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  • 1.
    Ahrén, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Selegård, Linnéa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Klasson, Anna
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Abrikossova, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Skoglund, Caroline
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Bengtsson, Torbjörn
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, The Institute of Technology.
    Engström, Maria
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Synthesis and Characterization of PEGylated Gd2O3 Nanoparticles for MRI Contrast Enhancement2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 8, p. 5753-5762Article in journal (Refereed)
    Abstract [en]

    Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study, we report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in MRI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3−5 nm) gadolinium oxide (DEG-Gd2O3) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd2O3 nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd2O3 nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r1 and r2 values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd2O3. Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is, an extremely high MR signal at the cellular and molecular level.

  • 2.
    Ahualli, S.
    et al.
    Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Granada, Granada, Spain.
    Delgado, A.
    Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Granada, Granada, Spain.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    White, L.R.
    Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA.
    Dynamic electrophoretic mobility of concentrated dispersions of spherical colloidal particles. On the consistent use of the cell model2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 16, p. 7041-7051Article in journal (Refereed)
    Abstract [en]

    This paper outlines a complete and self-consistent cell model theory of the electrokinetics of dense spherical colloidal suspensions for general electrolyte composition, frequency of applied field, ? potential, and particle size. The standard electrokinetic equations, first introduced for any given particle configuration, are made tractable to computation by averaging over particle configurations. The focus of this paper is on the systematic development of suitable boundary conditions at the outer cell boundary obtained from global constraints on the suspension. The approach is discussed in relation to previously published boundary conditions that have often been introduced in an ad hoc manner. Results of a robust numerical calculation of high-frequency colloidal transport properties, such as dynamic mobility, using the present model are presented and compared with some existing dense suspension models. © 2006 American Chemical Society.

  • 3. Attard, P
    et al.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Effective spring constant of bubbles and droplets2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 26, p. 8217-8223Article in journal (Refereed)
    Abstract [en]

    It is shown that gas bubbles and liquid droplets respond as hookean springs to applied loads in the experimental weak force regime. An analytic expression is obtained for the spring constant that is identical for both, linear in the surface tension gamma, and logarithmically dependent on the lengths (the decay length of the interaction, the radius of the bubble or droplet, and the radius of the particle or probe). For acute interior contact angles greater than about 20 degrees, it is typically in the range 0.8-1.2 gamma, in agreement with published atomic force microscopy data, and it increases logarithmically for smaller contact angles. Analytic expressions are also obtained for the deformed profile, the extent of the dimple and of the interaction region, the wrapping radius, and the rupture force.

  • 4.
    Basabe-Desmonts, L
    et al.
    Dublin City University.
    Ramstrom, Sofia
    Royal College of Surgeons in Ireland, Dublin.
    Meade, G
    Royal College of Surgeons in Ireland (RCSI), Dublin.
    O'Neill, S
    Royal College of Surgeons in Ireland (RCSI), Dublin.
    Riaz, A
    Dublin City University.
    Lee, L P
    Dublin City University.
    Ricco, A J
    Dublin City University.
    Kenny, D
    Royal College of Surgeons in Ireland (RCSI), Dublin.
    Single-step separation of platelets from whole blood coupled with digital quantification by interfacial platelet cytometry (iPC)2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 18, p. 14700-14706Article in journal (Refereed)
    Abstract [en]

    We report the efficient single-step separation of individual platelets from unprocessed whole blood, enabling digital quantification of platelet function using interfacial platelet cytometry (iPC) on a chip. iPC is accomplished by the precision micropatterning of platelet-specific protein surfaces on solid substrates. By separating platelets from whole blood using specific binding to protein spots of a defined size, iPC implements a simple incubate-and-rinse approach, without sample preparation, that enables (1) the study of platelets in the physiological situation of interaction with a protein surface, (2) the choice of the number of platelets bound on each protein spot, from one to many, (3) control of the platelet-platelet distance, including the possibility to study noninteracting single platelets, (4) digital quantification (counting) of platelet adhesion to selected protein matrices, enabling statistical characterization of platelet subpopulations from meaningfully large numbers of single platelets, (5) the study of platelet receptor expression and spatial distribution, and (6) a detailed study of the morphology of isolated single platelets at activation levels that can be manipulated. To date, we have demonstrated 1-4 of the above list. Platelets were separated from whole blood using iPC with fibrinogen, von Willebrand factor (VWF), and anti-CD42b antibody printed "spots" ranging from a fraction of one to several platelet diameters (2-24 μm). The number of platelets captured per spot depends strongly on the protein matrix and the surface area of the spot, together with the platelet volume, morphology, and activation state. Blood samples from healthy donors, a May-Hegglin-anomaly patient, and a Glanzmann's Thrombasthenia patient were analyzed via iPC to confirm the specificity of the interaction between protein matrices and platelets. For example, the results indicate that platelets interact with fibrinogen spots only through the fibrinogen receptor (αIIbβ3) and, relevant to diagnostic applications, platelet adhesion correlates strongly with normal versus abnormal platelet function. A critical function of platelets is to adhere to regions of damage on blood vessel walls; in contrast to conventional flow cytometry, where platelets are suspended in solution, iPC enables physiologically relevant platelet bioassays based on platelet/protein-matrix interactions on surfaces. This technology should be inexpensive to implement in clinical assay format, is readily integrable into fluidic microdevices, and paves the way for high-throughput platelet assays from microliter volumes of whole blood.

  • 5.
    Beyer, Sebastian
    et al.
    Gelsenkirchen University of Applied Sciences, Germany.
    Mak, Wing Cheung
    National University of Singapore.
    Trau, Dieter
    National University of Singapore.
    Reverse-phase LbL-encapsulation of highly water soluble materials by layer-by-layer polyelectrolyte self-assembly2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 17, p. 8827-8832Article in journal (Refereed)
    Abstract [en]

    We report on a novel method for the encapsulation of highly water soluble materials by using layer-by-layer (LbL) polyelectrolyte self-assembly. State of the art polyelectrolyte self-assembly LbL coating and encapsulation methods are only applicable to insoluble or poorly water soluble template materials, because the process is performed in water causing dissolution of the solid template. Our method extends the material spectrum to highly water soluble template materials by using non-ionized polyelectrolytes in an organic phase (reverse-phase) instead of polyelectrolyte salts in an aqueous environment. By using the reverse-phase layer-by-layer (RP-LbL) technique, we have demonstrated the direct encapsulation of proteins, glucose, vitamin C, and inorganic salts in the solid state. Multilayer deposition was proven, layer thickness was determined by AFM, and the advantage of the method to prepare powders of encapsulated materials was demonstrated. The method is simple, robust, and applicable to a broad range of substances with potential applications in several industries.

  • 6.
    Björk, Emma M.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Tuning the shape of mesoporous silica particles by alterations in parameter space: from rods to platelets2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 44, p. 13551-13561Article in journal (Refereed)
    Abstract [en]

    The knowledge of how to control the pore size and morphology of separated mesoporous silica particles is crucial for optimizing their performance in applications, such as molecular sieves and drug delivery systems. In this work, we have systematically studied the effects of various synthesis parameters to gain a deeper understanding of how particle morphologies can be altered. It was found that the morphology for isolated particles of SBA-15 type, with unusually short and wide pores, could be altered from rods to platelets by variations in the NH4F concentration. The pore length is nearly constant (similar to 300 nm) for the different morphologies, but the particle width is increasing from 200 nm to >3 mu m when decreasing the amount of NH4F, and the pore size can be tuned between 10 and 13 nm. Furthermore, other synthesis parameters such as heptane concentration, pH, silica precursor, and additions of ions have also been studied. The trend regarding particle width is independent of heptane concentration, at the same time as heptane increases the particle length up to a plateau value of similar to 500 nm. In all, parameters controlling particle width, length, and pore size have been separated in order to evaluate their function in the particle formation. Additionally, it was found that the formation time of the particles is strongly affected by the fluoride ion concentration, and a mechanism for particle formation for this system, where micelles transform from a foam, to multilamellar vesicles, and finally to cylindrical micelles, is suggested.

