A comparative PM-IRRAS and ellipsometry study of the adsorptive behaviour of bovine serum albumin on a gold surface

In situ Fourier transform infrared-attenuated total reflection spectroscopy and modeling investigation of protein adsorption: Case of expanded bovine serum albumin on titanium dioxide anatase

The purpose of this experimental and modeling research is to study the pH effect and to determine the surface coverage plus the adsorption constant (Ka) of bovine serum albumin (BSA) protein adsorbed on TiO2 anatase surface, respectively. In situ Fourier transform infrared-attenuated total reflection spectroscopy in a flow-through cell was used to study the BSA adsorption on porous TiO2 anatase films. The experiments were performed in water solution, under different pH values, at a concentration of 10-6 mol/l. Theoretically, we extended the two-state model, based on a system of coupled differential equations, by adding a desorption parameter Kd2, for unfolded state. The model was solved taking into account the adsorption (Ka), desorption (Kd1,2), transformation (Kf) coefficients, and the initial solution protein concentration (C0). The findings clearly illustrated that the solution pH drastically changed the behavior of BSA adsorption, whereas the mathematical analytical solutions allowed us to determine the native state (θ1), the unfolded state (θ2), and the full one (θ) surface coverages. Finally, a good application of the approximated model on the experimental work, expanded BSA adsorbed on TiO2 anatase at pH = 1.7, indicated a value of Ka = (408.36 ± 0.996) × 102 mol-1 l min-1.

Functionalized Parylene Films for Enhancement of Antibody Production by Hybridoma Cells

In this study, the influence of microenvironments on antibody production of hybridoma cells was analyzed using six types of functionalized parylene films, parylene-N and parylene-C (before and after UV radiation), parylene-AM, and parylene-H, and using polystyrene as a negative control. Hybridoma cells were cultured on modified parylene films that produced a monoclonal antibody against the well-known fungal toxin ochratoxin-A. Surface properties were analyzed for each parylene film, such as roughness, chemical functional groups, and hydrophilicity. The proliferation rate of the hybridoma cells was observed for each parylene film by counting the number of adherent cells, and the total amount of produced antibodies from different parylene films was estimated using indirect ELISA. In comparison with the polystyrene, the antibody-production by parylene-H and parylene-AM was estimated to be observed to be as high as 210-244% after the culture of 24 h. These results indicate that the chemical functional groups of the culture plate could influence antibody production. To analyze the influence of the microenvironments of the modified parylene films, we performed cell cycle analysis to estimate the ratio of the G0/G1, S, and G2/M phases of the hybridoma cells on each parylene film. From the normalized proportion of phases of the cell cycle, the difference in antibody production from different surfaces was considered to result from the difference in the proliferation rate of hybridoma cells, which occurred from the different physical and chemical properties of the parylene films. Finally, protein expression was analyzed using an mRNA array to determine the effect of parylene films on protein expression in hybridoma cells. The expression of three antibody production-related genes (CD40, Sox4, and RelB) was analyzed in hybridoma cells cultured on modified parylene films.

Effect of carbamylation on protein structure and adsorption to self-assembled monolayer surfaces

Protein adsorption research has primarily focused upon the effects of surface chemistry, with almost no emphasis on how changes to proteins that occur in various disease states may influence their adsorption. One such situation occurs with chronic kidney disease where, despite hemodialysis treatment, the retention of urea within the blood compartment leads to protein carbamylation. Protein carbamylation has been shown to alter the function and structure of proteins. This work is focused on understanding how different degrees of carbamylation affect the physicochemical properties (structure, charge, water interactions) of single proteins (α-lactalbumin, albumin, and fibrinogen) and their adsorption to self-assembled monolayers. It was found that, unlike its secondary structure, the protein's tertiary structure was significantly altered upon carbamylation. Also, compared to native proteins, an increase in carbamylation lead to an increase in the negative surface charge of the protein and a weaker hydration state of the protein. In order to study the effects of different types of neutral surfaces, of different surface-water properties, on protein adsorption both bare and alkanethiol modified (-CH₃ or -OH end-groups) Au surfaces with were used as model surfaces. A significant decrease in adsorbed amounts of carbamylated fibrinogen and carbamylated α-lactalbumin, but not for carbamylated albumin, relative to native proteins was observed for both surfaces; suggesting that the increase in negative surface charge is more influential on adsorption than the change in hydration that occurs throughout the protein upon carbamylation. This data suggests that protein alterations that occur due to disease states have a significant effect on the overall protein structure and these changes affect their adsorption to surfaces.

Immobilized enzymes: understanding enzyme – surface interactions at the molecular level

Interactions between immobilized enzymes and supporting surfaces are complex and context-dependent and can significantly alter enzyme structure, stability and activity.