodecylsulfate (SDS) and such pre-adsorbed diblock polymer layers were studied by neutron reflectometry and by optical reflectometry. Optical reflectometry was also used for deducing interactions between the individual blocks of the diblock copolymer and SDS at the silica/aqueous interface. We find that SDS is readily incorporated in the diblock copolymer layer at low SDS concentrations, and preferentially co-localized with the cationic block of the polymer next to the silica surface. At higher SDS concentrations some desorption of polyelectrolyte/surfactant complexes takes place.

  • 118.
    Liu, Xiaoyan
    et al.
    KTH Royal Institute of Technology, Sweden.
    Yun, Sang Ho
    Sungkyunkwan University, South Korea.
    Claesson, Per M.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. KTH Royal Institute of Technology, Sweden.
    Frictional behavior of micro-patterned silicon surface2015Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 456, s. 76-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A micro-patterned silicon surface, consisting of depressions with walls having a tilt angle of 30°, was created by photolithography followed by etching. The friction forces in single asperity contact acting between such a surface and an AFM tip was measured in air. This allowed elucidation of the validity of some common friction rules for this particular situation where a small tip traces a surface having roughness features that are significantly larger than the tip itself. The rules that was compared with our data were Amontons' first rule of friction stating that the friction force should be proportional to the load; Amontons' third rule stating that the friction force should be independent of sliding speed, and Euler's rule providing a relation between slope angle and friction coefficient. We found that both nanoscale surface heterogeneities and the μm-sized depressions affect friction forces, and considerable reproducible variations were found along a particular scan line. Nevertheless Amontons' first rule described average friction forces well. Amontons' third rule and Euler's rule were found to be less applicable to our system.

  • 119. Lundell, C.
    et al.
    De Hoog, E.H.A.
    Tromp, R.H.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Effects of confined geometry on phase-separated dextran/gelatine mixtures exposed to shear2005Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 288, nr 1, s. 222-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of shear on aqueous phase-separated dextran/fish gelatine mixtures with a total concentration of 5 and 10% was studied in a confined geometry. It was measured as a function of composition, strain rate and gap size. This was done by using both small-angle light scattering and a shear cell combined with a confocal laser scanning microscope. At a total polymer concentration of 5%, small-angle light scattering results showed that up to 100 s-1 the deformation of the domains increases with the strain rate. At strain rates less than 100 s-1, the response of the system to strain is dominated by strain rate-dependent deformation. At a higher strain rate there might be balance between break-up and re-coalescence. At a total concentration of 10%, small effects of the gap size were found. In confined geometry, the coalescence rate was faster than expected from viscous hydrodynamic growth. The microscope images showed that the gelatine-enriched phase forms a wetting layer on the surface of the glass wall. The degree of wetting appears to increase with increasing the strain rate up to 60 s -1 and decreases again at higher strain rates. © 2005 Elsevier Inc. All rights reserved.

  • 120.
    Lundgren, SM
    et al.
    YKI – Ytkemiska institutet.
    Ruths, M
    Danerlöv, K
    YKI – Ytkemiska institutet.
    Persson, K
    YKI – Ytkemiska institutet.
    Effects of unsaturation on film structure and friction of fatty acids in a model base oil2008Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 326, nr 2, s. 530-536Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The normal and friction forces between layers of three fatty acids (stearic, oleic, and linoleic acid) and a rosin acid (dehydroabietic acid) have been measured in n-hexadecane with a surface forces apparatus. Stearic, oleic, and dehydroabietic acid form loose-packed monolayers on mica surfaces when adsorbed from dry n-hexadecane. Linoleic acid forms an additional dimer layer between monolayercovered surfaces, where it is stabilized by interactions between the double-bond-rich regions of the molecules. The monolayers formed by linoleic and dehydroabietic acid are thinner than the ones formed by stearic and oleic acid, but are not as easily removed from between the mica surfaces when the load or pressure is increased. The friction force increased linearly with load in all systems, and the friction coefficient increased with increasing unsaturation. Linoleic acid showed two regimes of linear friction with increasing load, corresponding to two different film thicknesses. Its friction was sensitive to sliding speed and adsorption time, and the thinner film observed at higher load had a lower friction coefficient. Such features were not observed for stearic and oleic acid, where the monolayers were removed and the friction coefficient changed to that of pure n-hexadecane at a pressure of 3.5 MPa.