  • 7. Blomberg, Eva
    et al.
    Claesson, Per M.
    Konradsson, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Globotriose- and oligo(ethylene glycol)-terminated self-assembled monolayers: Surface forces, wetting, and surfactant adsorption2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 24, p. 10038-10046Article in journal (Refereed)
    Abstract [en]

    A set of oligo( ethylene glycol)-terminated and globotriose-terminated self-assembled monolayers (SAMs) has been prepared on gold substrates. Such model surfaces are well defined and have good stability due to the strong binding of thiols and disulfides to the gold substrate. They are thus very suitable for addressing questions related to effects of surface composition on wetting properties, surface interactions, and surfactant adsorption. These issues are addressed in this report. Accurate wetting tension measurements have been performed as a function of temperature using the Wilhelmy plate technique. The results show that the nonpolar character of oligo( ethylene glycol)-terminated SAMs increases slightly but significantly with temperature in the range 20-55 degrees C. On the other hand, globotriose-terminated SAMs are fully wetted by water at room temperature. Surface forces measurements have been performed and demonstrated that the interactions between oligo( ethylene glycol)-terminated SAMs are purely repulsive and similar to those determined between adsorbed surfactant layers with the same terminal headgroup. On the other hand, the interactions between globotriose-terminated SAMs include a short-range attractive force component that is strongly affected by the packing density in the layer. In some cases it is found that the attractive force component increases with contact time. Both these observations are rationalized by an orientation- and conformation-dependent interaction between globotriose headgroups, and it is suggested that hydrogen-bond formation, directly or via bridging water molecules, is the molecular origin of these effects.

  • 8.
    Boström, Mathias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Kunz, W.
    Inst. of Phys. and Theor. Chemistry, University of Regensburg, D-93040 Regensburg, Germany.
    Ninham, B.W.
    Inst. of Phys. and Theor. Chemistry, University of Regensburg, D-93040 Regensburg, Germany, Res. Sch. of Phys. Sci. and Eng., Australian National University, Canberra 0200, Australia.
    Hofmeister effects in surface tension of aqueous electrolyte solution2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 6, p. 2619-2623Article in journal (Refereed)
    Abstract [en]

    The surface tension of electrolyte solutions shows marked specific ion effects. We here show an important role for both ionic solvation energies and ionic dispersion potentials in determining this ion specific surface tension of salt solutions. The ion self-free energy changes when an ion moves from bulk solution into the interfacial region, with its decreasing water density profile. We will show that the solvation energies of different ions correlate very well with the surface tension of salt solutions. Inclusion of this distance-dependent self-free energy contribution brings qualitative agreement with experiments and the right Hofmeister series. This is so not only for surface tension changes but also for measured surface potentials. The inclusion of ionic dispersion interaction potentials further improves the agreement with experiments. We discuss how further progress in the theory of the surface tension of salts can be achieved. © 2005 American Chemical Society.

  • 9.
    Boström, Mathias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Kunz, W.
    Institute of Physical and Theoretical Chemistry University of Regensburg.
    Ninham, B.W.
    Research School of Physical Sciences and Engineering Australian National University.
    Hofmeister Effects in Surface Tension of Aqueous Electrolyte Solution2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, p. 2619-2623Article in journal (Refereed)
  • 10.
    Boström, Mathias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Ninham, B.W.
    Res. Sch. of Phys. Sci. and Eng., Australian National University, Canberra, 0200, Australia, Inst. of Phys. and Theor. Chemistry, University of Regensburg, D-93040 Regensburg, Germany.
    Dispersion self-free energies and interaction free energies of finite-sized ions in salt solutions2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 18, p. 7569-7574Article in journal (Refereed)
    Abstract [en]

    The role for many-body dipolar (dispersion) potentials in ion-solvent and ion-solvent-interface interactions is explored. Such many-body potentials, accessible in principle from measured dielectric data, are necessary in accounting for Hofmeister specific ion effects. Dispersion self-energy is the quantum electrodynamic analogue of the Born electrostatic self-energy of an ion. We here describe calculations of dispersion self-free energies of four different anions (OH-, Cl-, Br-, and I-) that take finite ion size into account. Three different examples of self-free energy calculations are presented. These are the self-free energy of transfer of an ion to bulk solution, which influences solubility, the dispersion potential acting between one ion and an air-water interface (important for surface tension calculations), and the dispersion potential acting between two ions (relevant to activity coefficient calculations). To illustrate the importance of dispersion self-free energies, we compare the Born and dispersion contributions to the free energy of ion transfer from water to air (oil). We have also calculated the change in interfacial tension with added salt for air (oil)-water interfaces. A new model is used that includes dispersion potentials acting on the ions near the interface, image potentials, and ions of finite size that are allowed to spill over the solution-air interface. It is shown that interfacial free energies require a knowledge of solvent profiles at the interface.

  • 11.
    Bradshaw-Hajek, B. H.
    et al.
    Univ S Australia, Sch Math and Stat, Mawson Lakes, SA 5082, Australia.
    Miklavcic, Stanley J
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    White, L. R.
    Univ S Australia, Sch Math and Stat, Mawson Lakes, SA 5082, Australia.
    Dynamic Dielectric Response of Concentrated Colloidal Dispersions: Comparison between Theory and Experiment2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 4, p. 1961-1969Article in journal (Refereed)
    Abstract [en]

    The cell-model electrokinetic theory of Ahualli et al. Langmuir 2006, 22, 704 1; Ahualli et al. J. Colloid Interface Sci. 2007, 309, 342; and Bradshaw-Hajek et al. Langmuir 2008, 24, 4512 is applied to a dense suspension of charged spherical particles, to exhibit the systems dielectric response to an applied electric field as a function of solids volume fraction. The models predictions of effective permittivity and complex conductivity are favorably compared with published theoretical calculations and experimental measurements on dense colloidal systems. Physical factors governing the volume fraction dependence of the dielectric response are discussed.

  • 12. Bradshaw-Hajek, B.H.
    et al.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Whitet, L.R.
    Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, University of South Australia, Mawson Lakes, SA 5095, Australia.
    Frequency-dependent electrical conductivity of concentrated dispersions of spherical colloidal particles2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 9, p. 4512-4522Article in journal (Refereed)
    Abstract [en]

    This paper outlines the application of a self-consistent cell-model theory of electrokinetics to the problem of determining the electrical conductivity of a dense suspension of spherical colloidal particles. Numerical solutions of the standard electrokinetic equations, subject to self-consistent boundary conditions, are implemented in formulas for the electrical conductivity appropriate to the particle-averaged cell model of the suspension. Results of calculations as a function of frequency, zeta potential, volume fraction, and electrolyte composition, are presented and discussed. © 2008 American Chemical Society.

  • 13.
    Carrick, Christopher
    et al.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Lindström, Stefan
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    Larsson, Per Tomas
    KTH Royal Institute of Technology, Stockholm, Swede; Innventia AB, Stockholm Sweden .
    Wågberg, Lars
    KTH Royal Institute of Technology, Stockholm, Sweden .
    Lightweight, highly compressible, noncrystalline cellulose capsules2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 26, p. 7635-7644Article in journal (Refereed)
    Abstract [en]

    We demonstrate how to prepare extraordinarily deformable, gas-filled, spherical capsules from nonmodified cellulose. These capsules have a low nominal density, ranging from 7.6 to 14.2 kg/m(3), and can be deformed elastically to 70% deformation at 50% relative humidity. No compressive strain-at-break could be detected for these dry cellulose capsules, since they did not rupture even when compressed into a disk with pockets of highly compressed air. A quantitative constitutive model for the large deformation compression of these capsules is derived, including their high-frequency mechanical response and their low-frequency force relaxation, where the latter is governed by the gas barrier properties of the dry capsule. Mechanical testing corroborated these models with good accuracy. Force relaxation measurements at a constant compression rendered an estimate for the gas permeability of air through the capsule wall, calculated to 0.4 mL mu m/m(2) days kPa at 50% relative humidity. These properties taken together open up a large application area for the capsules, and they could most likely be used for applications in compressible, lightweight materials and also constitute excellent model materials for adsorption and adhesion studies.

  • 14.
    Cortat, Frédéric
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Using stable and unstable profiles to deduce deformation limits of the air-water interface2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 8, p. 3208-3220Article in journal (Refereed)
    Abstract [en]

    The shape of the air-water interface deformed by a van der Waals stress induced by a paraboloid shaped solid body is addressed and discussed. Emphasis is placed on the existence limit of solutions to the governing Euler-Lagrange equation for the equilibrium shape. Two legitimate solutions, one stable and one unstable, are found to converge at the existence limit, giving a numerical criterion for establishing critical physical conditions guaranteeing absolute stability. Insight is aided by a study of an analogous mechanical problem that exhibits very similar properties. Among numerical data produced are critical lower height limits of the paraboloid to the air-water surface and associated peak deformation heights and their dependencies on physical parameters. Of further interest to experimentalists in the surface force field are the variations in peak deformation height and total surface force on the solid as a function of position of the paraboloid, paraboloid geometry, and strength of the van der Waals stress.

