Effects of Charge Regulation on the Conformations and Dynamics of a Polyelectrolyte during Nanoparticle Adsorption
Customizing the surface characteristics and stimuli-responsive behavior of polyelectrolyte (PE) during interaction with nanoparticles (NP) have potential applications ranging from biological interactions to advanced diagnostic technologies. Using numerical simulations, we investigate how charge regulation (CR) shapes the conformation, dynamics and adsorption of PE on a oppositely charged NP and compared the results with constant charge (CC) conditions. At low solvent ion concentrations, CR barely affects the adsorption fraction, while significantly enhancing the dynamical response of the PE. However, at high ion concentrations, while complexation is suppressed in the CC case, the CR environment helps to overcome the energy barriers related to Debye screening and thermal fluctuations, thereby promoting the adsorption. By maintaining the strong PE-NP electrostatic interaction, PE exhibits a more directed ballistic-like dynamics towards NP during adsorption, in comparison to the diffusive and sub-diffusive behavior observed in the CC case. Our results emphasize that in high ion concentrations, with a strong Debye screening effect, a small fraction of charge-fluctuating sites suffices for adsorption to happen. A tunable CR mechanism is thus an efficient and robust strategy to control the biomolecular interaction and stability in complex environments.