  • 121. Lundin, M
    et al.
    Sandberg, T
    Caldwell, KD
    Blomberg, E
    YKI – Ytkemiska institutet.
    Comparison of the adsorption kinetics and surface arrangement of "as received" and purified bovine submaxillary gland mucin (BSM) on hydrophilic surfaces2009Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 336, nr 1, s. 30-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of bovine serum albumin (BSA) as impurity in a commercial bovine submaxillary gland mucin preparation (BSM; Sigma M3895) on the adsorption of BSM to hydrophilic surfaces (mica and silica) has been studied in terms of adsorption kinetics, amount and structure of the formed adlayer. The Surface Force Apparatus (SFA) was used to gain information about the extended and compressed structure of adsorbed "as received" BSM, purified BSM, BSA extracted from the "as received" BSM and mixtures of the latter purified proteins. The adsorbed amount was estimated using a combination of X-ray Photoelectron Spectroscopy (XPS), Enzyme-Linked Immuno Sorbent Assay (ELISA), Enzyme-Linked Lectin Assay (ELLA), Dual Polarization Interferometry (DPI) and Quartz Crystal Microbalance (QCM-D) measurements. Under the used conditions, purified BSM showed very low affinity for silica and only small amounts were found to adsorb on mica. Initially, the BSM molecules adopted an extended conformation on the mica surface with tails extending into the bulk phase. These tails were irreversibly compressed into a very thin (10 Å) layer upon applying a high load. "As received" BSM formed considerably thicker compressed layers (35 Å); however, the extended layer structure was qualitatively the same. When mixtures of purified BSM and BSA were coadsorbed on mica, a 9 wt-% albumin content gave a comparable layer thickness as the "as received" BSM and from XPS data we draw the conclusion that the albumin content in the layer adsorbed from "as received" BSM was approximately 5 wt-%. Adsorption from an equal amount of BSM and BSA revealed that even though the amount of BSM is scarce in the mixed layer, the few BSM molecules have a drastic effect on the adsorbed thickness and structure. Clearly, this study shows the importance of characterizing the mucin used since differences in purity give rise to different adsorption behaviours in terms of both adsorbed amount and layer structure.

  • 122.
    Maijgren, B
    et al.
    YKI – Ytkemiska institutet.
    Ödberg, L
    YKI – Ytkemiska institutet.
    Surface tension data from slight deformations of the surface : the ringmethod1982Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 88, s. 197-203Artikel i tidskrift (Refereegranskat)
  • 123.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Ellipsometry studies of protein adsorption at lipid surfaces1994Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 168, s. 247-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of human serum albumin (HSA), IgG and fibrinogen at lipid surfaces was investigated with in situ ellipsometry. It was found that the adsorbed amount of these proteins at phosphatidylcholine (PC) and phosphatidylinositol (PI) surfaces was smaller than that at (hydrophilic) silica and (hydrophobic) methylated silica surfaces. PC and PI surfaces were quite similar with respect to the adsorption of these proteins. More precisely, the adsorption of HSA, IgG and fibrinogen at PC is lower than that at methylated silica roughly by a factor of 3, 15 and 100, respectively, corresponding to an adsorbed amount of 0.30 mg/m2, 0.20 mg/m2 and 0.05 mg/m2, respectively. The adsorption of lysozyme at PI was significantly larger than that of HSA, IgG and fibrinogen, but still smaller than that of lysozyme at silica and methylated silica. At phosphatidic acid (PA), the adsorption of all the proteins investigated was significantly larger than that at PC and PI. In fact, the adsorption at PA resembles that at silica and methylated silica more than that at PC and PI. These findings are correlated to previous results on the influence of the surface composition of colloidal drug carriers on their endocytosis.

  • 124.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Ellipsometry studies of protein layers adsorbed at hydrophobic surfaces1994Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 166, s. 333-342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of some model proteins, human serum albumin (HSA), IgG, fibrinogen and lysozyme, at methylated silica surfaces was investigated with in situ ellipsometry. By performing studies with the bare substrate at two different ambient refractive indices, and by performing 4-zone averaging, the adsorbed amount, the adsorbed layer thickness and the mean adsorbed layer refractive index are obtained. The adsorbed amounts obtained for the proteins agree well with previous results. The adsorbed layer thicknesses vary strongly between the proteins. Thus, at adsorption plateau, the adsorbed layer thicknesses (del) obtained for HSA, lysozyme, IgG and fibrinogen are 4±2 nm, 11±2 nm, 18±2 nm and 28±2 nm, respectively. The build-up of the adsorbed layers proceeds differently for different proteins. Thus, for fibrinogen, both del and the adsorbed layer mean refractive index (nf) increase monotonically up to about 4 mg/m2. For IgG, on the other hand, del is essentially independent of the adsorbed amount, whereas nf increases linearly. Finally, the adsorbed layer formed by lysozyme is more compact than those formed by fibrinogen, IgG and HSA. These findings are discussed in terms of adsorbed layer structure.

