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  • 1.
    Afifi, Hala
    et al.
    Institute of Pharmaceutical Science, King’s College London, UK.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Heenan, Richard K.
    ISIS-CCLRC, Rutherford Appleton Laboratory, Chilton, UK.
    Dreiss, Cécile A.
    Institute of Pharmaceutical Science, King’s College London, UK.
    Structural transitions in cholesterol-based wormlike micelles induced by encapsulating alkyl ester oils with varying architecture2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 378, no 1, p. 125-134Article in journal (Refereed)
    Abstract [en]

    The effect of encapsulating oils on the phase behaviour and the microstructure of wormlike micelles formed by polyoxyethylene cholesteryl ether (ChEO10) and triethylene glycol monododecyl ether co-surfactant (C12EO3) was investigated using rheology, Cryo-TEM and small-angle neutron scattering measurements. Six alkyl ester oils bearing small, systematic variations in their molecular structure were encapsulated: ethyl butyrate (EB24), ethyl caproate (ECO26), ethyl caprylate (EC28), methyl enanthate (ME17), methyl caprylate (MC18) and butyl butyrate (BB44), where the subscripts refer to the length of the alkyl chain and fatty acid chain, respectively, on either sides of the ester link. The addition of alkyl ester oils to ChEO10/C12EO3 solutions promotes the longitudinal growth of the surfactant aggregates into wormlike micelles possessing an elliptical cross-section, with rminor 31 Â± 2 Ã… and rmajor varying from 45 to 70 Ã…. At fixed alkyl chain length, oils with longer fatty acid chains were found to be more efficient in inducing wormlike micelle formation or their elongation, following the order: EC28 > ECO26 > EB24. Instead, at fixed fatty acid chain length, increasing the alkyl chain has a negative effect on the longitudinal micellar growth (MC18 > EC28 and EB24 > BB44). At high co-surfactant concentrations and in the presence of EB24, an unusual phase of ring-like micelles was detected. Overall, the orientation of the oil molecules within the micelles enables them to act as co-surfactants with a small head-group, decreasing the average cross-section area and promoting longitudinal growth of the micelles into worms.

  • 2.
    Bergkvist, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Surface Biotechnology.
    Carlsson, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Surface Biotechnology.
    Karlsson, Torbjörn
    Oscarsson, Sven
    TM-AFM Threshold Analysis of Macromolecular Orientation: A Study of the Orientation of IgG and IgE on Mica Surfaces1998In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 206, no 2, p. 475-481Article in journal (Refereed)
    Abstract [en]

    Adsorption and orientation properties of two different types of immunoglobulin molecules on derivatized and native mica surfaces were investigated using TM-AFM. The analyses included height measurements at two different pH values and a new technique, presented here as threshold analysis, which displays the outer mantle shape of an adsorbed protein. A major difference in preferential orientation is observed upon comparing the adsorption of the two proteins onto the different surfaces. The characteristics of both the adsorbed immunoglobulin and the surface are important for any preferential orientation of the adsorbed protein.

  • 3. Bergström, L Magnus
    et al.
    Bramer, Tobias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Synergistic effects in mixtures of oppositely charged surfactants as calculated from the Poisson-Boltzmann theory: A comparison between theoretical predictions and experiments2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 322, no 2, p. 589-595Article in journal (Refereed)
    Abstract [en]

    Critical micelle concentrations in mixtures of an anionic surfactant and a cationic amphiphilic drug have been investigated using a model-independent procedure to quantify observed synergistic effects. Experimental results were compared with a theory based on the Poisson-Boltzmann mean field approximation of a charged interface with a diffuse layer of counterions. Explicit expressions for the activity coefficients from which the critical micelle concentration can be calculated and quantitatively predicted have been derived and excellent agreement between experimental data and theory was obtained. As a result, we demonstrate that it is possible to rationalize and predict the magnitude of synergism in mixtures of oppositely charged surfactants in the presence of added salt.

  • 4.
    Berts, Ida
    et al.
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry. Inst Laue Langevin, 71 Ave Martyrs,CS 20156, F-38042 Grenoble, France..
    Fragneto, Giovanna
    Inst Laue Langevin, 71 Ave Martyrs,CS 20156, F-38042 Grenoble, France..
    Porcar, Lionel
    Inst Laue Langevin, 71 Ave Martyrs,CS 20156, F-38042 Grenoble, France..
    Hellsing, Maja S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala Univ, Ctr Neutron Scattering, Box 516, S-75120 Uppsala, Sweden..
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala Univ, Ctr Neutron Scattering, Box 516, S-75120 Uppsala, Sweden..
    Controlling adsorption of albumin with hyaluronan on silica surfaces and sulfonated latex particles2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 504, p. 315-324Article in journal (Refereed)
    Abstract [en]

    Polysaccharides are known to modify binding of proteins at interfaces and this paper describes studies of these interactions and how they are modified by pH. Specifically, the adsorption of human serum albumin on to polystyrene latex and to silica is described, focusing on how this is affected by hyaluronan. Experiments were designed to test how such binding might be modified under relevant physiological conditions. Changes in adsorption of albumin alone and the co-adsorption of albumin and hyaluronan are driven by electrostatic interactions. Multilayer binding is found to be regulated by the pH of the solution and the molecular mass and concentration of hyaluronan. Highest adsorption was observed at pH below 4.8 and for low molecular mass hyaluronan (<= 150 kDa) at concentrations above 2 mg ml(-1). On silica with grafted hyaluronan, albumin absorption is reversed by changes in solvent pH due to their strong electrostatic attraction. Albumin physisorbed on silica surfaces is also rinsed away with dilute hyaluronan solution at pH 4.8. The results demonstrate that the protein adsorption can be controlled both by changes of pH and by interaction with other biological macromolecules.

  • 5. Boge, Lukas
    et al.
    Västberg, Amanda
    Umerska, Anita
    Bysell, Helena
    Eriksson, Jonny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Millqvist-Fureby, Anna
    Andersson, Martin
    Freeze-dried and re-hydrated liquid crystalline nanoparticles stabilized with disaccharides for drug-delivery of the plectasin derivative AP114 antimicrobial peptide2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 522, p. 126-135Article in journal (Refereed)
    Abstract [en]

    Liquid crystalline nanoparticles (LCNPs), e.g. cubosomes and hexosomes, are receiving more and more attraction as drug delivery vehicles. Dry powder formulation that forms LCNPs upon hydration can be advantageous to make new routes of administration accessible. In this work, we investigate use of three disaccharides (lactose, trehalose and sucrose) as protective matrices for glycerol monooleate based LCNP forming powders produced by freeze-drying. Phase behavior, particle size and size distributions at the different preparation steps were monitored by small angle x-ray scattering (SAXS) and dynamic light scattering (DLS). Particle appearance was imaged by cryogenic transmission electron microscopy (cryo-TEM). Moreover, the therapeutic relevant antimicrobial peptide AP114 (plectasin derivative) was incorporated in the formulations. Peptide encapsulation and release as well as in vitro antibacterial effect were investigated. Results showed that all freeze-dried powders did form particles with liquid crystalline structure upon hydration. However, a phase transition from the bicontinuous cubic Pn3m to the reversed hexagonal was observed, as a consequence of sugar addition and the freeze-drying procedure. Data indicates that trehalose is the preferred choice of lyo-protectant in order to maintain a mono-modal particle size distribution. In addition, antimicrobial activity of AP114-containing formulations was found to be highest for the formulation containing trehalose. The release kinetics of AP114 from the nanoparticles was strongly affected by the dimensions of the hexagonal phase. Larger dimension of the hexagonal phase, significantly improved the release of AP114 and antimicrobial activity of the formulation.

  • 6.
    Borro, Bruno C.
    et al.
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Bohr, Adam
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Bucciarelli, Saskia
    Univ Copenhagen, Dept Drug Design & Pharmacol, Jagtvej 162, DK-2100 Copenhagen, Denmark.
    Boetker, Johan P.
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Foged, Camilla
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Rantanen, Jukka
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Microfluidics-based self-assembly of peptide-loaded microgels: Effect of three dimensional (3D) printed micromixer design2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 538, p. 559-568Article in journal (Refereed)
    Abstract [en]

    In an effort to contribute to research in scalable production systems for polymeric delivery systems loaded with antimicrobial peptides (AMPS), we here investigate effects of hydrodynamic flow conditions on microfluidic particle generation. For this purpose, rapid prototyping using 3D printing was applied to prepare micromixers with three different geometric designs, which were used to prepare Ca2+-crosslinked alginate microgels loaded with the AMP polymyxin B in a continuous process. Based on fluid dynamic simulations, the hydrodynamic flow patterns in the micromixers were designed to be either (i) turbulent with chaotic disruption, (ii) laminar with convective mixing, or (iii) convective with microvortex formation. The physicochemical properties of the microgels prepared with these micromixers were characterized by photon correlation spectroscopy, laser-Doppler micro-electrophoresis, smallangle x-ray scattering, and ellipsometry. The particle size and compactness were found to depend on the micromixer geometry: From such studies, particle size and compactness were found to depend on micromixer geometry, the smallest and most compact particles were obtained by preparation involving microvortex flows, while larger and more diffuse microgels were formed upon laminar mixing. Polymyxin B was found to be localized in the particle interior and to cause particle growth with increasing peptide loading. Ca2+-induced cross-linking of alginate, in turn, results in particle contraction. The peptide encapsulation efficiency was found to be higher than 80% for all investigated micromixer designs; the highest encapsulation efficiency observed for the smallest particles generated by microvortexmediated self-assembly. Ellipsometry results for surface-immobilized microgels, as well as results on peptide encapsulation, demonstrated electrolyte-induced peptide release. Taken together, these findings demonstrate that rapid prototyping of microfluidics using 3D-printed micromixers offers promises for continuous manufacturing of AMP-loaded microgels. Although the micromixer combining turbulent flow and microvortexes was demonstrated to be the most efficient, all three micromixer designs were found to mediate self-assembly of small microgels displaying efficient peptide encapsulation. This demonstrates the robustness of employing 3D-printed micromixers for microfluidic assembly of AMP-loaded microgels during continuous production. 