  • 15. De Cupere, V.
    et al.
    Tant, J.
    Viville, P.
    Lazzaroni, R.
    Osikowicz, Wojciech
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Geerts, Y. H.
    Effect of interfaces on the alignment of a discotic liquid-crystalline phthalocyanine2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 18, p. 7798-7806Article in journal (Refereed)
    Abstract [en]

    This paper deals with the influence of the nature and number of solid interfaces on the alignment of the columns in a semiconducting discotic liquid crystal. The solid substrates have been characterized in terms of their roughness and surface energy. The alignment of the discotic liquid crystal columns on these substrates has been determined by optical microscopy under crossed polarizers and by tapping-mode atomic force microscopy. The nature of the substrates has negligible influence on the alignment. The key parameter is the confinement imposed to the film. These surprising observations are explained by the antagonist alignment role of gas and solid interfaces. © 2006 American Chemical Society.

  • 16.
    Duineveld, P.C.
    et al.
    Philips Research, Prof. Holstlaan 4, 5656 AA Eindhoven, Netherlands.
    Lilja, M.
    Johansson, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Diffusion of solvent in PDMS elastomer for micromolding in capillaries2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 24, p. 9554-9559Article in journal (Refereed)
    Abstract [en]

    Micromolding in capillaries is a soft lithography method for patterning materials. We have studied the diffusion of solvent from the excavated microsized channels in the stamp into the PDMS material, both theoretically and experimentally. It was demonstrated that a model of 1-D diffusion of solvent through a PDMS stamp, coupled with a mass conservation of the solvent in the channels, leads to a quantitatively accurate model for the velocity of the boundary between liquid-filled and vapor-filled microchannels in the stamp. With the model the diffusion coefficient of the solvent into PDMS was successfully determined.

  • 17. Dunér, G
    et al.
    Andersson, H
    Myrskog, Annica
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Hedlund, M
    Aastrup, T
    Ramstrom, o
    Surface-confined photopolymerization of pH-responsive acrylamide/acrylate brushes on polymer thin films2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 14, p. 7559-7564Article in journal (Refereed)
    Abstract [en]

    Dynamic acrylamide/acrylate polymeric brushes were synthesized at gold-plated quartz crystal surfaces. The crystals were initially coated with polystyrene-type thin films, derivatized with photolabile iniferter groups, and subsequently subjected to photoinitiated polymerization in acrylamide/acrylate monomer feeds. This surface-confined polymerization method enabled direct photocontrol over the polymerization, as followed by increased frequency responses of the crystal oscillations in a quartz crystal microbalance (QCM). The produced polymer layers were also found to be highly sensitive to external acid/base stimuli. Large oscillation frequency shifts were detected when the brushes were exposed to buffer solutions of different pH. The dynamic behavior of the resulting polymeric brushes was evaluated, and the extent of expansion and contraction of the films was monitored by the QCM setup in situ in real time. The resulting responses were rapid, and the effects were fully reversible. Low pH resulted in full contractions of the films, whereas higher pH yielded maximal expansion in order to minimize repulsion around the charged acrylate centers. The surfaces also proved to be very robust because the responsiveness was reproducible over many cycles of repeated expansion and contraction. Using ellipsometry, copolymer layers were estimated to be ∼220 nm in a collapsed state and ∼340 nm in the expanded state, effectively increasing the thickness of the film by 55%. © 2008 American Chemical Society.

  • 18.
    Ederth, T.
    et al.
    Department of Chemistry, Surface Chemistry, Royal Institute of Technology, SE-100 44 Stokholm, Sweden, Institute for Surface Chemistry, Box 5607, SE-114 86 Stockholm, Sweden, Phys. and Theor. Chem. Laboratory, South Parks Road, Oxford OX1 3Q2, United Kingdom.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Influence of wetting properties on the long-range `hydrophobic' interaction between self-assembled alkylthiolate monolayers2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, no 5, p. 2177-2184Article in journal (Refereed)
    Abstract [en]

    The effect of solid-liquid interfacial energy on the long-range attraction between self-assembled thiolate monolayers in water has been studied by direct force measurements. The solid-liquid interfacial energy was tuned by changing the properties of the solid surface: the thiolate monolayers were prepared by self-assembly of mixtures of methyl- and hydroxyl-functionalized alkylthiols onto thin gold films. The wetting properties were examined by contact angle measurements with the Wilhelmy plate method. Our results show that the shape of the long-ranged attractive force is sensitive to the advancing solid-liquid contact angle: whenever it exceeds 90° the force profiles are discontinuous and contains steps, whereas no attraction beyond the van der Waals force is observed for contact angles lower than 90°. We attribute the steps in the long-range attraction between hydrophobic surfaces to bridging of microscopic bubbles residing on the surfaces, and we conclude that the stability of these bubbles are related to macroscopic contact angles.

  • 19.
    Ederth, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. MariboHilleshog Res AB, Sweden.
    Swelling of Thin Poly(ethylene glycol)-Containing Hydrogel Films it Water Vapor-A Neutron Reflectivity Study2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 19, p. 5517-5526Article in journal (Refereed)
    Abstract [en]

    Hydrogels are widely used in biomedicine and for bioanalytical purposes, normally under wet conditions. For certain applications, processing steps, or process monitoring, hydrogel films are used or treated under ambient conditions, and because they are hygroscopic, it is of interest to investigate how they respond to changes in atmospheric humidity. We have used neutron reflectometry to follow the swelling of thin UV-polymerized hydrogel films in air under different relative humidities (RHs). These polymers were prepared to similar thicknesses on silica and gold substrates, and the chemical similarity between them was verified by infrared spectroscopy. The swelling in response to variations in RH was different for the layers on the two substrate types, reflecting structural changes induced by differences in the UV exposure required to achieve a given polymer thickness, as demonstrated also by differences in the Flory-Huggins interaction parameter, obtained by fitting a Flory-Huggins-type sorption model to the swelling data. Wetting studies show small changes in contact angles with surrounding humidity variations, indicating that structural reorganization at the interface in response to humidity changes is limited.

    The full text will be freely available from 2019-04-19 12:32
  • 20.
    Ederth, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Pettitt, M E
    University of Birmingham.
    Nygren, Patrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Zhou, Ye
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Falk, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Callow, M E
    University of Birmingham.
    Callow, J A
    University of Birmingham.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Interactions of Zoospores of Ulva linza with Arginine-Rich Oligopeptide Monolayers2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 16, p. 9375-9383Article in journal (Refereed)
    Abstract [en]

    We recently reported oil the strong interactions of zoospores of the green alga, Ulva linza with all arginine-rich oligopeptide self-assembled monolayer (SAM) [Biofouling 2008, 24, 303-312], where the arginine-rich peptide induced not only high spore settlement, but also a form of abnormal settlement, or "pseudo-settlement", whereby it proportion of spores do not go through the normal process of surface exploration, adhesive exocytosis, and loss of flagella. Further. it was demonstrated that both the total number of settled spores and the fraction of pseudosettled spores were related to the surface density of the arginine-rich peptide. Here we present a further investigation of the interactions of zoospores of ulva with a set of oligomeric, de nom designed, arginine-rich peptides, specifically aimed to test the effect of peptide primary structure on the interaction. Via variations in the peptide length and by permutations in the amino acid sequences, we gain further insight into the spore-surface interactions. The interpretation of the biological assays is supported by physicochemical characterization of the SAMs using infrared spectroscopy, ellipsometry, and contact angle measurement. Results confirm the importance of arginine residues for the anomalous pseudosettlement, and we found that settlement is modulated by variations in both the total length and peptide primary structure. To elucidate the Causes of the anomalous settlement and the possible relation to peptide-membrane interactions, we also compared the settlement of the "naked" zoospores of Ulva(which present it lipoprotein membrane to the exterior without a discrete polysaccharide cell wall), with the settlement of diatoms (unicellular algae that are surrounded by it silica cell wall), onto the peptide SAMs. Cationic SAMs do not notably affect settlement (attachment), adhesion strength, or viability of diatom cells, Suggesting that the effect of the peptides on zoospores of Ulva is mediated via specific peptide-membrane interactions.

  • 21.
    Ederth, Thomas
    et al.
    Phys and Theoret Chem Lab, Oxford OX1 3QZ, England.
    Thomas, R K
    Phys and Theoret Chem Lab, Oxford OX1 3QZ, England; .
    A neutron reflectivity study of drainage and stratification of AOT foam films2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, no 19, p. 7727-7733Article in journal (Refereed)
    Abstract [en]

    Structural properties of Aerosol-OT (AOT) foam films were studied by neutron reflectometry. The drainage of large (10 cm(2)), horizontally oriented AOT films under zero applied external pressure is slow and proceeds from thick colored or gray films to black films of approximately 200 Angstrom thickness over many hours, resulting in quasi-static conditions over the time scales required for the acquisition of reflectivity profiles throughout the whole drainage process. After formation of the foam film-while still showing colored interference fringes-and during the early stages of thinning, the appearance of Bragg diffraction peaks demonstrates that the film contains multilamellar structure, in agreement with studies at free air/water interfaces. Upon further reduction of the film thickness, below approximately 250 Angstrom, the reflectivity profile is well fitted by a three-layer slab model with two surfactant layers and an aqueous core with a high surfactant content. The composition of the aqueous core and the manner in which the reflectivity during the latter stages of draining evolves from Bragg peaks to a Kiessig fringe structure indicate stratification within the thin foam film.