  • 125.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Formation of adsorbed protein layers1998Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 207, s. 186-199Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Not available

  • 126.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Protein adsorption at phospholipid surfaces1995Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 172, s. 106-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of human serum albumin (HSA), IgG, fibronectin and fibrinogen at phospholipid surfaces was studied with in situ ellipsometry. For comparison, a model hydrophobic surface (methylated silica) and a model hydrophilic surface (silica) were also included in the study, as was a surface coated with an ethylene oxide/propylene oxide (EO/PO) block copolymer. The phospholipid head group composition was found to have a major effect on the serum protein adsorption. Surfaces with either no net charge or shielded charges, e. g. phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM) and phosphatidylinositol (PI) or ganglioside GM1, generally give a low adsorption of serum proteins of importance for opsonization, in analogy to the performance of adsorbed water-soluble polymers (e. g. EO/PO block copolymers), while those containing either unprotected charges, e. g. phosphatidic acid (PA), diphosphatidylglycerol (DPG), phosphatidylserine (PS) and silica, or hydrophobic domains (methylated silica), result in a high opsonin protein adsorption. However, the effects studied are complex, and different serum proteins generally behave quite differently at a given surface.

  • 127.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Masquelier, M
    Pålsson, M
    Peterson, C
    Adsorption of apolipoprotein B at phospholipid model surfaces1995Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 172, s. 485-493Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of apolipoprotein B (Apo B) at a series of surfaces was investigated with in situ ellipsometry. For silica and methylated silica, the adsorbed amount (G), the adsorbed layer thickness (del) and the mean adsorbed layer refractive index (nf) were obtained by a procedure involving studies of the bare substrate at two different ambient refractive indices, as well as four-zone averaging. The adsorbed amount of Apo B is much higher at silica than at methylated silica. Despite this, the adsorbed layer thickness is the same at the two surfaces, and the adsorbed layer formation proceeds similarly. In both cases, the adsorbed layer formation occurs through the adsorption of Apo B molecules in an essentially random orientation, the difference between silica and methylated silica being the number of molecules adsorbed per unit area. Furthermore, the adsorption of Apo B at phospholipid surfaces was investigated. It was found that the adsorption at phosphatidylcholine (PC) was quite limited, whereas that at phosphatidic acid (PA) was substantial. Studies with mixed PA/PC layers showed that the Apo B adsorption depends on the mixed phospholipid layer composition in an essentially linear fashion. Finally, mixed phospholipid layers of PC and ganglioside GM1, as well as phosphatidylinositol (PI) layers, showed a dramatic preferential adsorption of Apo B over, e. g. human serum albumin (HSA), IgG, fibronectin and fibrinogen.

  • 128.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Blomberg, E
    YKI – Ytkemiska institutet.
    Claesson, P
    YKI – Ytkemiska institutet.
    Carlstedt, I
    Ljusegren, I
    Mucin layers on hydrophobic surfaces studied with ellipsometry and surface force measurements1992Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 151, s. 579-590Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The forces acting between layers of gastric mucins from rat (RGM) and pig (PGM) adsorbed on to hydrophobized mica surfaces were investigated by using the surface force technique, whereas information on the kinetics and the reversibility of the adsorption process was obtained with ellipsometry. From the surface force measurements, we found that the amount adsorbed from a 0.1 mg/ml RGM solution was 3.5±1.5 mg/m2 at adsorption equilibrium, within experimental error equal to that (about 3 mg/m2) found with ellipsometry. The forces obtained with RGM were purely repulsive, whereas those displayed by PGM were partially attractive. Dilution of the bulk solution caused only minor desorption and the interaction force between the RGM layers was only weakly dependent on the excess electrolyte concentration. Hence, steric forces predominate the interaction in the RGM system. Both RGM and PGM adsorb in a flat conformation, with compressed adsorbed layer thicknesses of 10-20 nm and 3-4 nm, respectively. The interaction force was essentially reversible on approach and separation for RGM, whereas 'relaxation effects' were prominent for PGM layers.

  • 129.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Burns, N
    Veide, A
    Electrostatic and hydrophobic effects of oligopeptide insertions on protein adsorption1998Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 204, s. 104-111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of oligopeptide insertions on the adsorption of the protein ZZ, where Z is the IgG binding domain of staphylococcal Protein A, was investigated by in situ ellipsometry. In particular, the interplay between hydrophobic and electrostatic interactions as driving force for adsorption was investigated by studying the effects of oligopeptide insertions of the type Tn(AlaTrpTrpPro), Na ((AlaTrpTrpLysPro)n), and Pn((AlaTrpTrpLysPro)n) on the adsorption at silica, methylated silica , and diaminocyclohexane (DACH) plasma polymer surfaces. For comparison, the adsorption of the inserted peptide stretches was also investigated. It was found that the adsorption of all the peptides increases with the molecular weight at methylated silica. At silica, only the Pn peptides were found to adsorb. The net negatively charged proteins modified through peptide insertions did not adsorb at the hydrophilic and negatively charged silica, irrespective of the peptide insertion, whereas an extensive adsorption was found for the posetively charged DACH surface for all the proteins investigated. For hydrophobic and negatively charged methylated silica, on the other hand, the peptide insertions were found to have a major influence on the protein interfacial behavior, and the adsorption followed the peptide stretch charge, thus increasing in the order ZZNn< ZZTn < ZZPn. These effects are discussed in terms of the relative importance of hydrophobic and electrostatic interactions as driving force for the adsorption.