  • 7.
    Braun, Katharina
    et al.
    Univ Ulm, Dept Inorgan Chem 2, D-89031 Ulm, Germany..
    Pochert, Alexander
    Univ Ulm, Dept Inorgan Chem 2, D-89031 Ulm, Germany..
    Linden, Mika
    Univ Ulm, Dept Inorgan Chem 2, D-89031 Ulm, Germany..
    Davoudi, Mina
    Lund Univ, Dept Clin Sci, Div Dermatol & Venereol, SE-22184 Lund, Sweden..
    Schmidtchen, Artur
    Lund Univ, Dept Clin Sci, Div Dermatol & Venereol, SE-22184 Lund, Sweden.;Nanyang Technol Univ, Lee Kong Chian Sch Med, 11 Mandalay Rd, Singapore 308232, Singapore..
    Nordström, Randi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Membrane interactions of mesoporous silica nanoparticles as carriers of antimicrobial peptides2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 475, p. 161-170Article in journal (Refereed)
    Abstract [en]

    Membrane interactions are critical for the successful use of mesoporous silica nanoparticles as delivery systems for antimicrobial peptides (AMPs). In order to elucidate these, we here investigate effects of nanoparticle charge and porosity on AMP loading and release, as well as consequences of this for membrane interactions and antimicrobial effects. Anionic mesoporous silica particles were found to incorporate considerable amounts of the cationic AMP LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES (LL-37), whereas loading is much lower for non-porous or positively charged silica nanoparticles. Due to preferential pore localization, anionic mesoporous particles, but not the other particles, protect LL-37 from degradation by infection-related proteases. For anionic mesoporous nanoparticles, membrane disruption is mediated almost exclusively by peptide release. In contrast, non-porous silica particles build up a resilient LL-37 surface coating due to their higher negative surface charge, and display largely particle-mediated membrane interactions and antimicrobial effects. For positively charged mesoporous silica nanoparticles, LL-37 incorporation promotes the membrane binding and disruption displayed by the particles in the absence of peptide, but also causes toxicity against human erythrocytes. Thus, the use of mesoporous silica nanoparticles as AMP delivery systems requires consideration of membrane interactions and selectivity of both free peptide and the peptide-loaded nanoparticles, the latter critically dependent on nanoparticle properties.

  • 8. Burks, T
    et al.
    Avila, M
    Akhtar, F
    Gothelid, M
    Lansåker, Pia C
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Toprak, M S
    Muhammed, M
    Uheida, A
    Studies on the adsorption of chromium(VI) onto 3-Mercaptopropionic acid coated superparamagnetic iron oxide nanoparticles2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 425, p. 36-43Article in journal (Refereed)
    Abstract [en]

    Chromium (Cr) in the form of Cr(VI) is deemed toxic in water due to its mutagenic and carcinogenic properties. For the successful removal of Cr(VI), we demonstrate a novel adsorbent consisting of superparamagnetic iron oxide nanoparticles (SPION) functionalized with 3-Mercaptopropionic acid (3-MPA). Fourier transform infrared spectroscopy (FT-IR) confirmed the functionalization of nanoparticles and presence of sulfonate groups. Batch adsorption experiments showed that the functionalized adsorbent recovered 45 mg of Cr(VI)/g of 3-MPA coated SPION at initial concentration of 50 mg/L aqueous solution at pH 1 with less than 1% of Fe dissolution from SPION. The results from X-ray photoelectron spectroscopy confirmed that Cr(VI) chemisorbed onto the adsorbent. Hence, the XPS spectra did not indicate any reduction of Cr(VI) to Cr(III) upon adsorption. The adsorption data were better fitted for the Freundlich model. Moreover, the Cr(VI) adsorption kinetics on functionalized SPION followed a pseudo-second order rate, revealing chemisorption as the dominant mechanism. The high Cr(VI) removal, rapid adsorption kinetics and stability of adsorbent indicate that 3-MPA coated SPION could be an efficient adsorbent for the removal of Cr(VI). (C) 2014 Elsevier Inc. All rights reserved.

  • 9.
    Bysell, Helena
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Hansson, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Transport of poly-L-lysine into oppositely charged poly(acrylic acid) microgels and its effect on gel deswelling.2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 323, no 1, p. 60-9Article in journal (Refereed)
    Abstract [en]

    The interaction between poly-L-lysine (pLys) and oppositely charged poly(acrylic acid) (pAA) microgels (Ø approximately 80-120 microm) was studied by micromanipulator-assisted light microscopy and confocal laser scanning microscopy. The aim of this study was to investigate effects of peptide size, pH, and salt concentration on binding, transport, and distribution of pLys in pAA microgel particles and thereby also to outline the details of the gel deswelling in response to pLys binding and incorporation. Both peptide distribution and gel deswelling kinetics were found to be strongly influenced by the pLys molecular weight, originating partly from limited entry of large peptides into the gel particle core. Also pH was shown to influence both deswelling and pLys incorporation kinetics, with a decreased deswelling rate observed with increasing pH. These effects are determined by a complex interplay between the pH-dependence of both pLys and the gel network, also influencing volume transitions of the latter. Finally, salt concentration was shown to have a significant effect on both gel deswelling rate and pLys transport, with an increased electrolyte concentration resulting in decreased deswelling rate but also in an increased peptide transport rate within the microgel particles.

  • 10.
    Cui, Zhong-Kai
    et al.
    Department of Chemistry, Centre for Self-Assembled Chemical Structures (CSACS), Université de Montréal, Canada.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Orellana, Alejandro Nieto
    INSERM U1066, Micro et Nanomédecines Biomimétiques-MINT, France AND LUNAM Université, UMR-S1066, Angers F-49933, France.
    Bastiat, Guillaume
    INSERM U1066, Micro et Nanomédecines Biomimétiques-MINT, France AND LUNAM Université, UMR-S1066, Angers F-49933, France.
    Benoit, Jean-Pierre
    INSERM U1066, Micro et Nanomédecines Biomimétiques-MINT, France AND LUNAM Université, UMR-S1066, Angers F-49933, France.
    Lafleur, Michel
    Department of Chemistry, Centre for Self-Assembled Chemical Structures (CSACS), Université de Montréal, Canada.
    Impact of interfacial cholesterol-anchored polyethylene glycol on sterol-rich non-phospholipid liposomes2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 428, p. 111-120Article in journal (Refereed)
    Abstract [en]

    Hypothesis

    Liposomes made of single-chain amphiphiles and a large amount of sterols display several advantages including a limited permeability. In the present paper, we examine the possibility to prepare such non-phospholipid liposomes with interfacial polyethylene glycol (PEG) in order to improve their circulation in the blood stream. Cholesterol (Chol) was chosen as the PEG anchor.

    Experiments

    The phase behavior of mixtures of palmitic acid (PA) and cholesterol including various proportions of PEGylated cholesterol (PEG-Chol) was characterized. In conditions leading to the formation of fluid bilayers, properties of the resulting liposomes were assessed.

    Findings

    Up to 20 mol% of PEGylated cholesterol could be introduced without significant perturbations in fluid bilayers made of PA and cholesterol. With 10 mol% PEG-Chol, PA/Chol/PEG-Chol liposomes showed a very limited permeability to calcein and doxorubicin. Doxorubicin could be actively loaded in PA/Chol/PEG-Chol liposomes with a high drug loading efficiency and a high drug to lipid ratio. Pharmaco-kinetic experiments in rats indicated that interfacial PEG reduced the clearance of PA/Chol liposomes compared to the naked ones. However the lifetime of these non-phospholipid liposomes in the blood circulation was considerably shorter than that observed for control PEGylated phospholipid liposomes, a phenomenon associated with the negative interfacial charge of the PA/Chol/PEG-Chol liposomes. 

  • 11.
    Dew, Noel
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Bramer, Tobias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Edsman, Katarina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Catanionic aggregates formed from drugs and lauric or capric acids enable prolonged release from gels2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 323, no 2, p. 386-394Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to add to the range of charged surfactants that can be used to form catanionic aggregates with oppositely charged surface active drug substances, and to apply these aggregates to prolong drug release from gels. The surfactants used in this study, lauric and capric acids are of natural origin-unlike traditionally used, synthetic, surfactants. The mixtures of drug substances and oppositely charged surfactants were studied visually and with cryogenic transmission electron microscopy. Drug release from gels was studied with a modified USP paddle method. This study shows that lauric and capric acids are as, or even more, active in forming catanionic aggregates than traditionally used surfactants such as sodium dodecyl sulfate. It is shown that the length of the hydrophobic part of the surfactant plays an important role in the formation of pharmaceutically interesting catanionic aggregates. As seen in previous studies, using catanionic vesicles prolongs the drug release from gels and decreases the apparent diffusion coefficient by a factor of 10-50, compared to a gel containing only drug substance.

  • 12.
    Feiler, Adam A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Sahlholm, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Sandberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Caldwell, Karin D.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Adsorption and viscoelastic properties of fractionated mucin (BSM) and bovine serum albumin (BSA) studied with quartz crystal microbalance (QCM-D)2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 315, no 2, p. 475-481Article in journal (Refereed)
    Abstract [en]

    The adsorption profile and viscoelastic properties of bovine submaxillary gland mucin (BSM) and bovine serum albumin (BSA), extracted from a commercial mucin preparation, adsorbing to polystyrene surfaces has been studied using quartz crystal microbalance with dissipation monitoring (QCM-D). A significant difference in the adsorption properties of the different proteins was detected; with the BSA adsorbing in a flat rigid layer whilst the mucin adsorbed in a diffuse, highly viscoelastic layer. Subsequent addition of BSA to the preadsorbed mucin layer resulted in stiffening of the protein layer which was attributed to complexation of the mucin by BSA. In contrast, a preadsorbed layer of BSA prevented mucin adsorption altogether. Combined mixtures of mucin and BSA in well defined ratios revealed intermediate properties between the two separate protein species which varied systematically with the protein ratios. The results shed light on the synergistic effects of complexation of lower molecular weight biomolecular species with mucin. The possibility to selectively control protein uptake and tailor the physical properties of the adsorbed layer makes mucin an attractive option for application in biomaterial coatings.

