Effects of salt on the size and internal structure of PAMAM dendrimers at different pH

G4 and G5 polyamidoamine dendrimers solvated with explicit water, counterions and NaCl ions (0.15, 1 M) were simulated at two levels of protonation, which mimic their electrostatic charges at pH 5 and 7. We used the previously parametrised coarse-grained dendrimer model which had predicted the experimentally measured and theoretically calculated size and internal structure of the dendrimer at different pH values. In this study, addition of ≤ 1 M NaCl does not significantly modulate the dendrimer size, in agreement with experiments and other theoretical studies. In particular, added salt ions do not change the dense-shell and dense-core structures of dendrimers without salt, respectively, at pH 5 and 7. Besides counterions, only a few excess ions penetrate and occupy the dendrimer interior, leading to unchanged volume of the inner cavity in the dendrimer core. These results indicate that addition of ≤ 1 M NaCl does not modulate the efficiency of encapsulating hydrophobic drugs or compounds.