3 research outputs found
Bovine Serum Albumin and Fibrinogen Adsorption at the 316L Stainless Steel/Aqueous Interface
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
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, polyÂ(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
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 perfluorÂ(dodecyl)Âdodecane, 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