CONICET | Buscador de Institutos y Recursos Humanos

In biomedical applications, advanced materials exhibiting bioactivity, for example bioactive ceramic materials and glasses, are attracting increasing attention. To improve the material functionalities, it is necessary to rationally modify their surface properties. For example, nanocolloids in water solution may undergo the ionization of certain surface groups that can improve stability. Also, surface properties can be modified by the adsorption of polyelectrolytes (PE) chains. In the present work, we have studied the interaction between zwitterionic nanocolloids with strong PE chains. We use the Monte Carlo simulation to evaluate the PE adsorption onto nanocolloid surface as a function of solution pH and salt concentration. The zwitterionic surface was localized on one side of the simulation box; the volume and temperature were constant in the simulation. In the initial configuration, a PE chain could or could not be added to the system; the number of molecules of the surface and PE was fixed along the simulation; and there was an explicit representation of small ions originated from the added salt and from the ionization of the surface and PE. The strong PE was represented by a coarse grained model and the nanocolloid surface was represented as an hexagonal lattice of particles. These particles have a charged state that depends on the solution pH and the electrostatic environment. The preliminary results of this research have shown that anionic polyelectrolyte chains can take a brush or loop conformation, at a pH slightly higher than the isoelectric point of substrate, where there are few positive charges at the surface and the strong repulsion of the polyelectrolyte causes it to extend toward the medium. Oppositely, at a pH well below the isoelectric point, the oxide ceramic is positively charged and strongly interacts with the negatively charged polyelectrolyte, which remains near the surface according to a flat configuration.