  • 22.
    Ekblad, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Tai, Feng-i
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Liedberg , Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Lateral Control of Protein Adsorption on Charged Polymer Gradients2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 6, p. 3755-3762Article in journal (Refereed)
    Abstract [en]

    This work describes the fabrication, characterization, and protein adsorption behavior of charged polymer gradients. The thin gradient films were fabricated by a two-step technique using UV-initiated free-radical polymerization in a reactor with a moving shutter. A homogeneous layer of cationic poly(2-aminoethyl methacrylate hydrochloride) was first formed, followed by a layer of oppositely charged poly(2-carboxyethyl acrylate) with a continuously increasing thickness. Adsorption from protein solutions as well as human blood plasma was investigated by imaging surface plasmon resonance and infrared microscopy. The results showed excessive protein adsorption in the areas where one of the polymers dominated the composition, while there was a clear minimum at an intermediate position of the gradient. The charge of the surface was estimated by direct force measurements and found to correlate well with the protein adsorption, showing the lowest net charge in the same area as the protein adsorption minimum. We therefore hypothesize that a combination of the charged polymers, in the right proportions, can result in a protein-resistant surface due to balanced charges.

  • 23.
    Ekeroth, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Konradsson, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry .
    Hook, F.
    Höök, F., Department of Applied Physics, Chalmers University of Technology, Göteborg University, SE-412 96 Göteborg, Sweden.
    Bivalent-ion-mediated vesicle adsorption and controlled supported phospholipid bilayer formation on molecular phosphate and sulfate layers on gold2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 21, p. 7923-7929Article in journal (Refereed)
    Abstract [en]

    Strategies to form supported lipid assemblies on organophosphate- and organosulfate-monolayer-modified gold surfaces are described. By varying surface treatment and the Mg2+ (Ca2+) content in a solution containing phosphatidylcholine vesicles, we demonstrate (i) efficient formation of supported phosphatidylcholine bilayers (SPBs), (ii) formation of supported nonruptured phosphatidylcholine vesicles, and (iii) reduced phosphatidylcholine vesicle adsorption. Thus, by simply varying the solution conditions, the system can be tuned to controlled formation of either a SPB, supported nonruptured vesicles, or a surface with fairly low coverage of nonruptured vesicles. The profound effects induced on the system by Mg2+ and Ca2+ are assigned to a combination of ion-coordination to the surface, ion-association to the lipid headgroups, and osmotic pressure.

  • 24.
    Enander, Karin
    et al.
    Division of Organic Chemistry, Uppsala University.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Baltzer, Lars
    Division of Organic Chemistry, Department of Chemistry, BMC, Uppsala University, Uppsala, Sweden.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Alpha-helix-inducing dimerization of synthetic polypeptide scaffolds on gold2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 6, p. 2480-2487Article in journal (Refereed)
    Abstract [en]

    Designed, synthetic polypeptides that assemble into four-helix bundles upon dimerization in solution were studied with respect to folding on planar gold surfaces. A model system with controllable dimerization properties was employed, consisting of negatively and positively charged peptides. Circular dichroism spectroscopy and surface plasmon resonance based measurements showed that at neutral pH, the peptides were able to form heterodimers in solution, but unfavorable electrostatic interactions prevented the formation of homodimers. The dimerization propensity was found to be both pH- and buffer-dependent. A series of infrared absorption−reflection spectroscopy experiments of the polypeptides attached to planar gold surfaces revealed that if the negatively charged peptide was immobilized from a loading solution where it was folded, its structure was retained on the surface provided it had a cysteine residue available for anchoring to gold. If it was immobilized as random coil, it remained unstructured on the surface but was able to fold through heterodimerization if subsequently exposed to a positively charged polypeptide. When the positively charged peptide was immobilized as random coil, heterodimerization could not be induced, probably because of high-affinity interactions between the charged primary amine groups and the gold surface. These observations are intended to pave the way for future engineering of functional surfaces based on polypeptide scaffolds where folding is known to be crucial for function.

  • 25.
    Engquist, Isak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lestelius, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Microscopic wettability of ester- and acetate-terminated self-assembled monolayers1997In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 13, no 15, p. 4003-4012Article in journal (Refereed)
    Abstract [en]

    Four different carbonyl-containing self-assembled monolayers (SAMs) of alkanethiolates on gold were studied to assess the impact of the functional group Linked to the carbonyl upon its hydrogen bond accepting capability. These SAMs (HS(CH2)(16)O(C=O)-X,X = CH3, CF3, or C6H5, and HS(CH2)(15)(C=O)OCH3) were thoroughly characterized with contact angle measurements, single wavelength ellipsometry, and infrared reflection-absorption spectroscopy (IRAS) prior to the studies of interaction with D2O. The first three monolayer compounds were introduced by reacting hydroxyl-terminated SAMs (HS(CH2)(16)OH) with either acetyl chloride, trifluoroacetic anhydride, or benzoyl chloride. The behavior of D2O ice on the SAMs was investigated at 100 K with IRAS and temperature programmed desorption (TPD). On all monolayers the D2O molecules were shown to interact with the carbonyl oxygen. The degree of interaction depended upon the termination of the thiol, where the size, structure, and electronegativity of the terminating groups in the molecules comprising the monolayer were found to be important factors. Indications of interaction with the C-O-C oxygen were seen for all compounds, as well as weak interaction between water molecules and the CF3 group of one of the investigated SAMs. Common behavior for all four monolayers with an adsorbed D2O overlayer was a decrease in the number of hydrogen bonds to the substrate when the overlayer was annealed from amorphous ice at 100 K to polycrystalline-like ice at 140 K. The spectral changes accompanying the structural transition were consistent with a change from a mainly flat overlayer to condensed three-dimensional clusters. The bulk-to-surface molecular ratio of adsorbed ice clusters could be assessed by IRAS and correlated to macroscopic wetting properties. Our results infer that microscopic ice clusters on these SAMs qualitatively mimic the shape of macroscopic water drops on the same SAMs. Results of TPD measurements are also consistent with this view.

  • 26.
    Ericsson, Emma
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Bui, Lan
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Site-Specific and Covalent Attachment of His-Tagged Proteins by Chelation Assisted Photoimmobilization: A Strategy for Microarraying of Protein Ligands2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 37, p. 11687-11694Article in journal (Refereed)
    Abstract [en]

    A novel strategy for site-specific and covalent attachment of proteins has been developed, intended for robust and controllable immobilization of histidine (His)-tagged ligands in protein microarrays. The method is termed chelation assisted photoimmobilization (CAP) and was demonstrated using human IgG-Fc modified with C-terminal hexahistidines (His-IgGFc) as the ligand and protein A as the analyte. Alkanethiols terminated with either nitrilotriacetic acid (NTA), benzophenone (BP); or oligo(ethylene glycol) were synthesized and mixed self-assembled monolayers (SAMs) were prepared on gold and thoroughly characterized by infrared reflection absorption spectroscopy (IRAS), ellipsometry, and contact angle goniometry. In the process of CAP, NTA chelates Ni2+ and the complex coordinates the His-tagged ligand in an oriented assembly. The ligand is then photoimmobilized via BP, which forms covalent bonds upon UV light activation. In the development of affinity biosensors and protein microarrays, site-specific attachment of ligands in a fashion where analyte binding sites are available is often preferred to random coupling. Analyte binding performance of ligands immobilized either by CAP or by standard amine coupling was characterized by surface plasmon resonance in combination with IRAS. The relative analyte response with randomly coupled ligand was 2.5 times higher than when site-specific attachment was used. This is a reminder that also when immobilizing ligands via residues far from the binding site, there are many other factors influencing availability and activity. Still, CAP provides a valuable expansion of protein immobilization techniques since it offers attractive microarraying possibilities amenable to applications within proteomics.