  • 130.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Emoto, K
    Van Alstine, JM
    Effect of chain density on inhibition of protein adsorption by poly(ethylene glycol) based coatings1998Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 202, s. 507-517Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of interfacial chain density of poly( ethylene glycol) (PEG) on the adsorption of serum proteins was investigated by in situ ellipsometry. For terminal covalently grafted PEG of molecular weight 5000 an increased grafting density results in serum protein adsorption. At high interfacial chain density ( É 0.1 chain/nm2) , efficient protein rejection was observed, irrespective of the coupling chemistry used. Strongly adsorbed PEG-containing polymers behaved similarly to covalently attached PEG regarding inhibition of protein adsorption, independent of the nature of the underlying surface. The results are discussed in relation to the importance of the protein size in protein rejection by PEG coatings.

  • 131.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Lassen, B
    Competitive adsorption at hydrophobic surfaces from binary protein systems1994Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 166, s. 490-498Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of some model proteins, human serum albumin (HSA), IgG and fibrinogen, at silica made hydrophobic by either methylation or plasma deposition of HMDSO (hexamethyldisiloxane) was investigated with in situ ellipsometry and TIRF. Ellipsometry experiments of the simultaneous adsorption of HSA and either IgG or fibrinogen revealed a preferential adsorption of the latter proteins. This is seen not only from the total adsorbed amount, but also from the adsorbed layer thickness, as well as from the build-up of the adsorbed layer. However, in sequential adsorption experiments, where HSA was first allowed to adsorb, followed by rinsing and addition of either IgG or fibrinogen, the additional adsorption is quite limited. Consequently, when HSA is allowed to adsorb on its own at hydrophobic surfaces, it is not removed by either IgG or fibrinogen to any larger extent. Furthermore, preadsorbed HSA was not exchanged by HSA added after adsorption and rinsing, implying that the mechanism behind this effect is an ”irreversible” adsorption of HSA at hydrophobic surfaces, possibly originating from a surface-induced conformational change of HSA at these surfaces. Analogous findings were obtained with both methylated and HMDSO-treated surfaces, using both ellipsometry and TIRF.

  • 132.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Lassen, B
    Holmberg, K
    YKI – Ytkemiska institutet.
    Thomas, V
    Quash, G
    Effects of hydrophilization and immobilization on the interfacial behaviour of immunoglobulins1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 177, s. 70-78Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption and immobilization of rabbit anti-human immunoglobulin (rabbit IgG), as well as the effects on the amount and reactivity of bound rabbit IgG of rinsing with buffer and addition of bovine serum albumin (BSA) or human IgG, were investigated with ellipsometry, TIRF and enzyme immuno assay (EIA). It was found that although rabbit IgG readily adsorbs at hydrophobic hexamethyldisiloxane (HMDSO) plasma polymer surfaces, a substantial fraction of the adsorbed protein molecules are desorbed on rinsing with buffer. BSA was found to adsorb readily at the surfaces obtained after rinsing, although also this protein desorbed to a large extent on further rinsing with buffer. The adsorption of BSA causes a further reduction in the amount of rabbit IgG adsorbed. Immobilization of rabbit IgG to acrylic acid (AA) plasma polymer surfaces, achieved by covalent coupling via a strongly adsorbed PEG-PEI copolymer, was found to overcome the problem of desorption of rabbit IgG on rinsing with buffer or addition of BSA. Furthermore, non-specific adsorption was virtually absent after immobilization. However, covalently bound rabbit IgG reacted strongly with human IgG, as observed by ellipsometry, TIRF and EIA. The immobilization of rabbit IgG to hydrophilized surfaces was found to facilitate the interpretation of EIA results.

  • 133.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Lassen, B
    Van Alstine, JM
    Nilsson, U
    Adsorption of complement proteins C3 and C1q1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 178, s. 123-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface localization plays a key but ill defined role in activation of the Serum Complement System with or without related "opsonic" proteins. The adsorption of key complement components C3 and C1q and various opsonins, e. g., IgG, were therefore studied on different surfaces using in situ ellipsometry. The affinities of C3 and C1q for silica, methylated silica, and various phospholipid surfaces were shown to be largely reciprocal. While C3 adsorbed more extensively at (hydrophilic and negatively charged) silica than at (hydrophobic) methylated silica (3.1 versus 0.4 mg/m2, respectively) the opposite trend was observed for C1q (1.9 versus 2.6 mg/m2). C3 and C1q adsorbed in 10 to 15 nm thick layers on both silica and methylated silica. Each protein appeared to adsorb with consistent conformation and orientation on either surface. Adsorbed layer formation involves increased protein packing density, and molecular extension normal to the surface. Phospholipid head group properties strongly affect the adsorption of C3 and C1q at phospholipid coated surfaces. The saturation adsorption of C3 at phosphatidic acid was almost as significant as at silica, whereas the amount adsorbed at phosphatidylcholine was three times lower. C3 adsorption at phosphatidylinositol and various poly(ethylene glycol) modified surfaces was virtually absent, as was the adsorption of various opsonins. C1q adsorption was relatively low at all phospholipid and poly(ethylene glycol) coated surfaces investigated, more in the manner of IgG than C3. Preadsorption of IgG increased C1q deposition at phospholipid surfaces strongly. C3 and human serum albumin, but not C1q, showed appreciable hydrophobic affinity for a poly(ethylene glycol)-fatty acid ester of oleic acid. These results are discussed in relation to complement interaction with various surfaces and colloidal drug carriers.