  • 13. Francisco, Kelly R.
    et al.
    da Silva, Marcelo A.
    Sabadini, Edvaldo
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Dreiss, Cécile A.
    Effect of monomeric and polymeric co-solutes on cetyltrimethylammonium bromide wormlike micelles: Rheology, Cryo-TEM and Small-angle neutron scattering2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 345, no 2, p. 351-359Article in journal (Refereed)
    Abstract [en]

    The effect of hydrophobic and hydrophilic co-solutes on the theological properties of wormlike micelles of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) or sodium bromide (NaBr) was investigated. Monomeric (ethanol, 2-propanol, benzene and benzylic alcohol) and polymeric species (poly(ethylene oxide), poly(vinyl alcohol) and poly(propylene oxide), respectively PEO, PVA and PPO) of varying molecular weight were studied in order to assess the effect of co-solute 'length' on the interactions with the wormlike micelles. Rheological properties were characterised by the plateau modulus G(0) and the relaxation time tau(R) obtained from fits to the Maxwell model, and by the zero-shear viscosity eta(0). The rheological properties were unaltered by the addition of all hydrophilic solutes (up to 20 mM). With hydrophobic co-solutes instead, both eta(0) and tau(R) decreased considerably, while Go was unaffected. The effects were particularly remarkable with PPO for concentrations as low as 5 mM (ca. 0.3 g L-1), and tau(R) was seen to follow an exponential decrease with polymer M-w. The effect of the aromatic solutes (benzene and benzyl alcohol) on the rheology was highly dependent on the counterions used to induce micellar growth (Sal(-) or Br-), revealing a different type of interaction. Surprisingly, small-angle neutron scattering and Cryo-TEM measurements showed that the drastic changes observed in the rheology were not correlated to any visible structural change. Therefore the strong decrease in viscosity and relaxation time are to be attributed to other mechanisms than micellar break-up or rod-to-sphere transition.

  • 14.
    Hansson, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Phase behavior of aqueous polyion-surfactant ion complex salts: A theoretical analysis.2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 332, no 1, p. 183-193Article in journal (Refereed)
    Abstract [en]

    A simple thermodynamic theory is presented for water swollen complex salts formed by ionic surfactant and oppositely charged polyions. The description takes into account, on approximate level, free energy contributions from attractive and repulsive polyion-mediated interactions between the micelles, the mixing of micelles, polyion chains and water, and the hydrophobic effect. Explicit expressions for the chemical potentials of water, polyion, and surfactant ion are derived and used to calculate phase diagrams at various degrees of polymerization and linear charge density of the polyion and for surfactants with 12 and 16 carbons in the tail group. In all calculations the aggregation number is optimized and the phase structure (disordered or fcc) is determined. The effect of varying the charge densities of spheres interacting with a cross-linked polyion network is also investigated. Results from theory are compared with experimental and Monte Carlo simulation data reported in the literature.

  • 15.
    Johansson, Christian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Gernandt, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Bradley, Melanie
    School of Chemistry, University of Bristol, United Kingdom.
    Vincent, Brian
    School of Chemistry, University of Bristol, United Kingdom.
    Hansson, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Interaction between lysozyme and colloidal poly(NIPAM-co-AAc) microgels2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 347, no 2, p. 241-251Article in journal (Refereed)
    Abstract [en]

    The interaction between lysozyme and colloidal poly(NIPAM-co-acrylic acid) microgels is investigated in aqueous solutions at neutral pH. Lysozyme binding isotherms, obtained within the ionic strength range 10-220 mM, indicate that the maximum uptake at 10 mM is 2.4 g lysozyme per gram dry gel, and that the uptake capacity decreases with increasing ionic strength to approximately 0 at 220 mM. Swelling isotherms, obtained from photon correlation spectroscopy measurements, show that the binding is accompanied by a substantial deswelling of the microgels. The microgel suspension is stable up to a protein-to-polymer charge ratio in the microgels of about 0.6, largely independent of ionic strength, whereas flocculation/sedimentation occurs at higher charge ratios. The charge ratio 0.6 corresponds to a zeta-potential of about -6 mV, as obtained from measurements of electrophoretic mobility. Binding and swelling isotherms are analyzed in detail and compared with predictions of theoretical model calculations. The influence of protein-protein attraction is highlighted, as well as the interplay between electrostatic interactions and network elasticity.

  • 16.
    Johansson, Christian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Hansson, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Interaction between lysozyme and poly(acrylic acid) microgels2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 316, no 2, p. 350-359Article in journal (Refereed)
    Abstract [en]

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

  • 17.
    Kaden, Heike
    et al.
    Karlsruhe Institute of Technology.
    Königer, Franz
    Karlsruhe Institute of Technology.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Emmerich, Katja
    Karlsruhe Institute of Technology.
    Low-frequency dielectric properties of three bentonites at different adsorbed water states2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 411, p. 16-26Article in journal (Refereed)
    Abstract [en]

    Three bentonites of varying smectite content were investigated by dielectric spectroscopy in the frequency range 10(-4) to 10(6)Hz after storage at well-defined humidities. The identification of relaxation processes from complex permittivity measurements was difficult, since conductivity effects were superimposed on the underlying relaxations. Relaxation peaks revealed by the dissipation factor indicated the occurrence of interfacial processes between 10(2) and 10(6) Hz. The intensity of the polarization of the electrochemical double-layer at the clay-water interface was promoted by increasing water content and was shifted to higher frequencies the higher the water content in the bentonites. Below ∼1Hz, electrode polarization (EP) was shown to be a participating process with capacitance values ranging from 0.6(*)10(-3) to 7.3(*)10(-3)F due to the accumulated charges. An equivalent circuit model was introduced that successfully described the low-frequency dielectric behavior of bentonites at low moisture levels. An included series R-CPE connection was used to describe the double-layer relaxation. At water contents up to 17%, the bulk resistivity was mainly influenced by smectite content and cation exchange capacity, whereas at water contents of ⩾19%, interlayer occupation and hydration state became more important.

  • 18. Kakehashi, Rie
    et al.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Almgren, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Stomatosomes, blastula vesicles and bilayer disks: morphological richness of structures formed in dilute aqueous mixtures of a cationic and an anionic surfactant2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 331, no 2, p. 484-493Article in journal (Refereed)
    Abstract [en]

    Cryogenic transmission electron microscopy (cryoTEM) was used to study the structures formed in mixts. of sodium dodecylsulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) in dil. aq. solns. with 0-300 mM NaBr. The DTAB mole fraction, X, was in the range 0.2-0.4, limited at 25 DegC by pptn. of solid DTA-DS at X = 0.38 without salt to X = 0.25 at 300 mM NaBr. At a total surfactant concn. of 100 mM the samples sepd. into two liq. phases (the bottom phase birefringent) within a narrow (+-0.01 mol fraction units) compn. range. At the mid-point X varied from 0.32 without salt to 0.22 at 300 mM NaBr. Elemental anal. of C, S, O, and N in the sepd. phases of a sample with 100 mM NaBr and X = 0.26 showed the top phase to contain almost only SDS at a low concn., 14 mM, and the bottom phase 175 mM total surfactant, with X = 0.27 . Elemental anal. on samples without added salt gave erratic results, indicating problems in the phys. sepn. of the phases. The cryoTEM survey of the sepd. phases revealed similar problems. Without salt both phases showed similar structures, whereas the top phase in the sample with added salt was void of structures larger than small micelles. The cryoTEM survey revealed a variety of structures being simultaneously present in most samples. A general trend with increasing X was an evolution from globular micelles, over disks, bands, branched bands transforming into sparse webs, perforated bilayer structures, and finally smooth bilayers. Increasing salt and total surfactant concns. resulted in the emergence of structures with smaller mean curvature at lower X. Perforated bilayers were found in samples with 100 mM or less of added salt, and usually persisted to DTAB contents where ppts. appeared. The porous bilayers seemed to derive from sparse webs of band-like structures, and the hole size decreased with increasing X and salt concn. Two types of recurrent structures were noticed: blastula aggregates, seemingly an intermediate structure transforming crumpled bilayers into vesicles of similar size (diam. 400-500 ANG.), obsd. over a broad range of conditions, and at 100 mM total surfactant concn. and 50 mM added salt or more a type of regular disks with a diam. of 180 +- 30 ANG.

  • 19.
    Kwaambwa, Habauka M.
    et al.
    Polytech Namibia, Sch Hlth & Appl Sci, Windhoek, Namibia..
    Hellsing, Maja S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Barker, Robert
    Inst Laue Langevin, F-38042 Grenoble 9, France..
    Interaction of Moringa oleifera seed protein with a mineral surface and the influence of surfactants2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 448, p. 339-346Article in journal (Refereed)
    Abstract [en]

    The paper describes the adsorption of purified protein from seeds of Moringa olelfera to a sapphire interface and the effects of addition of the anionic surfactant sodium dodecylsulfate (SOS) and the cationic surfactant hexadecyltrimethylammonium bromide (CTAB). Neutron reflection was used to determine the structure and composition of interfacial layers adsorbed at the solid/solution interface. The maximum surface excess of protein was found to be about 5.3 mg m(-2). The protein does not desorb from the solid/liquid interface when rinsed with water. Addition of SDS increases the reflectivity indicating co-adsorption. It was observed that CTAB is able to remove the protein from the interface. The distinct differences to the behavior observed previously for the protein at the silica/water interface are identified. The adsorption of the protein to alumina in addition to other surfaces has shown why it is an effective flocculating agent for the range of impurities found in water supplies. The ability to tailor different surface layers in combination with various surfactants also offers the potential for adsorbed protein to be used in separation technologies.