  • 27.
    Fyrner, Timmy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lee, Hung-Hsun
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Mangone, Alberto
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Pettitt, Michala E
    University of Birmingham, UK.
    Callow, Maureen E
    University of Birmingham, UK.
    Callow, James A
    University of Birmingham, UK.
    Conlan, Sheelagh L
    Newcastle University, UK.
    Mutton, Robert
    Newcastle University, UK.
    Clare, Anthony S
    Newcastle Universitym, UK.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Saccharide-Functionalized Alkanethiols for Fouling-Resistant Self-Assembled Monolayers: Synthesis, Monolayer Properties, and Antifouling Behavior2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 24, p. 15034-15047Article in journal (Refereed)
    Abstract [en]

    We describe the synthesis of a series of mono-, di-, and trisaccharide-functionalized alkanethiols as well as the formation of fouling-resistant self-assembled monolayers (SAMs) from these. The SAls,,Is were characterized using ellipsometry, wetting measurements, and infrared reflection absorption spectroscopy (WAS). We show that the structure of the carbohydrate moiety affects the packing density and that this also alters the alkane chain organization. Upon increasing the size of the sugar moieties (from mono- to di- and trisaccharides), the structural qualities of the monolayers deteriorated with increasing disorder, and for the trisaccharide, slow reorganization dynamics in response to changes in the environmental polarity were observed. The antifouling properties of these SAMs were investigated through protein adsorption experiments from buffer solutions as well as settlement (attachment) tests using two common marine fouling species, zoospores of the green macroalga Ulva linza and cypris larvae of the barnacle Balanus amphitrite. The SAMs showed overall good resistance to fouling by both the proteins and the tested marine organisms. To improve the packing density of the SAMs with bulky headgroups, we employed mixed SAMs where the saccharide-thiols are diluted with a filler molecule having a small 2-hydroxyethyl headgroup. This method also provides a means by which the steric availability of sugar moieties can be varied, which is of interest for specific interaction studies with surface-bound sugars. The results of the surface dilution study and the low nonspecific adsorption onto the SAMs both indicate the feasibility of this approach.

  • 28.
    Hatamie, Amir
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Shahid Chamran University, Iran.
    Khan, Azam
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. NED University of Engn and Technology, Pakistan.
    Golabi, Mohsen
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Mak, Wing Cheung
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Sadollah Khani, Azar
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. Shahid Chamran University, Iran.
    Alnoor, Hatim
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Zargar, Behrooz
    Shahid Chamran University, Iran.
    Bano, Sumaira
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Nour, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zinc Oxide Nanostructure-Modified Textile and Its Application to Biosensing, Photocatalysis, and as Antibacterial Material2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 39, p. 10913-10921Article in journal (Refereed)
    Abstract [en]

    Recently, one-dimensional nanostructures with different morphologies (such as nanowires, nanorods (NRs), and nanotubes) have become the focus of intensive research, because of their unique properties with potential applications. Among them, zinc oxide (ZnO) nanomaterials has been found to be highly attractive, because of the remarkable potential for applications in many different areas such as solar cells, sensors, piezoelectric devices, photodiode devices, sun screens, antireflection coatings, and photocatalysis. Here, we present an innovative approach to create a new modified textile by direct in situ growth of vertically aligned one-dimensional (1D) ZnO NRs onto textile surfaces, which can serve with potential for biosensing, photocatalysis, and antibacterial applications. ZnO NRs were grown by using a simple aqueous chemical growth method. Results from analyses such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that the ZnO NRs were dispersed over the entire surface of the textile. We have demonstrated the following applications of these multifunctional textiles: (1) as a flexible working electrode for the detection of aldicarb (ALD) pesticide, (2) as a photo catalyst for the degradation of organic molecules (i.e., Methylene Blue and Congo Red), and (3) as antibacterial agents against Escherichia coli. The ZnO-based textile exhibited excellent photocatalytic and antibacterial activities, and it showed a promising sensing response. The combination of sensing, photo catalysis, and antibacterial properties provided by the ZnO NRs brings us closer to the concept of smart textiles for wearable sensing without a deodorant and antibacterial control. Perhaps the best known of the products that is available in markets for such purposes are textiles with silver nanoparticles. Our modified textile is thus providing acceptable antibacterial properties, compared to available commercial modified textiles.

  • 29.
    Hederos, Markus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Synthesis and self-assembly of galactose-terminated alkanethiols and their ability to resist proteins2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 7, p. 2971-2980Article in journal (Refereed)
    Abstract [en]

    The synthesis of two galactose-terminated alkanethiols with the structural formula X−OC2H5NHCO(CH2)15SH (X = 2,3,4,6-tetra-O-methyl-β-d-Gal or β-d-Gal) is described. Single-component and mixed self-assembled monolayers (SAMs) of the methylated and nonmethylated compounds were prepared on gold and subsequently characterized with ellipsometry, contact angle goniometry, and infraredreflection−absorption spectroscopy. Studies of the irreversible protein adsorption onto the SAMs using ex-situ ellipsometry revealed very low levels of fibrinogen and lysozyme adsorption onto mixed SAMs displaying advancing water contact angles between 24° and 45° and below 45°, respectively. A monomethylated compound (X = 6-O-methyl-β-d-Gal) was also synthesized and assembled on gold. This particular compound was found to possess wettability properties corresponding to the low adsorption regime of the mixed SAMs, and the results from the same set of fibrinogen and lysozyme adsorption experiments showed very low levels of protein adsorption. Our findings suggest that the protein rejecting properties rely on a fine balance between the surface energy and/or hydrogen bond donating/accepting properties of the SAM surface.

  • 30.
    Horinek, Dominik
    et al.
    Technische Universität München.
    Serr, Andreas
    Technische Universität, München.
    Bonthuis, Douwe Jan
    Technische Universität München.
    Boström, Mathias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Kunz, Werner
    Universität Regensburg.
    Netz, Roland r.
    Technische Universität München.
    Molecular Hydrophobic Attraction and Ion-Specific Effects Studied by Molecular Dynamics2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, p. 1271-1283Article in journal (Refereed)
    Abstract [en]

       

  • 31.
    Imar, Shahzad
    et al.
    Dundalk Institute Technology, Ireland.
    Maccato, Chiara
    University of Padua, Italy.
    Dickinson, Calum
    University of Limerick, Ireland.
    Laffir, Fathima
    University of Limerick, Ireland.
    Vagin, Mikhail
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    McCormac, Timothy
    Dundalk Institute Technology, Ireland.
    Enhancement of Nitrite and Nitrate Electrocatalytic Reduction through the Employment of Self-Assembled Layers of Nickel- and Copper-Substituted Crown-Type Heteropolyanions2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 8, p. 2584-2592Article in journal (Refereed)
    Abstract [en]

    Multilayer assemblies of two crown-type type heteropolyanions (HPA), [Cu20Cl(OH)(24)(H2O)(12)(P8W48O184)](25-) and Ni-4(P8W48O148)(WO2)](28-), have been immobilized onto glassy carbon electrode surfaces via the layer-by-layer (LBL) technique employing polycathion-stabilized silver nanoparticles (AgNP) as the cationic layer within the resulting thin films characterized by electrochemical and physical methods. The redox behaviors of both HPA monitored during LBL assembly with cyclic voltammetry and impedance spectroscopy revealed significant changes by immobilization. The presence of AgNPs led to the retention of film porosity and electronic conductivity, which has been shown with impedance and voltammeric studies of film permeabilities toward reversible redox probes. The resulting films have been characterized by physical methods. Finally, the electrocatalytic performance of obtained films with respect to nitrite and nitrate electrocatalytic reduction has been comparatively studied for both catalysts. Nickel atoms trapped inside HPA exhibited a higher specific activity for reduction.

  • 32.
    Johansson, Emma
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Ballem, Mohamed
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Cordoba Gallego, Jose Manuel
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 8, p. 4994-4999Article in journal (Refereed)
    Abstract [en]

    Dispersed SBA-15 rods have been synthesized with varying lengths, widths, and pore sizes in a low-temperature synthesis in the presence of heptane and NH4F. The pore size of the material can systematically be varied between 11 and 17 nm using different hydrothermal treatment times And/or temperatures. The particle length (400-600 nm) and width (100-400 nm) were tuned by varying the HCl concentration. All the synthesized materials possess a large surface area of 400-600 m(2)/g And a pore volume of 1.05-1.30 cm(3). A, mechanism for the effect of the HCl concentration on the particle morphology is suggested. Furthermore, it is shown that the reaction time an be decreased to 1 h, with well-retained pore size and morphology. This work has resulted in SBA-15 rods with the largest pore size reported for this morphology.