  • 134.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Lassen, B
    Westin, J
    Gölander, C-G
    Larsson, R
    Nilsson, UR
    Adsorption of complement protein C3 at polymer surfaces1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 179, s. 163-172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of C3 at poly(methyl methacrylate) (PMMA) and poly(styrene) (PS) surfaces was investigated with in situ ellipsometry and compared to that at (hydrophilic and negatively charged) silica and (hydrophobic) methylated silica. The adsorption of C3 at PMMA was higher than that at PS, while the adsorbed layer thickness was the same for the two surfaces. For both PMMA and PS the adsorbed layer thickness (10±2 nm) corresponds rather closely to that of end-on oriented C3 molecules. The adsorption of C3 at PMMA and PS was found to be intermediate between that at silica and methylated silica, although the adsorbed layer thickness was similar for all surfaces. The competitive adsorption between C3, human serum albumin (HSA), and factor B was investigated with ellipsometry and total internal reflection fluorescence spectroscopy (TIRF). Addition of HSA after C3 preadsorption resulted in fractional C3 desorption for both PMMA and PS. Factor B deposition at PS after preadsorption of C3 and blocking with HSA was found to be largely due to specific binding to C3/C3b, while in the case of PMMA, factor B was largely accumulated through passive (displacement) adsorption.

  • 135.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Lindström, A-L
    Wärnheim, T
    Electrostatic effects on interfacial film formation in emulsion systems1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 179, s. 537-543Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption at silica from dilute emulsion systems was studied with in situ ellipsometry. In particular, the effects of electrostatic interactions on the adsorption rate and the adsorbed layer structure and formation was investigated by varying the emulsion droplet and surface charge, as well as the electrostatic screening, accomplished by varying pH and the excess electrolyte concentration. Electrostatic interactions were found to markedly affect the adsorption rate, but not the adsorbed layer structure or the mechanism for the adsorbed layer formation. For all cases investigated, the adsorbed layer thickness corresponds to emulsion droplets or multilamellar liposomes, and the adsorbed layer formation proceeds through attachment of emulsion droplets and/or multilamellar liposomes at the surface without extensive droplet spreading or liposome collapse. When the droplets and the surface are similarly charged, the adsorption is facilitated by increasing the electrostatic screening or by decreasing the emulsion droplet and surface charge, accomplished by increasing the excess electrolyte concentration and decreasing pH, respectively. When the droplets and the surface are oppositely charged, the adsorption rate is much higher than that observed when the droplets and the surface are similarly charged, although the adsorbed layer structure and the mechanism for the adsorbed layer formation are similar. Qualitatively, these effects may be understood by considering only electrostatic and van der Waals interactions.

  • 136.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Lindström, A-L
    Wärnheim, T
    Ellipsometry studies of interfacial film formation in emulsion systems1995Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 173, s. 297-303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility of using in situ ellipsometry for studies of the formation of interfacial films in emulsion systems was investigated. It was found that ellipsometry studies on dilute emulsion can provide information on both the adsorption kinetics, the adsorbed layer structure and the mechanisms for the adsorbed layer formation. At high electrolyte concentrations, the adsorption from a model o/w emulsion stabilized by egg lecithin was found to be more pronounced at hydrophilic and negatively charged silica than at hydrophobic methylated silica. Furthermore, the adsorbed layer thickness at both surfaces is smaller than the average droplet size, corresponding to either small or ”flattened” droplets or liposomes. The adsorbed layer thickness is smaller at methylated silica than at silica, presumably due to a larger degree of emulsion droplet or liposome spreading at this surface. In both cases, the adsorbed layer thickness is independent of the adsorbed amount, i. e. the adsorbed layer formation proceeds by attachment of droplets, which pack more densly with an increasing adsorbed amount.