  • 20.
    Kwaambwa, Habauka M.
    et al.
    Namibia Univ Sci & Technol, Fac Hlth & Appl Sci, Private Bag 13388,13 Starch St, Windhoek, Namibia..
    Hellsing, Maja S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wasbrough, Matthew J.
    NIST, Ctr Neutron Res, 100 Bur Dr,Stop 6102, Gaithersburg, MD 20899 USA.;Univ Delaware, Chem & Biomol Engn, 150 Acad St, Newark, DE 19716 USA..
    Bleuel, Markus
    NIST, Ctr Neutron Res, 100 Bur Dr,Stop 6102, Gaithersburg, MD 20899 USA..
    Rennie, A. R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Salt induced polystyrene latex flocs investigated by neutron scattering2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 505, p. 9-13Article in journal (Refereed)
    Abstract [en]

    Studies with a model system consisting of polystyrene latex particles showed that the protein from seeds of Moringa trees adsorbs to the surface and causes flocculation as unusually dense aggregates. In this study, electrolytes sodium chloride (NaCI), ferric chloride (FeCl3) and aluminium sulfate (Al-2(SO4)(3)) have been used to aggregate model polystyrene particles. The study augments previous work using neutron scattering on the flocculation of polystyrene latex with protein from seeds of Moringa trees that had indicated higher floc dimension, df, values as the concentration of particles increased. The measurements were made using ultra small-angle neutron scattering. Generally the fractal dimension, and thus the floc density, increased with particle concentration and salt concentration. Flocculation was apparent at much lower concentrations of FeCl3 and Al-2(SO4)(3) than of NaCI. The values of df were found not to simply scale with ionic strength for the three electrolytes studied with FeCl3 being the most effective flocculating agent.

  • 21.
    Leroy, Philippe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. French Geol Survey, BRGM, F-45060 Orleans, France.
    Weigand, Maximilian
    Univ Bonn, Steinmann Inst, Dept Geophys, D-53115 Bonn, Germany..
    Meriguet, Guillaume
    Pierre & Marie Curie Univ, PHENIX, CNRS, UMR 8234, F-75252 Paris, France..
    Zimmermann, Egon
    Forschungszentrum Julich, Cent Inst Engn Elect & Analyt, Elect Syst, ZEA 2, D-52425 Julich, Germany..
    Tournassat, Christophe
    Univ Orleans, CNRS INSU BRGM, UMR 7327, Inst Sci Terre Orleans, F-45071 Orleans, France..
    Fagerlund, Fritjof
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Kemna, Andreas
    Univ Bonn, Steinmann Inst, Dept Geophys, D-53115 Bonn, Germany..
    Huisman, Johan Alexander
    Forschungszentrum Julich, Inst Bio & Geosci, IBG 3, Agrosphere Inst, D-52425 Julich, Germany..
    Spectral induced polarization of Na-montmorillonite dispersions2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 505, p. 1093-1110Article in journal (Refereed)
    Abstract [en]

    Montmorillonite (Mt) clays have a high specific surface area and surface charge, which confer them remarkable adsorption properties. Nevertheless, their electrochemical and aggregation behavior are not completely elucidated because of the complexity of their microstructural and interfacial properties. In this work, the conductive and dispersive properties of Na-Mt suspensions of weight fractions 0.5-5.2% were investigated for the first time using the spectral induced polarization method. A four-electrode system was used to reduce errors introduced by electrode polarization and contact resistances. Complex conductivity spectra in the low-frequency range of 0.1 Hz to 45 kHz were successfully described using a triple layer model of the basal surface of Mt and a complex conductivity model that considers conduction of the diffuse layer and polarization of the Stern layer. Aggregate size distributions were inferred from inverted relaxation time distributions. We found that the negative and permanent surface charge of the basal plane of Na-Mt controls its quadrature (imaginary) conductivity, which is not very sensitive to pH and salinity (NaCI) in the 100 Hz to 45 kHz frequency range. For lower frequencies, the sudden increase of the quadrature conductivity at the highest salinities was explained by considering coagulation of Na-Mt particles.

  • 22.
    Li, Ning Ning
    et al.
    Univ Oxford, Dept Chem, Phys & Theoret Chem Lab, S Parks Rd, Oxford OX1 3QZ, England..
    Thomas, Robert K.
    Univ Oxford, Dept Chem, Phys & Theoret Chem Lab, S Parks Rd, Oxford OX1 3QZ, England..
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Neutron reflectometry of anionic surfactants on sapphire: A strong maximum in the adsorption near the critical micelle concentration2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 471, p. 81-88Article in journal (Refereed)
    Abstract [en]

    The adsorption of the anionic surfactants, lithium, sodium and cesium dodecylsulfates, and sodium decylsulfonate, on the positively charged C-plane (0001) of sapphire (alumina) has been measured using neutron reflection. For each of the four surfactants there is a strong maximum in the adsorption at about the critical micelle concentration. The maximum becomes more marked from lithium to cesium. The measurements were reproduced over a range of different physical conditions and could not be accounted for in terms of impurities. The maximum is explained quantitatively by using the combination of a mass action model to calculate the mean activity of the surfactant, and a cooperative model of the adsorption (Frumkin), in which saturation of the layer is not attained until well above the critical micelle concentration.

  • 23. Li, Ningning
    et al.
    Thomas, Robert K.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Adsorption of non-ionic surfactants to the sapphire/solution interface: Effects of temperature and pH2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 369, p. 287-293Article in journal (Refereed)
    Abstract [en]

    The adsorption of the non-ionic surfactants tetraoxyethylene glycol monododecyl ether (C12EO4), pentaoxyethylene glycol monododecyl ether (C12EO5), and hexaoxyethylene glycol monododecyl ether (C12EO6) to single crystal sapphire substrates has been studied using specular neutron reflection for solutions at the critical micelle concentration. The effects of temperature and pH of the solutions were studied as well as the differences between two different crystal faces, the C and the R planes. At neutral pH, significant adsorption was only observed when the temperature was raised above the cloud temperature. This adsorption was reversible and surfactant was displaced on cooling. Reducing the pH to 3 results in significantly increased adsorption of C12EO5 at 25 degrees C with a central layer consisting mainly of surfactant (about 90%) on the C-plane substrate. A slightly smaller surface excess was observed for the R-plane. This contrasts with the significantly lower density observed even at high temperatures at neutral pH on both substrates. The results suggest that for neutral solutions surfactant association above the cloud point is the primary driving force for adsorption. At low pH, specific interactions with protonated surfaces are important. The structures of the highly hydrated layers are similar to those found for the surfactants at hydrophilic silica surfaces.

  • 24. Li, Ningning
    et al.
    Thomas, Robert K.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Effect of pH, surface charge and counter-ions on the adsorption of sodium dodecyl sulfate to the sapphire/solution interface2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 378, p. 152-158Article in journal (Refereed)
    Abstract [en]

    The role of ionic interactions between sodium dodecyl sulfate, SDS, and sapphire surfaces have been studied using specular neutron reflection to determine the structure and composition of adsorbed surfactant layers. Increasing the pH of the solution from 3 to 9 reduces the adsorption by reversing the charge of the alumina. This occurs at lower pH for the R-plane (1 (1) over bar 02) than the C-plane (0001), corresponding to the different points of zero charge. The largest surface excess is about 6.5 mu mol m(-2), the thickness of the adsorbed layer is about 24 angstrom and it contains roughly 20% water. The hydrocarbon tails of the surfactant molecules clearly interpenetrate rather than form an ordered bilayer. The structure is similar in either pure water or in 0.1 M NaCl when the surfactant is at the respective critical micelle concentration. Different structures were seen with lithium and cesium dodecyl sulfate. The CsDS forms dense layers with little or no hydration and a surface excess of about 10.5 mu mol m(-2). The metal cation strongly influences the hydration of the adsorbed surfactant. An overall picture of 'flattened micelles' for the structure of the adsorbed layer is observed.

  • 25. Lindfors, Lennart
    et al.
    Forssén, Sara
    Pharmaceutical and Analytical R&D, AstraZeneca R&D Mölndal, Sweden.
    Westergren, Jan
    Olsson, Ulf
    Department of Physical Chemistry, Lunds University.
    Nucleation and crystal growth in supersaturated solutions of a model drug2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 325, no 2, p. 404-413Article in journal (Refereed)
    Abstract [en]

    The crystallization process in aqueous solutions of the drug bicalutamide and the effect of the polymer polyvinylpyrrolidone (PVP) have been studied. Results show that PVP decreased the crystallization rate significantly in a system with PVP concentrations as low as 0.01% (w/w), without changing the polymorph formed. The crystal habit was changed already at PVP concentrations as low as 0.001% (w/w). Measurements made with self-diffusion NMR indicated that the decrease in crystallization rate was not because of a reduced supersaturation due to bicalutamide binding to PVP in solution. Furthermore, in experiments designed to specifically study crystal nucleation, the same nucleation rate was found in the absence and presence of PVP. Instead, PVP adsorbes to the crystals formed in solution and by doing so, the crystal growth rate is reduced. This was confirmed in separate experiments using bicalutamide nanocrystals. By combining theories describing classical nucleation and crystal growth, with some modifications, a consistent description of several independent experiments performed in polymer-free systems was obtained. From these experiments a crystal-water interfacial tension of 22.1 mN/m was extracted. We also analyze the interfacial tension of other crystalline organic solids and find that it varies approximately as the logarithm of the solubility. This finding is discussed within the framework of the Bragg-Williams regular solution theory where we also compare with the tension of liquid alkanes.