  • 33.
    Kanmert, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Enocsson, Helena
    Linköping University, Department of Clinical and Experimental Medicine, Rheumatology. Linköping University, Faculty of Science & Engineering.
    Wetterö, Jonas
    Linköping University, Department of Clinical and Experimental Medicine, Rheumatology. Linköping University, Faculty of Health Sciences.
    Kastbom, Alf
    Linköping University, Department of Clinical and Experimental Medicine, Rheumatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Department of Rheumatology in Östergötland.
    Skogh, Thomas
    Linköping University, Department of Clinical and Experimental Medicine, Rheumatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Department of Rheumatology in Östergötland.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Designed Surface with Tunable IgG Density as an in Vitro Model for Immune Complex Mediated Stimulation of Leukocytes2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 5, p. 3493-3497Article in journal (Refereed)
    Abstract [en]

    We present the design of an in vitro for immune-complex-mediated stimulation of leukocytes and its functional characteristics with respect to monocyte adhesion. The model was based on orientation-controlled immobilization of a humanized IgG1 monoclonal antibody (rituximab) via its interaction with a biotinylated peptide epitope derived from the CD20 marker. The peptide was linked to neutravidin covalently attached to it mixed self-assembled monolayer of carboxyl- and methoxy-terminated oligo(ethylene glycol) alkane thiolates on gold. The surface adhesion propensity of human monocytes (cell line U917) was highly dependent on the lateral IgG density and indicated that there exists a distance between IgG-Fc on the surface where interactions with Fc gamma receptors are optimal. This well-defined platform allows for a careful control of the size and orientation of artificial IgG immune complexes, it is easily made compatible with, for example, cellular imaging, and it will become useful for in vitro studies on the importance of Fc gamma receptor interactions in chronic immune-mediated diseases.

  • 34.
    Karlsson, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Mårtensson, Lars-Göran
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Jonsson, Bengt-Harald
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Carlsson, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Adsorption of human carbonic anhydrase II variants to silica nanoparticles occur stepwise: binding is followed by successive conformational changes to a molten-globule-like state2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, no 22, p. 8470-8479Article in journal (Refereed)
    Abstract [en]

    The surface adsorption behavior of protein variants of the enzyme human carbonic anhydrase II (HCA II) to silica nanoparticles has been investigated. Various destabilized mutants were produced by site-directed mutagenesis of amino acids located in the interior of the protein. The silica particles induced a molten-globule-like state in all of the variants. All protein variants initially adsorbed to the particles, and then underwent conformational rearrangements in a stepwise manner, as indicated by the loss of activity and the subsequent loss of tertiary structure. Activity, CD, and ANS fluorescence measurements showed that a decrease in the global stability of the protein is strongly correlated to increased rates of conformational change following particle adsorption. In contrast to unfolding processes induced by chemical denaturants or heat, in the transition to the molten-globule-like state induced by the silica particles, the active site region unfolds before the majority of the tertiary interactions are broken.

  • 35.
    Koenig, Meike
    et al.
    Leibniz Inst Polymerforsch Dresden eV, Germany; Karlsruhe Inst Technol, Germany.
    Rodenhausen, Keith Brian
    Univ Nebraska Lincoln, NE 68588 USA; Biolin Sci Inc, NJ 07652 USA.
    Rauch, Sebastian
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Bittrich, Eva
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Eichhorn, Klaus-Jochen
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Nebraska Lincoln, NE 68588 USA.
    Stamm, Manfred
    Leibniz Inst Polymerforsch Dresden eV, Germany; Tech Univ Dresden, Germany.
    Uhlmann, Petra
    Leibniz Inst Polymerforsch Dresden eV, Germany; Univ Nebraska Lincoln, NE 68588 USA.
    Salt Sensitivity of the Thermoresponsive Behavior of PNIPAAm Brushes2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 7, p. 2448-2454Article in journal (Refereed)
    Abstract [en]

    We report investigations on the salt sensitivity of the thermoresponsive behavior of PNIPAAm brushes applying the quartz crystal microbalance coupled with spectroscopic ellipsometry technique. This approach enables a detailed study of the optical and mechanical behavior of the polymer coatings. Additional conclusions can be drawn from the difference between both techniques due to a difference in the contrast mechanism of both methods. A linear shift of the phase transition temperature to lower temperatures with the addition of sodium chloride was found, similar to the behavior of free polymer chains in solution. The thermal hysteresis was found to be decreased by the addition of sodium chloride to the solution, hinting to the interaction of the ions with the amide groups of the polymer, whereby the formation of hydrogen bonds is hindered. The results of this study are of relevance to the application of PNIPAAm brushes in biological fluids and demonstrate the additional potential of the ion sensitivity besides the better known thermosensitivity.

  • 36.
    Larsson (Kaiser), Andréas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Poly(ethylene glycol) gradient for biochip development2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 22, p. 11319-11325Article in journal (Refereed)
    Abstract [en]

    A novel method of producing a poly(ethylene glycol) (PEG)-based gradient matrix that varies gradually in thickness from 0 to 500 Å over a distance of 5−20 mm is presented. The gradient matrix is graft copolymerized from a mixture of PEG methacrylates onto organic thin films providing free radical polymerization sites initiated by UV irradiation at 254 nm. The films used as grafting platforms consist of either a spin-coated cycloolefin polymer or a self-assembled monolayer on planar gold. The thickness/irradiation gradient is realized by means of a moving shutter that slowly uncovers the modified gold substrate. The structural and functional characteristics of the gradient matrix are investigated with respect to thickness profile, degree of carboxylation, and subsequent immobilization of two model proteins of different sizes and shapes. These characteristics are studied with ellipsometry and infrared reflection−absorption microscopy using a grazing angle objective. It is revealed that the relatively small carboxylation agent used offers homogeneous activation throughout the gradient, even in the thick areas, whereas the diffusion/interpenetration and subsequent immobilization of large proteins is partially hindered. This is crucial information in biosensor design that can be easily obtained from a gradient experiment on a single sample. Moreover, the partially hindered protein interpenetration, the marginal swelling upon hydration, and the unspecific nature of the graft polymerization suggest a matrix growth mechanism that favors the formation of a bushlike polymer structure with a certain degree of cross linking.

  • 37.
    Lee, Hung-Hsun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ruzele, Zivile
    Institute Phys, Department Funct Nanomat, LT-02300 Vilnius, Lithuania .
    Malysheva, Lyuba
    Bogolyubov Institute Theoret Phys, UA-03143 Kiev, Ukraine .
    Onipko, Alexander
    Bogolyubov Institute Theoret Phys, UA-03143 Kiev, Ukraine .
    Gutes, Albert
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Valiokas, Ramunas
    Institute Phys, Department Funct Nanomat, LT-02300 Vilnius, Lithuania .
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Long-Chain Alkylthiol Assemblies Containing Buried In-Plane Stabilizing Architectures2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 24, p. 13959-13971Article in journal (Refereed)
    Abstract [en]

    A series of alkylthiol compounds were synthesized to study the formation and structure of complex self-assembled monolayers (SAMs) consisting of interchanging structural modules stabilized by intermolecular hydrogen bonds. The chemical structure of the synthesized compounds, HS(CH2)(15)CONH(CH2CH2O)(6)CH2CONH-X, where X refers to the extended chains of either -(CH2)(n)CH3 or -(CD2)(n)CD3, with n = 0, 1, 7, 8, 15, was confirmed by NMR and elemental analysis. The formation of highly ordered, methyl-terminated SAMs oil gold from diluted ethanolic solutions of these compounds was revealed using contact angle goniometry, mill ellipsometry, cyclic voltammetry, and infrared reflection absorption spectroscopy. The experimental work was complemented with extensive DFT modeling of infrared spectra and molecular orientation. New assignments were introduced for both nondeuterated and deuterated Compounds. The latter set of compounds also served as a convenient tool to resolve the packing, conformation, and orientation of the buried and extended modules within the SAM. Thus, it was shown that the lower alkyl portion together with the hexa(ethylene glycol) portion is stabilized by the two layers of lateral hydrogen bonding networks between the amide groups, and they provide it Structurally robust support for the extended alkyls, The presented system can be considered to be an extension of the well-known alkyl SAM platform, enabling precise engineering of nanoscopic architectures oil the length scale from a Few to similar to 60 angstrom for applications such as cell membrane mimetics, molecular nanolithography, and so forth.