  • 137.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Muller, D
    Lassen, B
    Sequential adsorption of human serum albumin (HSA), immunoglobulin G (IgG), and fibrinogen (Fgn) at HMDSO plasma polymer surfaces1997Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 193, s. 88-95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The sequential adsorption of human serum albumin (HSA), immunoglobulin G (IgG), and fibrinogen (Fgn) at hexamethyldisiloxane (HMDSO) plasma polymer surfaces was investigated with ellipsometry and total internal reflectance fluorescence spectroscopy (TIRF) as a function of adsorption time, pH, and excess electrolyte concentration. HSA was found to self-exchange very slowly (≈hours) at pH 7.2, irrespective of adsorption time in the range 90 seconds to 90 minutes. Preadsorbed HSA was exchanged by Fgn and IgG only to a limited extent irrespectively of pH (5≤pH≤8) and excess electrolyte concentration (5 mM≤Cs≤150 mM). At an excess electrolyte concentration of 150 mM, the sequential adsorption of Fgn and IgG was dramatically reduced by HSA preadsorption, irrespective of pH. At an excess electrolyte concentration of 5 mM, on the other hand, there were indications of second layer adsorption of Fgn and IgG.

  • 138.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Siegel, G
    Electrostatic and ion-binding effects on the adsorption of proteoglycans1995Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 170, s. 120-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of proteoheparan sulphate, a strongly negatively charged proteoglycan, at (hydrophobic) methylated silica surfaces was investigated with in situ ellipsometry. In particular, the effects of electrolytes in the physiological concentration ranges were studied. Both general electrostatic and cation-specific ion-binding effects were shown to be important for the interfacial behaviour of this macromolecule. While Ca2+ causes an increase in the adsorbed amount of proteoheparan sulphate at hydrophobic surfaces at physiological conditions, the effects of Mg2+ were the reverse, and of a much smaller magnitude. Similar finding were obtained for proteodermatan/-chondroitin sulphate, as well as for the heparan sulphate side-chains of proteoheparan sulphate. Furthermore, both Na+ and K+ cause an increase in the adsorption in certain concentration ranges, due to electrostatic reasons. However, Na+ and K+ were also found to oppose the effects of Ca2+. Moreover, the effects of K+ are of a smaller magnitude than those of Na+ and occur over a longer time-scale. Thus, general electrostatic effects, as well as cation-specific ion-binding effects are of importance for the biological performance of proteoglycans, e g, in the endothelial cell membrane.

  • 139.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Siegel, G
    Becker, A
    A model substrate for ellipsometry studies of lipoprotein deposition at the endothelium2001Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 240, s. 372-374Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Endothelial cell layers from umbilical cords were grown on methylated silica surfaces. Fluorescence microscopy showed this layer to be confluent and to consist of living cells. Initial ellipsometry measurements were performed to illustrate both the stability of the model surface in ellipsometry measurements and the Ca2+-dependent binding of lipoproteins at the cell-based substrate. The present substrate holds promise as a model substrate for in vitro investigations of lipoprotein deposition at the endothelium surface under close to in vivo conditions.

  • 140.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Siegel, G
    Wood, WG
    Ellipsometry studies of lipoprotein adsorption2000Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 224, s. 338-346Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of a number of lipoproteins, i.e., low-density lipoprotein (LDL), oxidized LDL (oxLDL), high-density lipoprotein (HDL), and lipoprotein (a), at silica and methylated silica as well as at the latter surface modified through adsorption of proteoheparan sulfate, was investigated with in situ ellipsometry at close to physiological conditions. It was found that LDL, oxLDL, HDL, and lipoprotein (a) all adsorbed more extensively at silica than at methylated silica. Upon exposure of the methylated silica surface to proteoheparan sulfate, this proteoglycan adsorbs through its hydrophobic moiety, thereby forming a layer similar to that in the biological system, with the polysaccharide chains forming brushes oriented toward the aqueous solution. Analogous to the biological system, both lipoprotein (a) and LDL were found to deposit at such surfaces, the latter particularly in the simultaneous presence of Ca2+. After HDL pre-exposure, however, no LDL deposition was observed, even at high LDL and Ca2+ concentrations. These findings correlate well with those obtained from clinical investigations on risk factors for atherosclerosis.

  • 141.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Van Alstine, JM
    Adsorption of poly(ethylene glycol) amphiphiles to form coatings which inhibit protein adsorption1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 177, s. 502-512Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of poly(ethylene glycol) (PEG)-esterified fatty acids at methylated silica, phosphatidic acid and phosphatidylcholine surfaces was investigated with in situ ellipsometry. For a series of PEG-fatty acid esters of ethoxy groups and acyl tails of the type Ci:j-EO151 (16≤i≤18, 0≤j≤2) adsorption at methylated silica was independent of bulk micellization, and plateau was reached below the critical micellization concentration (CMC). The plateau adsorbed amount for the investigated fatty acid esters was only weakly dependent on the nature of the hydrophobic moiety. Instead, saturation adsorption was largely determined by the interactions between PEG chains. Adsorption isotherms were therfore essentially identical on all three of the quite different surfaces. At saturation adsorption, the adsorbed layer thickness was 10-15 nm, while the average adsorbed layer concentration was 0.07 g/cm3. Formation of the PEG-surfactant coatings thus appeared to involve significant molecular alterations of PEG from a random coil. The ability of the PEG-ester coatings to inhibit protein adsorption was also investigated. At adsorption plateau, all coatings investigated displayed quite good ability to inhibit adsorption by a number of serum proteins. For all three surfaces studied this ability decreased below 0.2·CMC. These findings are discussed in relation to the ability of PEG-derivatized lipids to control the in vivo fate of colloidal drug carriers.