  • 26. Lopes, António
    et al.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Feitosa, Eloi
    Extruded vesicles of dioctadecyldimethylammonium bromide and chloride investigated by light scattering and cryogenic transmission electron microscopy2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 322, no 2, p. 582-588Article in journal (Refereed)
    Abstract [en]

    Combined dynamic and static light scattering (DLS, SLS) and cryogenic transmission electron microscopy (cryo-TEM) were used to investigate extruded cationic vesicles of dioctadecyldimethylammonium chloride and bromide (DODAX, X being Cl- or Br-). In salt-free dispersions the mean hydrodynamic diam., D h , and the wt. av. mol. wt., M w , are larger for DODAB than for DODAC vesicles, and both D h and M w increase with the diam. (f) of the extrusion filter. NaCl (NaBr) decreases (increases) the DODAB (DODAC) vesicle size, reflecting the general trend of DODAB to assemble as larger vesicles than DODAC. The polydispersity index is lower than 0.25, indicating the dispersions are rather polydisperse. Cryo-TEM micrographs show that the smaller vesicles are spherical while the larger ones are oblong or faceted, and the vesicle samples are fairly polydisperse in size and morphol. They also indicate that the vesicle size increases with f and DODAB assembles as larger vesicles than DODAC. Lens-shaped vesicles were obsd. in the extruded prepns. Both light scattering and cryo-TEM indicate that the vesicle size is larger or smaller than f when f is smaller or larger than the optimal f * ~ 200 nm .

  • 27. Lundin, Maria
    et al.
    Sandberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Caldwell, Karin D.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Blomberg, Eva
    Comparison of the adsorption kinetics and surface arrangement of "as received" and purified bovine submaxillary gland mucin (BSM) on hydrophilic surfaces2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 336, no 1, p. 30-39Article in journal (Refereed)
    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 A) layer upon applying a high load. "As received" BSM formed considerably thicker Compressed layers (35 A); 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. (C) 2009 Elsevier Inc. All rights reserved.

  • 28.
    Malmsten, Martin
    et al.
    Institute for Surface Chemistry.
    Lassen, Bo
    Institute for Surface Chemistry.
    Westin, Jerker
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Biomedical Informatics and Engineering.
    Gölander, C G
    Larsson, Rolf
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Clinical Immunology.
    Nilsson, Ulf R
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Clinical Immunology.
    Adsorption of complement protein C3 at polymer surfaces and the demonstration of a specific binding of factor B by adsorbed C31996In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 179, no 1, p. 163-172Article in journal (Refereed)
    Abstract [en]

    The adsorption of C3 at poly(methyl methacrylate) (PMMA) and poly(styrene) (PS) surfaces was investigated within situellipsometry 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 among 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.

  • 29.
    Milani, Silvia
    et al.
    Department of Chemistry and CSGI, University of Florence, Italy.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Baglioni, Piero
    Department of Chemistry and CSGI, University of Florence, Italy.
    Berti, Debora
    Department of Chemistry and CSGI, University of Florence, Italy.
    Association of polynucleotides with nucleolipid bilayers driven by molecular recognition2011In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 363, no 1, p. 232-240Article in journal (Refereed)
    Abstract [en]

    This contribution reports on the interaction of ss-polynucleotides of various length and sequence with liposomal dispersions of anionic lipids. No appreciable structural and morphological variations were detected for POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-glycerol) liposomes, as expected from the high negative charge density both of liposomal surface and of the poly or oligonucleotide. Conversely, when similarly charged POPN nucleolipids (1-palmitoyl-2-oleoylphosphatidyl-nucleosides) were used, meaningful differences could be observed both on size and morphology of the mixed aggregates. The comparison with POPG/nucleic acids mixed systems points to the conclusion that the driving force for association of nucleolipid liposomes with nucleic acids can be ascribed to selective interactions at the polar head level which overcome electrostatic repulsion. Dynamic light scattering, Cryo-TEM and circular dichroism provided an ensemble of results where an interesting dependence on the polynucleotide base nature and contour length emerges. The extent of interaction can be modulated, in terms of size of the complexes, by choice of background buffer, ionic strength and polynucleotide length.

  • 30.
    Morin Zetterberg, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Ahlgren, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Parveen, Nagma
    Chalmers, Biol Phys Div, Dept Phys, SE-41296 Gothenburg, Sweden.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Optimization of Lipodisk Properties by Modification of the Extent and Density of the PEG Corona2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 484, p. 86-96Article in journal (Refereed)
    Abstract [en]

    Lipodisks are nanosized flat, circular, phospholipid bilayers that are edge-stabilized by polyethylene glycol-conjugated lipids (PEG-lipids). Over the last decade, lipodisks stabilized with PEG of molecular weight 2000 or 5000 have been shown to hold high potential as both biomimetic membranes and drug carriers. In this study we investigate the possibilities to optimize the properties of the lipodisks, and widen their applicability, by reducing the PEG molecular weight and/or the density of the PEG corona. Results obtained by cryo-transmission electron microscopy and dynamic light scattering show that stable, well-defined lipodisks can be produced from mixtures of distearoylphosphatidylcholine (DSPC) and distearoylphosphatidylethanolamine conjugated to PEG of molecular weight 1000 (DSPE-PEG(1000)). Preparations based on the use of DSPE-PEG(750) tend, in contrast, to be polydisperse in size and structure. By comparing immobilization of lipodisks stabilized with DSPE-PEG(1000), DSPE-PEG(2000), and DSPE-PEG(5000) to porous and smooth silica surfaces, we show that the amount of surface bound disks can be considerably improved by the use of PEG-lipids with reduced molecular weight. Further, a modified preparation protocol that enables production of lipodisks with very low PEG-lipid content is described. The reduced PEG density, which facilitates the incorporation of externally added ligand-linked PEG-lipids, is shown to be beneficial for the production of targeting lipodisks.

  • 31.
    Moulin, M.
    et al.
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble 9, France;Keele Univ, Fac Nat Sci, Keele ST5 5BG, Staffs, England.
    Mossou, E.
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble 9, France;Keele Univ, Fac Nat Sci, Keele ST5 5BG, Staffs, England.
    Signor, L.
    Univ Grenoble Alpes, CNRS, CEA, IBS, F-38000 Grenoble, France.
    Kieffer-Jaquinod, S.
    Univ Grenoble Alpes, INSERM, CEA, BGE, F-38000 Grenoble, France.
    Kwaambwa, H. M.
    Namibia Univ Sci & Technol, Fac Hlth & Appl Sci, Private Bag 13388,13 Jackson Kaujeua St, Windhoek, Namibia.
    Nermark, F.
    Univ Botswana, Dept Chem, Private Bag UB00704, Gaborone, Botswana.
    Gutfreund, P.
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble 9, France.
    Mitchell, E. P.
    Keele Univ, Fac Nat Sci, Keele ST5 5BG, Staffs, England;European Synchrotron Radiat Facil, 71 Ave Martyrs, F-38043 Grenoble 9, France.
    Haertlein, M.
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble 9, France.
    Forsyth, V. T.
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble 9, France;Keele Univ, Fac Nat Sci, Keele ST5 5BG, Staffs, England.
    Rennie, Adrian Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Towards a molecular understanding of the water purification properties of Moringa seed proteins2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 554, p. 296-304Article in journal (Refereed)
    Abstract [en]

    Seed extracts from Moringa oleifera are of wide interest for use in water purification where they can play an important role in flocculation; they also have potential as anti-microbial agents. Previous work has focused on the crude protein extract. Here we describe the detailed biophysical characterization of individual proteins from these seeds. The results provide new insights relating to the active compounds involved. One fraction, designated Mo-CBP3, has been characterized at a molecular level using a range of biochemical and biophysical techniques including liquid chromatography, X-ray diffraction, mass spectrometry, and neutron reflection. The interfacial behavior is of particular interest in considering water purification applications and interactions with both charged (e.g. silica) and uncharged (alumina) surfaces were studied. The reflection studies show that, in marked contrast to the crude extract, only a single layer of the purified Mo-CBP3 binds to a silica interface and that there is no binding to an alumina interface. These observations are consistent with the crystallographic structure of Mo-CBP3-4, which is one of the main isoforms of the Mo-CBP3 fraction. The results are put in context of previous studies of the properties of the crude extract. This work shows possible routes to development of separation processes that would be based on the specific properties of individual proteins.

  • 32. Mäkie, Peter
    et al.
    Persson, Per
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Adsorption of trimethyl phosphate and triethyl phosphate on dry and water pre-covered hematite, maghemite, and goethite nanoparticles2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 392, p. 349-358Article in journal (Refereed)
    Abstract [en]

    Adsorption of trimethyl phosphate (TMP) and triethyl phosphate (TEP) on well-characterized nanoparticles of hematite (α-Fe2O3), maghemite (γ-Fe2O3), and goethite (α-FeOOH) has been studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), 2D correlation DRIFTS analysis, and X-ray photoelectron spectroscopy (XPS) on dry and water pre-covered surfaces. It is shown that, at room temperature and low coverage, both TMP and TEP coordinate to Lewis acid Fe sites through the O phosphoryl atom on hematite and maghemite, while hydrogen bonding to Brønstedt acid surface OH groups dominates on goethite. At room temperature, slow dissociation of TMP occurs on the iron (hydr)oxide nanoparticles, whereby a methoxy group is displaced to form surface methoxy, leaving adsorbed dimethyl phosphate (DMP). Methoxy is further decomposed to formate, suggesting an oxidative degradation pathway in synthetic air on the oxide particles. Relatively, larger amounts of DMP and surface methoxy form on maghemite, while more formate is produced on hematite. Upon TMP adsorption on dry goethite nanoparticles, no oxidation surface products were detected. Instead, a slow TMP hydrolysis pathway is observed, yielding orthophosphate. It is found that pre-adsorbed water stimulates the hydrolysis of TMP. In contrast to TMP, TEP adsorbs molecularly on all iron hydr(oxide) nanoparticles. This is attributed to the longer aliphatic chain, which stabilizes the loss of charge on the methoxy CO bonds by charge redistribution upon phosphoryl O coordination to Fe surface atoms. The presented results implicate different reactivity depending on specific molecular structure of the organophosphorus compound (larger functional groups can compensate loss of charge due to surface coordination) and iron (hydr)oxide surface structure (exposing Lewis acid or Brønstedt acid sites).

