Nanoparticle Adsorption on a Weak Polyelectrolyte. Stiffness, pH, Charge Mobility, and Ionic Concentration Effects Investigated by Monte Carlo Simulations

Abstract

Monte Carlo simulations have been used to study two different models for a weak linear polyelectrolyte in the presence of nanoparticles: (i) a rodlike and (ii) a flexible polyelectrolytes. The use of simulated annealing has made it possible to simulate a polyelectrolyte chain in the presence of several nanoparticles by improving conformation sampling and avoiding multiple minima problems when dense conformations are produced. Nanoparticle distributions along the polymer backbone were analyzed versus the ionic concentration, polyelectrolyte stiffness, and nanoparticle surface charge. Titration curves were calculated and the influences of the ionic concentration, solution pH, and number of adsorbed nanoparticles on the acid/base polyelectrolyte properties have been systematically investigated. The subtle balance of attractive and repulsive interactions has been discussed, and some characteristic conformations are presented. The comparison of the two limit models provides a good representation of the stiffness influence on the complex formation. In some conditions, overcharging was obtained and presented with respect to both the polyelectrolyte and nanoparticle as the central element. Finally, the charge mobility influence along the polyelectrolyte backbone was investigated by considering annealed and quenched polyelectrolyte chains.

Rodlike Complexes of a Polyelectrolyte (Hyaluronan) and a Protein (Lysozyme) Observed by SANS

“…These main trends have been checked experimentally by Kayitmazer et al who compare the binding of chitosan and PDADMAC, two polyelectrolytes with equal charge density but different persistence lengths, to oppositely charges micelles, dendrimers and proteins 32 . However the authors point out that the relevant parameter for binding is not necessarily the intrinsic persistence length of the chain L p , but the flexibility of the chain on the colloid length scale 6 6 In parallel, computer simulations also studied the role of electrostatic interactions in mixtures of charged strings with charged spheres and their interplay with parameters such as chain stiffness, at first in simulations involving only one protein and one polyelectrolyte chain 30,31 , and more recently on systems dealing with several proteins in the presence of an oppositely charged polyelectrolyte 33, 34 . In ref [34], the heterogeneous charge density of proteins in the presence of weak polyelectrolyte has also been taken into account, whereby different chain lengths and ionic strengths were employed:…”

The numerical study of the adsorption of flexible polyelectrolytes with the annealed charge distribution onto an oppositely charged sphere by the self-consistent field theory

“…There is an increasing amount of computational research investigations of the adsorption of proteins on charged surfaces. [26][27][28][29][30][31][32][33][34][35][36][37] The computational methods used in the studies include molecular dynamics (MD), Monte Carlo simulation (MC), and Brownian dynamics (BD). The effects of solution properties such as the pH and the ionic strength, and protein properties such as the shape, the size, the sequence of the amino acids, the charge sites, and the hydrophobicity, as well as the surface characteristics on the adsorption and conformational behaviors of proteins were examined in these molecular simulations.…”

Formation of Complexes between Nanoparticles and Weak Polyampholyte Chains. Monte Carlo Simulations

“…43,44 Several competing effects were pointed out such as the attractive interaction between the charged PE monomers and the NP or the increase of the electrostatic repulsions along the PE chain with the increase of the pH of the solution. Primary structure and stiffness of a weak PA chain were also concomitantly investigated.…”