  • 38.
    Lettieri, Raffaella
    et al.
    University of Roma Tor Vergata, Italy.
    Di Giorgio, Floriana
    University of Roma Tor Vergata, Italy.
    Colella, Alessandra
    University of Roma Tor Vergata, Italy.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Björefors, Fredrik
    Uppsala University, Sweden.
    Placidi, Ernesto
    University of Roma Tor Vergata, Italy.
    Palleschi, Antonio
    University of Roma Tor Vergata, Italy.
    Venanzi, Mariano
    University of Roma Tor Vergata, Italy.
    Gatto, Emanuela
    University of Roma Tor Vergata, Italy.
    DPPTE Thiolipid Self-Assembled Monolayer: A Critical Assay2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 44, p. 11560-11572Article in journal (Refereed)
    Abstract [en]

    Supported lipid membranes represent an elegant way to design a fluid interface able to mimic the physicochemical properties of biological membranes, with potential biotechnological applications. In this work, a diacyl phospholipid, the 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE), functionalized with a thiol group, was immobilized on a gold surface. In this molecule, the thiol group, responsible for the Au S bond (45 kJ/mol) is located on the phospholipid polar head, letting the hydrophobic chain protrude from the film. This system is widely used in the literature but is no less challenging, since its characterization is not complete, as several discordant data have been obtained. In this work, the film was characterized by cyclic voltammetry blocking experiments, to verify the SAM formation, and by reductive desorption measurements, to estimate the molecular density of DPPTE on the gold surface. This value has been compared to that obtained by quartz crystal microbalance measurements. Ellipsometry and impedance spectroscopy measurements have been performed to obtain information about the monolayer thickness and capacitance. The film morphology was investigated by atomic force microscopy. Finally, Monte Carlo simulations were carried out, in order to gain molecular information about the morphologies of the DPPTE SAM and compare them to the experimental results. We demonstrate that DPPTE molecules, incubated 18 h below the phase transition temperature (T = 41.1 +/- 0.4 degrees C) in ethanol solution, are able to form a self-assembled monolayer on the gold surface, with domain structures of different order, which have never been reported before. Our results make possible rationalization of the scattered results so far obtained on this system, giving a new insight into the formation of phospholipids SAMs on a gold surface.

  • 39. Lima, E. R. A.
    et al.
    Biscaia, E. C., Jr.
    Boström, Mathias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Tavares, F. W.
    Ion-specific forces between a colloidal nanoprobe and a charged surface2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 14, p. 7456-7458Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of ion-specific potentials on the force between a nanoprobe attached to a cantilever tip, and a charged surface. The probe is treated as a spherical nanoparticle with constant charge. A modified Poisson-Boltzmann equation in bispherical coordinates is used to address this problem in a more quantitative way. We predict that the ion-specific series of measured forces depend on the sign and magnitude of surface charge densities.

  • 40.
    Lima, E. R. A.
    et al.
    Escola de Quý´mica Universidade Federal do Rio de Janeiro.
    Boström, Mathias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Horinek, D.
    Technische Universität München..
    Biscaia, Jr, E. C.
    Universidade Federal do Rio de Janeiro.
    Kunz,, W.
    University of Regensburg..
    F. W. Tavares, F. W.
    Universidade Federal do Rio de Janeiro..
    Co-Ion and Ion Competition Effects: Ion Distributions Close to a Hydrophobic Solid Surface in Mixed Electrolyte Solutions2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, p. 3944-3948Article in journal (Refereed)
  • 41.
    Lundqvist, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Andrésen, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Christensson, Sara
    Department of Occupational and Environmental Medicine, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
    Johansson, Sara
    Department of Occupational and Environmental Medicine, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
    Karlsson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Broo, Klas
    Department of Occupational and Environmental Medicine, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
    Jonsson, Bengt-Harald
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Proteolytic cleavage reveals interaction patterns between silica nanoparticles and two variants of human carbonic anhydrase2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 25, p. 11903-11906Article in journal (Refereed)
    Abstract [en]

    To characterize the sites on the protein surface that are involved in the adsorption to silica nanoparticles and the subsequent rearrangements of the protein/nanoparticle interaction, a novel approach has been used. After incubation of protein with silica nanoparticles for 2 or 16 h, the protein was cleaved with trypsin and the peptide fragments were analyzed with mass spectrometry. The nanoparticle surface area was in 16-fold excess over available protein surface to minimize the probability that the initial binding would be affected by other protein molecules. When the fragment patterns obtained in the presence and absence of silica nanoparticles were compared, we were able to characterize the protein fragments that interact with the surface. This approach has allowed us to identify the initial binding sites on the protein structure and the rearrangement of the binding sites that occur upon prolonged incubation with the surface.

  • 42.
    Lundqvist, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Sethson, Ingmar
    Department of Organic Chemistry, Umeå University, Umeå, Sweden.
    Jonsson, Bengt-Harald
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    High-Resolution 2D 1H−15N NMR Characterization of Persistent Structural Alterations of Proteins Induced by Interactions with Silica Nanoparticles2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 13, p. 5974-5979Article in journal (Refereed)
    Abstract [en]

    The binding of protein to solid surfaces often induces changes in the structure, and to investigate these matters we have selected two different protein−nanoparticle systems. The first system concerns the enzyme human carbonic anhydrase II which binds essentially irreversibly to the nanoparticles, and the second system concerns human carbonic anhydrase I which alternate between the adsorbed and free state upon interaction with nanoparticles. Application of the TROSY pulse sequence has allowed high-resolution NMR analysis for both of the protein−nanoparticle systems. For HCAII it was possible to observe spectra of protein when bound to the nanoparticles. The results indicated that HCAII undergoes large rearrangements, forming an ensemble of molten globule-like structures on the surface. The spectra from the HCAI−nanoparticle system are dominated by HCAI molecules in solution. A comparative analysis of variations in intensity from 97 amide resonances in a 1H−15N TROSY spectrum revealed the effects from interaction with nanoparticle on the protein structure at amino acid resolution.

  • 43.
    Lundqvist, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Sethson, Ingmar
    Department of Organic Chemistry, Umeå University, Umeå, Sweden.
    Jonsson, Bengt-Harald
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Protein adsorption onto silica nanoparticles: conformational changes depend on the particles' curvature and the protein stability2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 24, p. 10639-10647Article in journal (Refereed)
    Abstract [en]

    We have analyzed the adsorption of protein to the surfaces of silica nanoparticles with diameters of 6, 9, and 15 nm. The effects upon adsorption on variants of human carbonic anhydrase with differing conformational stabilities have been monitored using methods that give complementary information, i.e., circular dichroism (CD), nuclear magnetic resonance (NMR), analytical ultracentrifugation (AUC), and gel permeation chromatography. Human carbonic anhydrase I (HCAI), which is the most stable of the protein variants, establishes a dynamic equilibrium between bound and unbound protein following mixture with silica particles. Gel permeation and AUC experiments indicate that the residence time of HCAI is on the order of 10 min and slowly increases with time, which allows us to study the effects of the interaction with the solid surface on the protein structure in more detail than would be possible for a process with faster kinetics. The effects on the protein conformation from the interaction have been characterized using CD and NMR measurements. This study shows that differences in particle curvature strongly influence the amount of the protein's secondary structure that is perturbed. Particles with a longer diameter allow formation of larger particle−protein interaction surfaces and cause larger perturbations of the protein's secondary structure upon interaction. In contrast, the effects on the tertiary structure seem to be independent of the particles' curvature.

  • 44.
    Mak, Wing Cheung
    et al.
    Hong Kong University of Science and Technology, Hong Kong, China .
    Bai, Jianhao
    National University of Singapore.
    Chang, Xiang Yun
    National University of Singapore.
    Trau, Dieter
    National University of Singapore.
    Matrix-assisted colloidosome reverse-phase layer-by-layer encapsulating biomolecules in hydrogel microcapsules with extremely high efficiency and retention stability2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 2, p. 769-775Article in journal (Refereed)
    Abstract [en]

    The layer-by-layer (LbL) polyelectrolyte self-assembly encapsulation method has attracted much interest because of its versatility to use various polymers for capsule formation, ability to encapsulate different templates, and capability to control capsule permeability. Traditionally, the LbL method was performed in water as solvent and limited to poorly or non-water-soluble templates. Using the matrix-assisted LbL method, complex mixtures of water-soluble proteins or DNA could be encapsulated within agarose microbeads templates but leakage of biomolecules into the water phase during the LbL process results in low encapsulation efficiency. Recently, the reverse-phase LbL (RP-LbL) method was introduced to perform LbL and encapsulation of water-soluble templates in organic solvents, thus preventing the templates from dissolving and allowing high encapsulation efficiency. However, encapsulation of complex mixtures of biomolecules or other substances with quantitative encapsulation efficiency remained impossible. Here we present a new approach for encapsulation of biomolecules or complex mixtures thereof with almost 100% encapsulation efficiency. The ability of our method to achieve high encapsulation efficiency arises from the combination of two strategies. (1) Using microparticles as surface stabilizer to create stable biomolecule-loaded hydrogel microbeads, termed matrix-assisted colloidosome (MAC), that are able to disperse in oil and organic solvents. (2) Using the RP-LbL method to fabricate polymeric capsule “membranes”, thereby preventing diffusion of the highly water-soluble biomolecules. Using an oil phase during emulsification and an organic solvent phase during encapsulation could completely prevent leakage of water-soluble biomolecules and almost 100% encapsulation efficiency is achieved. Microcapsules fabricated with our method retained nearly 100% of encapsulated proteins during a 7 day incubation period in water. The method was demonstrated on model proteins and may be extended to other biomolecules or mixtures. Our method is a valuable addition to the family of encapsulation techniques and can significantly contribute to the fields of bioreactors and bioanalytical microcapsules.