  • 33.
    Nilsson, Peter
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Hansson, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Regular and Irregular Deswelling of Polyacrylate and Hyaluronate Gels Induced by Oppositely Charged Surfactants2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 325, no 2, p. 316-323Article in journal (Refereed)
    Abstract [en]

    The deswelling kinetics of macroscopic polyacrylate (PA) gels in solutions of dodecyltrimethylammonium bromide (C(12)TAB) and cetyltrimethylammonium bromide (C(16)TAB), with and without added sodium bromide, as well as hyaluronate (HA) gels in solutions of cetylpyridinium chloride (CPC) are investigated. Additional data are also provided by small-angle X-ray scattering and microgel experiments. The purpose is to study the deswelling behavior of (1) regularly deswelling gels, for which the deswelling is successfully described using a core/shell model earlier employed for microgels, and (2) irregularly deswelling gels, where the gel turns into a balloon-like structure with a dense outer layer surrounding a liquid-filled core. For regularly deswelling gets, the deswelling of PA/C(12)TAB is found to be controlled by diffusion through both stagnant layer and collapsed surface phase, while for PA/C(16)TAB it is found to be controlled mainly by the latter. The difference in deswelling rate between the two is found to correspond to the difference in surfactant diffusion coefficient in the surface phase. Factors found to promote irregular deswelling, described as balloon formation, are rapid surfactant binding, high bromide and surfactant concentration, longer surfactant chain length, and macroscopic gel size. Scattering data indicating a cubic structure for HA/CPC complexes are reported.

  • 34.
    Nordström, Randi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Andrén, Oliver C.J.
    Kungliga Tekniska Högskolan.
    Singh, Shalini
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Malkoch, Michael
    Kungliga Tekniska Högskolan.
    Davoudi, Mina
    Lunds universitet.
    Schmidtchen, Artur
    Lunds universitet; Köpenhamns universitet.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Department of Pharmacy, University of Copenhagen.
    Degradable dendritic nanogels as carriers for antimicrobial peptides2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 554, p. 592-602Article in journal (Refereed)
    Abstract [en]

    In the present study, we investigate degradable anionic dendritic nanogels (DNG) as carriers for antimicrobial peptides (AMPs). In such systems, the dendritic part contains carboxylic acid-based anionic binding sites for cationic AMPs, whereas linear poly(ethylene glycol) (PEG) chains form a shell for promotion of biological stealth. In order to clarify factors influencing membrane interactions of such systems, we here address effects of nanogel charge, cross-linking, and degradation on peptide loading/release, as well as consequences of these factors for lipid membrane interactions and antimicrobial effects. The DNGs were found to bind the AMPs LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES) and DPK-060 (GKHKNKGKKNGKHNGWKWWW). For the smaller DPK-060 peptide, loading was found to increase with increasing nanogel charge density. For the larger LL-37, on the other hand, peptide loading was largely insensitive to nanogel charge density. In line with this, results on the secondary structure, as well as on the absence of stabilization from proteolytic degradation by the nanogels, show that the larger LL-37 is unable to enter into the interior of the nanogels. While 40–60% nanogel degradation occurred over 10 days, promoted at high ionic strength and lower cross-linking density/higher anionic charge content, peptide release at physiological ionic strength was substantially faster, and membrane destabilization not relying on nanogel degradation. Ellipsometry and liposome leakage experiments showed both free peptide and peptide/DNG complexes to cause membrane destabilization, indicated also by antimicrobial activities being comparable for nanogel-bound and free peptide. Finally, the DNGs were demonstrated to display low toxicity towards erythrocytes even at peptide concentrations of 100 µM.

  • 35.
    Nordström, Randi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Nyström, Lina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Andren, Oliver C. J.
    Royal Inst Technol, Dept Fibre & Polymer Technol, SE-10044 Stockholm, Sweden..
    Malkoch, Michael
    Royal Inst Technol, Dept Fibre & Polymer Technol, SE-10044 Stockholm, Sweden..
    Umerska, Anita
    Univ Bretagne Loire, CNRS 6021, INSERM U1066, Univ Angers,MINT, Angers, France..
    Davoudi, Mina
    Lund Univ, Dept Clin Sci, Div Dermatol & Venereol, SE-22184 Lund, Sweden..
    Schmidtchen, Artur
    Lund Univ, Dept Clin Sci, Div Dermatol & Venereol, SE-22184 Lund, Sweden.;Nanyang Technol Univ, Lee Kong Chian Sch Med, 11 Mandalay Rd, Singapore 308232, Singapore..
    Malmsten, M
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Univ Copenhagen, Dept Pharm, DK-2100 Copenhagen, Denmark..
    Membrane interactions of microgels as carriers of antimicrobial peptides2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 513, p. 141-150Article in journal (Refereed)
    Abstract [en]

    Microgels are interesting as potential delivery systems for antimicrobial peptides. In order to elucidate membrane interactions of such systems, we here investigate effects of microgel charge density on antimicrobial peptide loading and release, as well as consequences of this for membrane interactions and antimicrobial effects, using ellipsometry, circular dichroism spectroscopy, nanoparticle tracking analysis, dynamic light scattering and z-potential measurements. Anionic poly(ethyl acrylate-co-methacrylic acid) microgels were found to incorporate considerable amounts of the cationic antimicrobial peptides LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES) and DPK-060 (GKHKNKGKKNGKHNGWKWWW) and to protect incorporated peptides from degradation by infection-related proteases at high microgel charge density. As a result of their net negative z-potential also at high peptide loading, neither empty nor peptide-loaded microgels adsorb at supported bacteria-mimicking membranes. Instead, membrane disruption is mediated almost exclusively by peptide release. Mirroring this, antimicrobial effects against several clinically relevant bacteria (methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa) were found to be promoted by factors facilitating peptide release, such as decreasing peptide length and decreasing microgel charge density. Microgels were further demonstrated to display low toxicity towards erythrocytes. Taken together, the results demonstrate some interesting opportunities for the use of microgels as delivery systems for antimicrobial peptides, but also highlight several key factors which need to be controlled for their successful use.

  • 36.
    Nouhi, Shirin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ahrens, Lutz
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU).
    Campos Pereira, Hugo
    Swedish University of Agricultural Sciences: Uppsala, Sweden.
    Hughes, Arwel
    Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, United Kingdom.
    Campana, Mario
    Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, United Kingdom.
    Gutfreund, Philipp
    Institut Laue–Langevin.
    Pálsson, Gunnar K.
    Institut Laue–Langevin.
    Vorobiev, Alexei
    Institut Laue–Langevin.
    Hellsing, Maja S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Interactions of perfluoroalkyl substances with a phospholipid bilayer studied by neutron reflectometry2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 511, p. 474-481Article in journal (Refereed)
    Abstract [en]

    The interactions between perfluoroalkyl substances (PFASs) and a phospholipid bilayer (1,2-dimyristoyl-sn-glycero-3-phosphocholine) were investigated at the molecular level using neutron reflectometry. Representative PFASs with different chain length and functional groups were selected in this study including: perfluorobutane sulfonate (PFBS), perfluorohexanoate (PFHxA), perfluorohexane sulfonate (PFHxS), perfluorononanoate (PFNA), perfluorooctane sulfonate (PFOS), and perfluorooctane sulfonamide (FOSA). All PFASs were found to interact with the bilayer by incorporation, indicating PFAS ability to accumulate once ingested or taken up by organisms. The interactions were observed to increase with chain length and vary with the functional group as SO2NH2" role="presentation">(FOSA) > SO2O&#x2212;" role="presentation">(PFOS) > COO(PFNA). The PFAS hydrophobicity, which is strongly correlated with perfluorocarbon chain length, was found to strongly influence the interactions. Longer chain PFASs showed higher tendency to penetrate into the bilayer compared to the short-chain compounds. The incorporated PFASs could for all substances but one (PFNA) be removed from the lipid membrane by gentle rinsing with water (2 mL min−1). Although short-chain PFASs have been suggested to be the potentially less bioaccumulative alternative, we found that in high enough concentrations they can also disturb the bilayer. The roughness and disorder of the bilayer was observed to increase as the concentration of PFASs increased (in particular for the high concentrations of short-chain substances i.e. PFHxA and PFBS), which can be an indication of aggregation of PFASs in the bilayer.

