3 research outputs found

    Bovine Serum Albumin and Fibrinogen Adsorption at the 316L Stainless Steel/Aqueous Interface

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    The binding of bovine serum albumin (BSA) to a 316L stainless steel surface from a buffer solution has been characterized using neutron reflectometry and quartz crystal microbalance measurements; coverage at all concentrations up to a near-physiological concentration was found to be relatively low (<20%); the protein followed a two-step isotherm adsorption model type and the overall thickness at the higher concentrations (around 80 Ã…) suggested possible multilayering and/or protein unfolding. As it has been postulated that BSA may inhibit the further adsorption of another blood plasma proteinî—¸fibrinogenî—¸the effects of preadsorbing BSA on fibrinogen adsorption were examined, first by prior physisorption of BSA to the stainless steel surface and second by pretreating the stainless steel with a layer of sodium dodecyl sulfate (SDS) to render it more hydrophobic. Although the preadsorption of BSA to an untreated stainless steel surface did slightly decrease the amount of fibrinogen adsorbed initially, it had no inhibiting effect if a solution containing solely fibrinogen subsequently flowed through. In contrast, the SDS-treated surface yielded both an increased BSA adsorption and consistently decreased fibrinogen adsorption

    Response of Plasma-Polymerized Hexamethyldisiloxane Films to Aqueous Environments

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    Thin plasma polymer films were deposited in hexamethyldisiloxane (HMDSO) and HMDSO/O<sub>2</sub> low-pressure discharges and their chemical structures analyzed using infrared (IR) spectroscopy and neutron reflectometry (NR). The (plasma-polymerized) ppHMDSO film exhibits hydrophobic, poly­(dimethylsiloxane)-like properties, while the retention of carbon groups is reduced by O<sub>2</sub> addition, yielding a more inorganic, hydrophilic ppSiO<sub><i>x</i></sub> film. Both films show a minor (vertical) density gradient perpendicular to the substrate, where the exposed film surface seems to be more oxidized, indicating oxidative aging reactions upon contact with air. The hydration and water uptake abilities of the films in aqueous environments were investigated in humid environments using ellipsometry, NR in D<sub>2</sub>O, and multiple transmission-reflection IR measurements after equilibration of the films in water

    Semifluorinated Alkanes at the Air–Water Interface: Tailoring Structure and Rheology at the Molecular Scale

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    Semifluorinated alkanes form monolayers with interesting properties at the air–water interface due to their pronounced amphi-solvophobic nature and the stiffness of the fluorocarbons. In the present work, using a combination of structural and dynamic probes, we investigated how small molecular changes can be used to control the properties of such an interface, in particular its organization, rheology, and reversibility during compression–expansion cycles. Starting from a reference system perfluor­(dodecyl)­dodecane, we first retained the linear structure but changed the linkage groups between the alkyl chains and the fluorocarbons, by introducing either a phenyl group or two oxygens. Next, the molecular structure was changed from linear to branched, with four side chains (two fluorocarbons and two hydrocarbons) connected to extended aromatic cores. Neutron reflectivity at the air–water interface and scanning force microscopy on deposited films show how the changes in the molecular structure affect molecular arrangement relative to the interface. Rheological and compression–expansion measurements demonstrate the significant consequences of these changes in molecular structure and interactions on the interfacial properties. Remarkably, even with these simple molecules, a wide range of surface rheological behaviors can be engineered, from viscous over viscoelastic to brittle solids, for very similar values of the surface pressure
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