Surface chemistry of bovine serum albumin with hematite nanoparticles and its effect on arsenate adsorption

Environmental contextHematite nanoparticles are efficient adsorbents for proteins and pollutants in environmental and biological systems. Hematite and the protein bovine serum albumin (BSA) were used as models to investigate the surface chemistry and competitive role of BSA in arsenate adsorption. Results show that surface BSA inhibits arsenate adsorption, potentially altering its mobility and bioavailability. AbstractThe surface chemistry of metal oxide nanomaterials controls their health impacts and fate in environmental and biological systems. These systems contain proteins capable of binding to nanoparticles, which forms a protein corona that modifies the surface properties of the nanoparticles and reactivity towards pollutants. Using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, we investigate the adsorption of bovine serum albumin (BSA) and quantify the competitive effect of BSA on the adsorption kinetics of arsenate, AsV, to hematite nanoparticles. Experiments were conducted in the flow mode at pH 7. BSA was first adsorbed on hematite, then AsV was allowed to flow over the BSA/hematite thin film. Adsorption kinetic and thermodynamic parameters were calculated using a modified Langmuir adsorption model for both BSA and AsV. The adsorption thermodynamic model showed that BSA binds through two active sites with a binding energy of –41 kJ mol−1, which corresponds to the spontaneous formation of chemisorbed and physisorbed species. When AsV flowed over the BSA/hematite film, only 11 % of surface BSA was desorbed by AsV. This result highlights the inhibitory effect of BSA for AsV adsorption. Structural analysis of BSA revealed changes to the local conformational geometry upon adsorption to and desorption from hematite nanoparticles. Molecular docking simulations showed that the binding free energy of a modelled hematite nanoparticle towards the BSA surface is –6.8 kcal mol−1 (−28.5 kJ mol−1) owing to the formation of various bonds, which agrees with the adsorption kinetics modelling. Overall, surface BSA inhibits arsenate adsorption and therefore increases its mobility and bioavailability.