  • 37.
    Parra-Ortiz, Elisa
    et al.
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Browning, Kathryn L.
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Damgaard, Liv S. E.
    Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Nordström, Randi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Micciulla, Samantha
    Inst Laue Langevin, F-38000 Grenoble, France.
    Bucciarelli, Saskia
    Univ Copenhagen, Dept Drug Design & Pharmacol, DK-2100 Copenhagen, Denmark.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Univ Copenhagen, Dept Pharm, Univ Pk 2, DK-2100 Copenhagen, Denmark.
    Effects of oxidation on the physicochemical properties of polyunsaturated lipid membranes2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 538, p. 404-419Article in journal (Refereed)
    Abstract [en]

    The exposure of biological membranes to reactive oxygen species (ROS) plays an important role in many pathological conditions such as inflammation, infection, or sepsis. ROS also modulate signaling processes and produce markers for damaged tissue. Lipid peroxidation, mainly affecting polyunsaturated phospholipids, results in a complex mixture of oxidized products, which may dramatically alter membrane properties. Here, we have employed a set of biophysical and surface-chemical techniques, including neutron and X-ray scattering, to study the structural, compositional, and stability changes due to oxidative stress on phospholipid bilayers composed of lipids with different degrees of polyunsaturation. In doing so, we obtained real-time information about bilayer degradation under in situ UV exposure using neutron reflectometry. We present a set of interrelated physicochemical effects, including gradual increases in area per molecule, head group and acyl chain hydration, as well as bilayer thinning, lateral phase separation, and defect formation leading to content loss upon membrane oxidation. Such effects were observed to depend on the presence of polyunsaturated phospholipids in the lipid membrane, suggesting that these may also play a role in the complex oxidation processes occurring in cells.

  • 38.
    Paulsson, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Edsman, Katarina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Controlled Drug Release from Gels Using Lipophilic Interactions of Charged Substances with Surfactants and Polymers2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 248, no 1, p. 194-200Article in journal (Refereed)
    Abstract [en]

    The aim of this article was to study interactions between different gel forming polymers and amphiphilic drugs and surfactants with the intention of finding interactions that can be used for designing controlled release formulations. The release from gels was measured by detecting the UV-absorbance of drugs released from 6 mL gel into 250 mL release medium in a dissolution bath. The rheological behavior of gels was characterized using a controlled rate rheometer. The diffusion coefficient of alprenolol was 6.3 x 10(-6) cm(2)/s when formulated in a 1% poly(acrylic acid) gel (PAA) and 2.8 x 10(-6) cm(2)/s in a lipophilically modified gel (LM-PAA). The addition of alprenolol to 1% LM-PAA increased the elasticity, G', from 123 to 182 Pa. Increased gel strength was also observed for a number of other amphiphilic drugs. The addition of 1% Brij 58 to LM-PAA decreased the diffusion coefficient of alprenolol to 2.3 x 10(-6) cm(2)/s. It was possible to sustain the release of charged drugs with high log P by adding surfactant micelles. However, the effect was small and only useful for drugs with adequate lipophilicity. The interaction between LM-PAA and amphiphilic drugs could be seen using rheology and was used for designing controlled release gel formulations. In this way surfactants can be avoided, thus decreasing toxicity problems.

  • 39.
    Qazi, S. Junaid S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Dispersions of plate-like colloidal particles: Cubatic order?2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 348, no 1, p. 80-84Article in journal (Refereed)
    Abstract [en]

    Experimental evidence for the existence of 'cubatic' order in a colloidal dispersion of plate-like particles is presented. In a 'cubatic' phase, disk-like particles self-assemble with domains of a few parallel plates and the director tends to be orthogonal in adjacent domains. This phase has been predicted previously by computer simulation. The domains are approximately equiaxial and are predicted to exist only within a limited range of aspect ratios and volume fractions. This locally ordered structure cannot be identified readily using scattering techniques, since the patterns are expected to be similar to those of isotropic liquid phases. For this reason, we have used a real-space technique of cryo-transmission electron microscopy that directly probes such locally ordered structures to study dispersions of nickel hydroxide particles. Polydispersity of particle size is expected to require some local tilting in order to include larger particles in a dense structure and this is discussed with respect to the concentration range for which cubatic order is observed. This new structure offers the possibility of novel materials that could be prepared by self-assembly and have applications in a wide range of fields.

  • 40.
    Qazi, S. Junaid S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Cockcroft, K
    Vickers, Martin
    Use of wide-angle X-ray diffraction to measure shape and size of dispersed colloidal particles2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 338, no 1, p. 105-110Article in journal (Refereed)
    Abstract [en]

    Laboratory X-ray diffraction is used to investigate the size and shape of dispersed plate-like and spherical colloidal particles. Analysis of the wide-angle diffraction data provides information about the size and shape of crystals from the width of the Bragg peaks according to the Debye-Scherrer formula. The measurements, data analysis, and evaluation are discussed. It is shown that X-ray diffraction with conventional laboratory equipment on dispersed particles is feasible as a tool to determine both particle size and shape. Data for two samples - gold colloids and nickel (II) hydroxide particles are presented. The advantages and limitations of the method are discussed. X-ray diffraction measurements that are made in combination with dynamic light scattering can be used to estimate the thickness of stabilizing layers of polymers. (C) 2009 Elsevier Inc. All rights reserved.

  • 41.
    Qin, Weiwei
    et al.
    Southwest Jiaotong Univ, Fac Geosci & Environm Engn, Chengdu 611756, Sichuan, Peoples R China..
    Li, Yuan
    Univ Sci & Technol Beijing, Sch Mat Sci & Engn, Beijing 100083, Peoples R China..
    Teng, Yongqiang
    Southwest Jiaotong Univ, Fac Geosci & Environm Engn, Chengdu 611756, Sichuan, Peoples R China.;Chinese Acad Sci, Inst Elect Engn, Beijing 100190, Peoples R China..
    Qin, Tao
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hydrogen bond-assisted synthesis of MoS2/reduced graphene oxide composite with excellent electrochemical performances for lithium and sodium storage2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 512, p. 826-833Article in journal (Refereed)
    Abstract [en]

    MoS2/reduced graphene oxide composites (MoS2/rGO) were successfully prepared by a designed tris (hydroxymethyl)methyl aminomethane (named THAM)-assisted hydrothermal method, which involves the modification of THAM on the surfaces of graphene oxide via hydrogen bonds and then the adsorption of MoO42- on the decorated surfaces due to the electrostatic attraction. The three-dimensional framework of interconnected rGO nanosheets provides good electronic conductivity and facile strain release during the electrochemical reaction, thus enhancing the overall performance of the MoS2-based electrode. Herein, the composite delivers high specific capacity, excellent cycling stability and rate performance for lithium- and sodium-ions batteries (LIBs and SIBs). The MoS2/rGO anode exhibits capacities of 880 mAh g(-1) at 1 A g(-1) after 200 cycles and 396 mAh g(-1) even at 2 A g(-1) after 2000 cycles for LIBs. As to SIBS, the reversible capacities of 485 mAh g(-1) and 339 mAh g(-1) can be retained at 0.1 A g(-1) after 60 cycles and 0.5 A g(-1) after 300 cycles, respectively. Our results demonstrate that the MoS2/rGO anode is one of the attractive anodes for LIBs and SIBS. Furthermore, the facile method can be extended to biosensing, catalytic, and biomedical applications.

  • 42.
    Rodrigues, Leticia
    et al.
    Ludwig Maximilians Univ Munchen, Dept Pharm Pharmaceut Technol & Biopharm, Butenandtstr 5-13, DE-81377 Munich, Germany.
    Schneider, Fabian
    Tech Univ Munich, Walter Schottky Inst, Phys Dept, Coulombwall 4a, DE-85748 Garching, Germany;Tech Univ Munich, Walter Schottky Inst, Inst Adv Study, Coulombwall 4a, DE-85748 Garching, Germany.
    Zhang, Xiaohan
    Tech Univ Munich, Soft Matter Phys Grp, Phys Dept, James Franck Str 1, DE-85748 Garching, Germany.
    Larsson, Elin
    Umea Univ, Dept Integrat Med Biol, Johan Bures Vag 12, SE-90187 Umea, Sweden.
    Moodie, Lindon W. K.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Drug Design and Discovery. Umea Univ, Dept Chem, Linnaeus Vag 1, SE-90736 Umea, Sweden.
    Dietz, Hendrik
    Tech Univ Munich, Walter Schottky Inst, Phys Dept, Coulombwall 4a, DE-85748 Garching, Germany;Tech Univ Munich, Walter Schottky Inst, Inst Adv Study, Coulombwall 4a, DE-85748 Garching, Germany.
    Papadakis, Christine M.
    Tech Univ Munich, Soft Matter Phys Grp, Phys Dept, James Franck Str 1, DE-85748 Garching, Germany.
    Winter, Gerhard
    Ludwig Maximilians Univ Munchen, Dept Pharm Pharmaceut Technol & Biopharm, Butenandtstr 5-13, DE-81377 Munich, Germany.
    Lundmark, Richard
    Umea Univ, Dept Integrat Med Biol, Johan Bures Vag 12, SE-90187 Umea, Sweden.
    Hubert, Madlen
    Umea Univ, Dept Integrat Med Biol, Johan Bures Vag 12, SE-90187 Umea, Sweden.
    Cellular uptake of self-assembled phytantriol-based hexosomes is independent of major endocytic machineries2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 553, p. 820-833Article in journal (Refereed)
    Abstract [en]

    Despite increasing interests in non-lamellar liquid crystalline dispersions, such as hexosomes, for drug delivery, little is known about their interactions with cells and mechanism of cell entry. Here we examine the cellular uptake of hexosomes based on phytantriol and mannide monooleate by HeLa cells using live cell microscopy in comparison to conventional liposomes. To investigate the importance of specific endocytosis pathways upon particle internalization, we silenced regulatory proteins of major endocytosis pathways using short interfering RNA. While endocytosis plays a significant role in liposome internalization, hexosomes are not taken up via endocytosis but through a mechanism that is dependent on cell membrane tension. Biophysical studies using biomembrane models highlighted that hexosomes have a high affinity for membranes and an ability to disrupt lipid layers. Our data suggest that direct biomechanical interactions of hexosomes with membrane lipids play a crucial role and that the unique morphology of hexosomes is vital for their membrane activity. Based on these results, we propose a mechanism, where hexosomes destabilize the bilayer, allowing them to "phase through" the membrane. Understanding parameters that influence the uptake of hexosomes is critical to establish them as carrier systems that can potentially deliver therapeutics efficiently to intracellular sites of action.

