Abstract
Surface interactions with polymers or proteins are extensively studied in a range of industrial and biomedical applications to control surface modification, cleaning, or biofilm formation. In this study we compare surfactant interactions with protein-coated silica surfaces differing in the degree of curvature (macroscopically flat and colloidal nanometric spheres). The interaction with a flat surface was probed by means of surface plasmon resonance (SPR) while dynamic light scattering (DLS) was used to study the interaction with colloidal SiO2 (radius 15 nm). First, the adsorption of bovine serum albumin (BSA) with both SiO2 surfaces to create a monolayer of coating protein was studied. Subsequently, the interaction of these BSA-coated surfaces with a non-ionic surfactant (a decanol ethoxylated with an average number of eight ethoxy groups) was investigated. A fair comparison between the results obtained by these two techniques on different geometries required the correction of SPR data for bound water and DLS results for particle curvature. Thus, the treated data have excellent quantitative agreement independently of the geometry of the surface suggesting the formation of multilayers of C10PEG over the protein coating. The results also show a marked different affinity of the surfactant towards BSA when the protein is deposited on a flat surface or individually dissolved in solution.
Highlights
Protein/surfactant interactions find important applications in industry and science
The latter value coincides with the ζ-potential measured for bovine serum albumin (BSA) in the same buffer and, strongly supports the scenario that under these conditions the system is formed by glass beads coated by BSA and represents the colloidal counterpart of the macroscopic silica surface covered by 450 ng/cm2 of BSA
The data obtained by means of surface plasmon resonance (SPR) and dynamic light scattering (DLS) indicate a strong affinity of the non-ionic surfactant for the BSA-coated surfaces that becomes an effective adsorption at concentrations well above the critical micelle concentration (CMC)
Summary
Protein/surfactant interactions find important applications in industry and science. Their behavior at the air/liquid or liquid/liquid interface has been widely investigated due to their importance in the formation and stabilization of foams and emulsions [1,2,3,4,5,6,7]. Studies of adsorption and protein/surfactant interaction at the liquid/solid interface are, not common. The subject of this paper is to investigate the potential use of colloidal surfaces instead of flat macromolecular ones for the research of interactions at the liquid/solid interface. The use of colloidal surfaces in combination with dynamic light scattering (DLS) could present many potential advantages since it can be applied to a wide range of materials including those that are unsuited for the external. We compare the results of the interactions common and relevant surfactant widely used in industry. We compare the results of both between solid-surface using surfaceusing plasmon resonance (SPR), dynamic light thebetween interactions both conformations solid‐surface conformations surface plasmon resonance (SPR), scattering (DLS), and laser.
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