  • 142.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Veide, A
    Effects of amino acid composition on protein adsorption1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 178, s. 160-167Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption at silica and methylated silica of genetically engineered derivatives of Z and its dimer ZZ, where Z is a hydrophilic synthetic IgG binding domain derived from staphylococcal protein A, was studied with in situ ellipsometry. The protein modifications consisted of introducing short peptide stretches near the C-terminus of the protein. Using this approach, oligopeptide stretches containing hydrophobic tryptophan (Trp) or isoleucine (Ile) [(AlaTrpTrpPro)n or (AlaIleIlePro)n (0≤n≤2), denoted Tn and In, respectively] were introduced in the protein. For comparison, the adsorption of the inserted peptide stretches (Tn and In), as well as of Trp and Ile oligomers, was investigated as well. Increasing the number of Trp residues resulted in an increased adsorption for both ZZTn, ZTn, Tn, and Trpn. At a given number of Trp residues, the adsorbed amount of the ZZ derivatives is larger than that of the peptides, but about the same as that of the Z proteins. Analogous although somewhat smaller effects were obtained for the Ile-derivatized proteins. These results are discussed in terms of the "block copolymer" nature of the proteins. Theoretical calculations using a mean-field lattice model for block copolymer adsorption gave a qualitative agreement with the experimentally obtained results.

  • 143.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Xing, K
    Ljunglöf, A
    Confocal microscopy studies of trypsin immobilization on porous glycidyl methacrylate beads1999Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 220, s. 436-442Artikel i tidskrift (Refereegranskat)
  • 144. Manev, E
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    The influence of tetraalkylammonium counterions on the drainage and stability of thin films and foams stabilized by dilute aqueous solutions of sodium dodecyl sulphate1997Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 186, s. 493-497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It was demonstrated that the presence of tetraalkylammonium counterions in aqueous foams and thin film lamella stabilized by sodium dodecyl sulphate (at concentrations below the cmc) can either act to promote or prevent foam stability. The increase in stability is caused by the congenial incorporation of the smaller and more hydrophilic counterions such as tetraethyl ammonium cations and to some extent tetrabutyl ammonium cations into the interfacial anionic layers. This causes regular thin film drainage rates and promotes black films and stable foams. The structure changes increase the interfacial cohesive interaction and resiliency within the thin film lamella. The decrease in stability is associated with rapid drainage rates and is caused by the penetration of larger more hydrophobic tetrapentylammonium cations in the layers. This disrupts and weakens the molecular interactions (less cohesion). This result is quite different from previously reported studies (1) describing with the action of tetraalkylammonium counterions on sodium dodecyl sulphate (at concentrations above the cmc). At these higher surfactant concentrations, a defoaming action was generally observed and could be explained in terms of a reduction in the dynamic stability (Gibbs surface elasticity).

  • 145. Manev, ED
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Drainage and equilibrium thickness of aqueous films containing nonionic frothers and xanthate flotation collector1992Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 151, s. 505-516Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Drainage and stability of thin aqueous froth foam films from aqueous solutions of non-ionic flotation frothers (polyoxyethylene- and polyoxy-propylene-alkylethers) in the presence of xanthate flotation collector were studied. It was shown that the drainage pattern and the stability of the films produced from the different surfactants were comparable. Also the films were shown to be stabilized after initial drainage by electrostatic repulsion forces generated at the air/solution interface. The film charge could be modified by changes in concentration of frother and xanthate. Increasing concentration of xanthate decreased the cohesion in the surface layers and hence the froth stability.

  • 146.
    Millqvist-Fureby, A
    et al.
    YKI – Ytkemiska institutet.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    An aqueous polymer two-phase system as carrier in the spray-drying of biological material2000Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 225, s. 54-61Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This investigation describes a novel concept in formulation of carrier systems for spray-drying of biological materials. As carrier materials a system composed of poly (vinyl pyrrolidone) (PVP) and dextran was used. This system yields an aqueous two-phase system in which each phase is enriched in one of the polymers. By varying the composition of the system, the effective structure of a 'stirred' such system can be varied, covering the entire range from dextran continuous to PVP continuous. This facilitates encapsulation of either of these polymers in a spray-drying operation. In an attempt to investigate the spray-drying from such a system, the surface composition of the spray-dried powder obtained from various compositions of the two-phase system was analysed by electron spectroscopy for chemical analysis (ESCA), providing information on the distribution of the polymers in the powder and thus also in the spray droplets. The two-phase system was applied for spray-drying of live bacteria. The survival rate of the bacteria depended on the composition of the two-phase system. The storage stability of the bacteria in these formulations was investigated after storage at room temperature under dry conditions for four weeks, and it was found that the survival rate was 10-45%. The results therefore show that this type of formulation holds promise for future applications for micro-organisms as well as other sensitive biological materials such as proteins.