  • 43.
    Sandberg, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Mellin, Lisa
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Gelius, Ulrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Caldwell, Karin D.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Surface analysis of pure and complex mucin coatings2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 333, no 1, p. 180-187Article in journal (Refereed)
    Abstract [en]

    In the past, we introduced the idea of using mucin coatings to improve biomaterials performance. Here, we evaluate non-radioactive methods for the analysis of pure and human host protein-containing (complex) mucin coatings on a real-type substrate (Thermanox). A common protein quantification assay (mBCA) was combined with mass-calibrated, enzyme-amplified assays based on lectin (ELLA) and antibody (ELISA)   recognition, to determine the total and specific amounts of surface-associated proteins. Model studies showed the mBCA assay to be of limited use at low mass loads, and steric effects to influence the ELLA at high surface layer densities. Non-specific responses due to   substrate interaction were low for the ELLA and ELISAs. Cross-reactions were observed during ELLA analysis of analytes sharing high degree of O-glycosylation. Combined mBCA-ELLA-ELISA analysis suggested that mucin desorption was low upon protein addition and that low concentrations of ELISA-determined Protein for the complex coatings Could be explained in terms of low accessibility of proteins to the bulk environment. Specifically, a methodology is presented for the determination of the fraction of surface-exposed, presumed bioactive proteins in a complex mucin coating. Finally, X-ray photoelectron spectroscopy and infrared reflectance spectroscopy combined with multivariate data analysis were proven useful in the evaluation of mucin-based coatings.

  • 44. Schmidtchen, Artur
    et al.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    (Lipo)polysaccharide interactions of antimicrobial peptides2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 449, p. 136-142Article in journal (Refereed)
    Abstract [en]

    Due to rapidly increasing resistance development against conventional antibiotics, as well as problems associated with diseases either triggered or deteriorated by infection, antimicrobial and anti-inflammatory peptides have attracted considerable interest during the last few years. While there is an emerging understanding of the direct antimicrobial function of such peptides through bacterial membrane destabilization, the mechanisms of their anti-inflammatory function are less clear. We here summarize some recent results obtained from our own research on anti-inflammatory peptides, with focus on peptide(lipo)polysaccharide interactions. (C) 2014 Elsevier Inc. All rights reserved.

  • 45.
    Sharma, Prabhakar
    et al.
    Aalborg University.
    Flury, Markus
    Washington State University.
    Zhou, Jun
    Washington State University.
    Detachment of colloids from a solid surface by a moving air–water interface2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 326, no 1, p. 143-150Article in journal (Refereed)
    Abstract [en]

    Colloid attachment to liquid–gas interfaces is an important process used in industrial applications toseparate suspended colloids from the fluid phase. Moving gas bubbles can also be used to removecolloidal dust from surfaces. Similarly, moving liquid–gas interfaces lead to colloid mobilization in thenatural subsurface environment, such as in soils and sediments. The objective of this study was toquantify the effect of moving air–water interfaces on the detachment of colloids deposited on an airdriedglass surface, as a function of colloidal properties and interface velocity. We selected four typesof polystyrene colloids (positive and negative surface charge, hydrophilic and hydrophobic). The colloidswere deposited on clean microscope glass slides using a flow-through deposition chamber. Air–waterinterfaces were passed over the colloid-deposited glass slides, and we varied the number of passagesand the interface velocity. The amounts of colloids deposited on the glass slides were visualized usingconfocal laser scanning microscopy and quantified by image analysis. Our results showed that colloidsattached under unfavorable conditions were removed in significantly greater amounts than those attachedunder favorable conditions. Hydrophobic colloids were detached more than hydrophilic colloids. Theeffect of the air–water interface on colloid removal was most pronounced for the first two passagesof the air–water interface. Subsequent passages of air–water interfaces over the colloid-deposited glassslides did not cause significant additional colloid removal. Increasing interface velocity led to decreasedcolloid removal. The force balances, calculated from theory, supported the experimental findings, andhighlight the dominance of detachment forces (surface tension forces) over the attachment forces (DLVOforces).

  • 46.
    Silvander, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Vesicle solubilization by alkyl sulfate surfactants: A cryo-TEM study of the vesicle to micelle transition1996In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 179, no 1, p. 104-113Article in journal (Other academic)
    Abstract [en]

    The solubilization of small unilamellar lecithin vesicles by some different alkyl sulfate surfactants (C10SO4-, C12SO4-, and C14SO4-) was investigated by means of light scattering and cryo-transmission electron microscopy. All surfactants were found to induce vesicle growth at subsolubilizing concentrations and a transformation into small globular lipid/surfactant mixed micelles at high surfactant concentrations. The surfactant chain length, however, was found to have a profound influence both on the amount of surfactant needed for solubilization of the lipid bilayer and on the type of structures formed during the vesicle to micelle transition. For C10SO4- a coexistence between vesicles composed of normal lamellar (L(alpha)) phase and thread-like micelles was observed, whereas during solubilization with C12SO4- and C14SO4- an intermediate, presumably holey lamellar, phase appeared before the bilayers were eventually solubilized into lipid/surfactant mixed micelles. The above observations pertain to measurements made in buffer solutions containing 150 mM NaCl. Upon decreasing the salt concentration, disk-shaped micelles, and at higher surfactant concentration thread-like micelles, frequently connected via three-way junctions, were observed during solubilization with C12SO4-.

  • 47.
    Strömstedt, Adam A.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Wessman, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Ringstad, Lovisa
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Effect of lipid headgroup composition on the interaction between melittin and lipid bilayers2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 311, no 1, p. 59-69Article in journal (Refereed)
    Abstract [en]

    The effect of the lipid polar headgroup on melittin-phospholipid interaction was investigated by cryo-TEM, fluorescence spectroscopy, ellipsometry, CD, electrophoresis and photon correlation spectroscopy. In particular, focus was placed on the effect of the lipid polar headgroup on peptide adsorption to, and penetration into, the lipid bilayer, as well as on resulting colloidal stability effects for large unilamellar liposomes. The effect of phospholipid headgroup properties on melittin-bilayer interaction was addressed by comparing liposomes contg. phosphatidylcholine, -acid, and -inositol at varying ionic strength. Increasing the bilayer neg. charge leads to an increased liposome tolerance toward melittin which is due to an electrostatic arrest of melittin at the membrane interface. Balancing the electrostatic attraction between the melittin pos. charges and the phospholipid neg. charges through a hydration repulsion, caused by inositol, reduced this surface arrest and increased liposome susceptibility to the disruptive actions of melittin. Furthermore, melittin was demonstrated to induce liposome structural destabilization on a colloidal scale which coincided with leakage induction for both anionic and zwitterionic systems. The latter findings thus clearly show that coalescence, aggregation, and fragmentation contribute to melittin-induced liposome leakage, and that detailed mol. analyses of melittin pore formation are incomplete without considering also these colloidal aspects.

  • 48. Suriyanarayanan, Subrarnanian
    et al.
    Lee, Hung-Hsun
    Liedberg, Bo
    Aastrup, Teodor
    Nicholls, Ian A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Protein-resistant hyperbranched polyethyleneimine brush surfaces2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 396, p. 307-315Article in journal (Refereed)
    Abstract [en]

    A novel hyperbranched polyethyleneimine (PEI) modified gold surface has been designed, fabricated, and investigated with respect to its ability to resist non-specific adsorption of proteins. The facile synthesis strategy, based on self-assembly, involves immobilization of polyethyleneimine to gold surfaces modified with 11-mercaptoundecanoic acid (MuDA) monolayers using traditional carbodiimide chemistry. The hyperbranched polymer brushes were characterized by X-ray photoelectron spectroscopy (XPS). Reflection absorption infrared spectroscopy (RAIRS) and ellipsometry measurements showed the thickness of the PEI brushes increases with adsorption solution ionic strength. Polymer brush surface concentrations can be improved from 2560 to 3880 chains/mu m(2) by changing the ionic strength of the adsorption solution (PBS) by varying NaCl concentration from 0 to 650 mM. Protein adsorption (pH 7.4) was evaluated under flow injection analysis (FIA) conditions using a quartz crystal microbalance (QCM). The PEI brushes suppress protein adsorption, for example, cytochrome C, bovine serum albumin (BSA), and ribonuclease A, to less than 0.08 mu g/cm(2) and the protein resistance increases with increasing ionic strength of the carrier solution, performance comparable to that achieved with comparable PEG-coated surfaces. The PEI brushes were exceptionally stable, with adsorption characteristics maintained after 6 months storage in aqueous conditions (pH 7.4, 25 degrees C, PBS). The potential of hyperbranched PEI structures as protein-resistant surfaces is discussed. 

  • 49.
    Wessman, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Morin, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Reijmar, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Effect of α-helical peptides on liposome structure: A comparative study of melittin and alamethicin2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 346, no 1, p. 127-135Article in journal (Refereed)
    Abstract [en]

    Cryo-transmission electron microscopy was used in combination with turbidity and leakage measurements to explore and compare the membrane perturbing effects of melittin and alamethicin on POPC-based liposomes of varying composition. The results show that the two peptides, despite their differences in physico-chemical properties and proposed mode of action, induce similar structural effects on the liposomes. Importantly, whereas low peptide concentrations leave pure POPC liposomes intact and seemingly unperturbed, POPC liposomes supplemented with 40 mol.% cholesterol change their shape, rupture and fuse in response to the addition of both melittin and alamethicin. In the case of alamethicin, but not melittin, fusion is effectively prevented by inclusion of 10 mol.% POPG in the liposome membranes. By means of a competitive binding assay we furthermore show that alamethicin, in line with earlier findings for melittin, possess high affinity for positively curved lipid surfaces. Moreover, results from the present study show that magainin 2 has a similar preference for curved surfaces.

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