Coupled impact of proteins with different molecular weights and surface charges on TiO2 mobility

Abstract

The widely present proteins in the natural environment interact with released nanoparticles, which changes the stability, transport, and fate of nanoparticles. Since proteins with different molecular weights contain various amino acids, the surface properties of the protein are different, and the mechanisms that affect the stability and mobility of nanoparticles are also distinct. To date, the effects of proteins with different molecular weights and surface charges on nanoparticles have received little attention. In this study, the effects of concentrations and three different molecular weights of protein on the stability and mobility of TiO₂ nanoparticles are investigated. Our study found that with the increase in bovine serum albumin (BSA) concentration from 2 to 16 mg L⁻¹ and the decrease in molecular weight of the proteins from 68 to 14 kDa, the capacity for protein adsorption on the TiO₂ surface was increased, and the thickness of the protein adsorption layer was increased too, causing stronger steric repulsive interactions. For proteins with different molecular weights and negative surface charges, the thickness of the protein adsorption layer is the dominant factor for TiO₂ stability, and both steric and electrostatic repulsion play critical roles in TiO₂ mobility. This study emphasized that the steric repulsion induced by the thickness of the protein adsorption layer increased nanoparticle stability in an aqueous environment, and the coupled impact of steric and electrostatic repulsion due to different molecular weights and negative surface charges of proteins strongly affects nanoparticle mobility in a saturated porous medium.