Size-Dependent Protein Adsorption on a Nanoparticle.

This study presents the mechanism of adsorption of a model protein within an electrical double layer (EDL) of a charged silica NP in an aqueous salt medium. In contrast to previous works, the charge regulation model analyzes the surface chemistry and electrostatic charge within the EDL by considering polarization, morphology, topography, and protonation/deprotonation. This model is coupled with the three protein adsorption models, such as Classical Langmuir (CLM), Extended Langmuir (ELM), and Two-State (TSM). By this means, surface curvature, conformational changes, and size- and pH-dependent characteristics of protein adsorption are allowed to be observed together in the present numerical model. For a parametric investigation, ionic concentration and pH of the solution, surface charge density, initial protein concentration, electrostatic charge of the protein, and the diameter of the NP are varied systematically. The validation studies with the experimental data agree well with the literature. The size-dependent protein adsorption is simulated and revealed with the current numerical model. Space charge density, chemistry, and morphology of NP's surface profoundly influence adsorption characteristics.