  • 147. Mollmann, SH
    et al.
    Bukrinsky, JT
    Frokjaer, S
    Elofsson, U
    YKI – Ytkemiska institutet.
    Adsorption of human insulin and AspB28 insulin on a PTFE-like surface2005Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 286, s. 28-35Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interactions of human insulin, Zn-free human insulin, and AspB28 insulin with a hydrophobic surface were studied by ellipsometry. All three insulin types investigated adsorbed with high affinity onto the hydrophobic surface, as the plateau of the adsorption isotherm, represented by the irreversible bound fraction, was reached at concentrations >10-3 mg/ml. The plateau values for human insulin and Zn-free human insulin could not be distinguished with statistical significance, whereas the plateau value for AspB28 insulin was lower than those for the two others, with an adsorbed amount corresponding to a monolayer of insulin monomers. The results observed may be explained by differences in self-association patterns of the insulin types or by enhanced charge repulsion between the AspB28 analog and the negatively charged surface

  • 148. Mueller, H
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Hellsten, M
    Investigations on the interaction between metal ions and alkyl phosphate monolayers at the air-water interface by means of surface pressure determination and infrared spectroscopy1970Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 32, s. 132-140Artikel i tidskrift (Refereegranskat)
  • 149. Muller, D
    et al.
    Carlsson, F
    Malmsten, M
    YKI – Ytkemiska institutet.
    Adsorption of poly(ethylene oxide)-poly(lactide) copolymers. Effects of composition and degradation2001Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 236, s. 116-126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of chemical degradation of two diblock copolymers of poly(ethylene oxide) (E) and poly(lactide) (L), E39L5 and E39L20, on their adsorption at silica and methylated silica was investigated with in situ ellipsometry. Steric stablization of polystyrene dispersions was investigated in relation to degradation. Hydrolysis of the poly(lactide) block of the copolymers was followed at different temperatures and pH by using HPLC to measure the occurrence of lactic acid in solution. The block copolymers were quite stable in pH-unadjusted solution at low temperature, whereas degradation was facilitated by increasing temperature or lowering of the pH. Lower degradation rates of E39L20 where observed at low temperature in comparison with those of E39L5, whereas the degradation rates of the copolymers were quantitatively similar at high temperature. The adsorption of the copolymers at methylated silica substrates decreased with increasing degree of degradation due to the reduction in the ability of hydrophobic block to anchor the copolymer layer at the surface. At silica the adsorption initially increased with increasing degradation, particularly for E39L20 due to deposition of aggregates onto the surface. After extensive degradation the adsorption of the copolymers at both silica and methylated silica resembled that of the corresponding poly(ethylene oxide) homopolymer. Overall, it was found that the eventual reduction in adsorption occurred at a lower degree of degradation for E39L5 than for E39L20. Mean-field calculations showed a reduced anchoring for the block copolymers with decreasing poly(lactide) block length at hydrophobic surfaces. In accordance with this finding, it was observed that polystyrene dispersions were stabilized by E39L20 or E39L5 in a way that depended on both the lactide block length and the degree of degradation. Upon degradation of the hydrophobic block, stabilization of the polystyrene dispersions was maintained initially, but eventually degradation resulted in destabilization. The average residual copolymer concentration required for stabilization of the polystyrene dispersions was much higher than the corresponding concentration of intact copolymer required for stabilization.

  • 150. Muller, D
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Tanodekaew, S
    Booth, C
    Adsorption of diblock copolymers of poly(ethylene oxide) and poly(lactide) at hydrophilic silica from aqueous solution2000Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 228, s. 317-325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of a series of amphiphilic poly(ethylene oxide)-poly(DL-lactide) (PEO-PL) diblock copolymers at the water/silica interface was investigated by ellipsometry and reflectometry. For all copolymers, a much higher saturation adsorption is found compared to that of the PEO homopolymers, indicating the importance of the PL block for the adsorption. The copolymers display a saturation adsorption that increases with increasing hydrophobic content of the polymer, and decreases with increasing hydrophilic content of the polymer. Despite this, however, the layer thickness observed is rather similar for all polymers, regardless of the length and composition of the copolymers. Moreover, the layer thicknesses were significantly higher than what would be expected for the unperturbered copolymer dimensions. The initial adsorption kinetics of the different copolymers are comparable. The initial adsorption rate increases cooperatively with concentration and is slower than that expected for diffusion-controlled adsorption. Moreover, the adsorption increases only slightly over a concentration the range from 20 to 50°C. Furthermore, pH titrations show that all polymers exhibit a critical desorption pH of 8-9, which is lower than the corresponding value of pH 10.5 observed for the PEO homopolymer. These results are discussed in terms of the adsorption mechanism and the adsorbed layer structure and formation.

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