Protein Adsorption/Desorption Mediated By PH-responsive Poly- Mer Layer

We propose a new way of pH-regulated protein adsorption, which is mediated by a weak polyelectrolyte layer. According to theoretical results obtained from a molecular theory and kinetic approaches, both thermodynamics and kinetics of protein adsorp-tion are verified well controlled by the solution pH. The kinetics and the amount of adsorbed proteins at equilibrium are greatly increased from the acid environment to neutral surroundings. The reason is that the increased pH promotes the dissociation of the weak polyelectrolyte, resulting in more charged monomers and more stretched chains. Therefore, steric repulsion within the polymer layer is decreased, which effec-tively weakens the barrier felt by the protein during the process of adsorption. Interest-ingly, we also find the kinetics of protein desorption is almost changeless with the vari-ation of pH. Although the barrier formed by polymer layer changes with the change of pH, the potential of the surface with the adsorbed proteins varies equally, which makes their difference keep constant. It is the difference that determines the desorption rate, so protein desorption is not pH-regulated. Our results may provide useful insights into controllable protein adsorption/desorption in practical applications.