  • 45.
    Martinez, Jose G.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology. Technical University of Cartagena. Spain.
    Otero, Toribio F.
    Technical University of Cartagena. Spain.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Effect of the Electrolyte Concentration and Substrate on Conducting Polymer Actuators2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 13, p. 3894-3904Article in journal (Refereed)
    Abstract [en]

    The effect of the electrolyte concentration (NaCl aqueous electrolyte) on the dimensional variations of films of polypyrrole doped with dodecylbenzenesulfonate PPy(DBS) on Pt and Au wires was studied. Any parallel reaction that occurs during the redox polymeric reaction that drives the mechanical actuation, as detected from the coulovoltammetric responses, was avoided by using Pt wires as substrate and controlling the potential limits, thus significantly increasing the actuator lifetime. The NaCl concentration of the electrolyte, when studied by cyclic voltammetry or chronoamperometry, has a strong effect on the performance as well. A maximum expansion was achieved in 0.3 M aqueous solution. The consumed oxidation and reduction charges control the fully reversible dimensional variations: PPy(DBS) films are faradaic polymeric motors. Parallel to the faradaic exchange of the cations, osmotic, electrophoretic, and structural changes play an important role for the water exchange and volume change of PPy(DBS).

  • 46.
    Miklavcic, Stan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    White, L.R.
    Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA.
    Stable van der Waals-induced deformations of the air-water interface. Theoretical predictions and a suggestion for an experiment2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 16, p. 6961-6968Article in journal (Refereed)
    Abstract [en]

    This article concerns the stability of the air-water interface subjected to a 2D attractive van der Waals stress. The physical problem models the setup of a Wilhelmy plate experiment prior to three-phase contact line formation. We present and employ an unambiguous condition to quantify the stability limit in terms of the distance of closest approach of a solid cylindrical plate of parabolic cross section to the fluid surface as a function of the strength of the van der Waals surface force and plate geometry. A numerical study spanning 4 orders of magnitude of the Hamaker constant and nearly 6 orders of magnitude of solid geometry characterizes the dependence of the stability limit on these physical parameters. Comparisons are also made with a previously published analytical condition guaranteeing a stable deformation of the fluid interface. A possible experiment for testing the theory is also described. Used together with the theory, the technique could be used as an independent means of determining system properties such as the surface tension or Hamaker constant. © 2006 American Chemical Society.

  • 47.
    Myrskog, Annica
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Anderson, Henrik
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden/Uppsala University, Ångström Laboratory, Solid State Electronics, P.O. Box 534, SE-751 21 Uppsala, Sweden.
    Ingemarsson, Björn
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Esterification of self-assembled carboxylic acid-terminated thiolmonolayers in acid environment: A time dependent study2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 2, p. 821-829Article in journal (Refereed)
    Abstract [en]

    This contribution reports on the influence of acids on the quality of carboxylic acid terminated self-assembled monolayers (SAMs) on gold prepared from ethanolic solution of HS-(CH2)15-COOH and HS-(CH2)11CONH–(EG)6CH2-COOH. Null ellipsometry, contact angle goniometry and infrared reflection-absorption spectroscopy are used to monitor the physical and chemical changes occurring within the SAMs upon acid post treatment; after incubation with acids present in the solution; and after incubation in aged acid containing solutions. The presence of acid has a positive effect on the crystallinity, packing and orientation of the supporting alkyl and ethylene glycol subunits of the SAM. Our studies also confirm previous findings stating that the carboxylic groups are rapidly converted into ethyl ester groups in the presence of hydrochloric acid in the incubation solution. It is also evident that the conversion occurs in the presence of the weaker acid, acetic acid, although at a much slower rate than for hydrochloric acid. This is a new observation that has not been reported on before. The physical and chemical characterization is also complemented with a functional bioaffinity study. The functional evaluation revealed that the present model system was surprisingly insensitive to the degree of esterification of the carboxylic acid SAMs, but that 4 weeks of storage of the two investigated thiols in hydrochloric acid containing ethanol resulted in SAMs that were completely inactive with respect to immobilization and subsequent binding of the antigen. It was encouraging to note that the non-specific binding of both antigen and antibody was extremely low on the two SAMs, regardless of the relative amount of ethyl esters on the surface.

  • 48.
    Olin, Pontus
    et al.
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Lindström, Stefan B.
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    Pettersson, Torbjörn
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Wågberg, Lars
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Water drop friction on superhydrophobic surfaces2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 29, p. 9079-9089Article in journal (Refereed)
    Abstract [en]

    To investigate water drop friction on superhydrophobic surfaces, the motion of water drops on three different superhydrophobic surfaces has been studied by allowing drops to slide down an incline and capturing their motion using high-speed video. Two surfaces were prepared using crystallization of an alkyl ketene dimer (AKD) wax, and the third surface was the leaf of a Lotus (Nelumbo Nucifera). The acceleration of the water droplets on these superhydrophobic surfaces was measured as a function of droplet size and inclination of the surface. For small capillary numbers, we propose that the energy dissipation is dominated by intermittent pinning–depinning transitions at microscopic pinning sites along the trailing contact line of the drop, while at capillary numbers exceeding a critical value, energy dissipation is dominated by circulatory flow in the vicinity of the contacting disc between the droplet and the surface. By combining the results of the droplet acceleration with a theoretical model based on energy dissipation, we have introduced a material-specific coefficient called the superhydrophobic sliding resistance, bsh. Once determined, this parameter is sufficient for predicting the motion of water drops on superhydrophobic surfaces of a general macroscopic topography. This theory also infers the existence of an equilibrium sliding angle, βeq, at which the drop acceleration is zero. This angle is decreasing with the radius of the drop and is in quantitative agreement with the measured tilt angles required for a stationary drop to start sliding down an incline.

  • 49.
    Olin, Pontus
    et al.
    KTH Royal Institute Technology, Sweden.
    Lindström, Stefan
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Wagberg, Lars
    KTH Royal Institute Technology, Sweden; KTH Royal Institute Technology, Sweden.
    Trapping of Water Drops by Line-Shaped Defects on Superhydrophobic Surfaces2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 23, p. 6367-6374Article in journal (Refereed)
    Abstract [en]

    We have investigated the effect of line-shaped topographical defects on the motion of water drops across superhydrophobic wax surfaces using a high-speed video camera. The defects are introduced onto the superhydrophobic wax surfaces by a scratching procedure. It is demonstrated that the motion of a drop interacting with the defect can be approximated by a damped harmonic oscillator. Whether a drop passes or gets trapped by the defect is determined by the incident speed and the properties of the oscillator, specifically by the damping ratio and a nondimensional forcing constant representing the effects of gravity and pinning forces. We also show that it is possible to predict a critical trapping speed as well as an exit speed in systems with negligible viscous dissipation using a simple work energy consideration.

  • 50.
    Parsons, D. F.
    et al.
    Research School of Physical Sciences and Engineering, Australian National University, Canberra.
    Boström, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Maceina, T. J.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Salis, A
    Department of Chemical Sciences, University of Cagliari - CSGI, Moserrato, Italy.
    Ninham, B. W.
    Research School of Physical Sciences and Engineering, Australian National University, Canberra.
    Why Direct or Reversed Hofmeister Series? Interplay of Hydration,Non-electrostatic Potentials, and Ion Size2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 5, p. 3323-3328Article in journal (Refereed)
    Abstract [en]

    A modified Poisson-Boltzmann analysis is made of the double layer interaction between two silica surfaces and twoalumina surfaces in chloride electrolyte. The analysis incorporates nonelectrostatic ion-surface dispersion interactionsbased on ab initio ionic excess polarizabilities with finite ion sizes. A hydration model for the tightly held hydration shellof kosmotropic ions is introduced. A direct Hofmeister series (K > Na > Li) is found at the silica surface while thereversed series (Li > Na > K) is found at alumina, bringing theory in line with experiment for the first time.Calculations with unhydrated ions also suggest that surface-induced dehydration may be occurring at the aluminasurface.

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