Polyelectrolyte-nanoparticle mutual charge regulation and its influence on their complexation

The complexation between a charged nanoparticle and an oppositely charged linear polyelectrolyte is studied using coarse-grained Semi-Grand Canonical Monte Carlo simulations. This is done for systems where one or both of the macromolecules are titratable, i.e. they have a pH-dependent charge. The presence of charge fluctuation is found to have a significant impact on the ionization of both macromolecules, the conformational properties of the adsorbed polyelectrolyte and the charge of the resulting complex. When both macromolecules are titratable, we find that the impact is larger when the absolute difference in the pKa values of the nanoparticle and polyelectrolyte increases. The physicochemical concepts here discussed are found to be in good agreement with previous experimental observations, providing a fundamental basis to rationalize these experiments.