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

Abstract

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 Å) suggested possible multilayering and/or protein unfolding. As it has been postulated that BSA may inhibit the further adsorption of another blood plasma protein-fibrinogen-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.

Structural Changes in Adsorbed Cytochrome c upon Applied Potential Characterized by Neutron Reflectometry

“…When a Sauerbrey model is used to fit the data, a figure of approximately 4.0 × 10 –7 mol m –2 adsorbed protein is calculated for the 2 mg mL –1 sample at pH 7.4 at equilibrium and 4.6 × 10 –7 mol m –2 for the 2 mg mL –1 sample at pH 10. These figures are significantly higher than the values predicted by either the depletion isotherms or neutron reflectometry (Figure and Figure ) and may reflect both an underestimation of surface area (as the QCM-D sensor surfaces will have some roughness that is not accounted for in the calculations) and also the water associated with the adsorbed protein, which is detected by the QCM-D but not by the other techniques. ,,, …”

“…These figures are significantly higher than the values predicted by either the depletion isotherms or neutron reflectometry (Figure 2 and Figure 8) and may reflect both an underestimation of surface area (as the QCM-D sensor surfaces will have some roughness that is not accounted for in the calculations) and also the water associated with the adsorbed protein, which is detected by the QCM-D but not by the other techniques. 6,7,32,33 It is interesting that, although much higher concentrations were used than for the depletion isotherms (1 mg mL −1 is equivalent to approximately 8 × 10 −5 mol dm −3 ), there is still an increase in the frequency change and hence amount of protein adsorbed, between the 1 and 2 mg mL −1 protein samples. This may indicate that the Langmuir model shown in Figure 2 is not a true fit to the data at these higher concentrations.…”

“…Stainless steel and other metals have shown promise when used as anodes in MFCs; 316L stainless steel has been successfully studied before using NR , and was chosen as a model anode material that should remain relatively inert when exposed to electrolyte solution. The inert nature of the stainless steel arises from the outer surface oxide layer which, though comprising both iron and chromium oxides, is highly enriched in chromium compared to the bulk metal composition and hence more resistant to corrosion. − A larger, c-type cytochrome, OmcA, has been found to adsorb strongly to hematite (Fe 2 O 3 ) surfaces and retain redox activity for a given time, after which the conformation or orientation of the adsorbed protein was assumed to change as peaks in the cyclic voltammogram disappeared. , …”

“…3 As the heme redox center occupies a mere 0.6% of the exposed protein surface, correct orientation is critical in allowing electron transfer to occur between cytochrome c and its redox partners in its natural mitochondrial environment; changes to the charged surface groups even far away from the redox center can have a significant adverse effect on the electron transfer efficiency because of their contributions to the overall dipole moment. 4 Stainless steel and other metals have shown promise when used as anodes in MFCs; 5 316L stainless steel has been successfully studied before using NR 6,7 and was chosen as a model anode material that should remain relatively inert when exposed to electrolyte solution. The inert nature of the stainless steel arises from the outer surface oxide layer which, though comprising both iron and chromium oxides, is highly enriched in chromium compared to the bulk metal composition and hence more resistant to corrosion.…”

Studying Hemoglobin and a Bare Metal–Porphyrin Complex Immobilized on Functionalized Silicon Surfaces Using Synchrotron X-ray Reflectivity

“…Additionally, Si is also highly biocompatible. Proteins are biological substrates, and hence characterizing their interfaces with silicon help us in understanding biomaterial–protein interactions that may be of high relevance not only for design of biocompatible interfaces and biosensors but also have deep implications for fundamental understanding of related phenomenon in the realm of chemical biology. For meeting the study objectives, an organized layer of the protein on the Si substrate is essential.…”