Colloidal stability of polymer coated zwitterionic Au nanoparticles in biological media

[Display omitted] •Colloidal stability in dependence of surface charge.•Zwitterionic versus anionic and cationic.•Influence of salt, pH, and protein adsorption of colloidal properties. Amphiphilic copolymers with various charged side chains have been synthesized and used for the coating of initially hydrophobic gold nanoparticles (Au NPs) to stabilize them in aqueous solution. These amphiphilic copolymers are composed of functionalized methacrylic acid-based monomers that are either hydrophobic or hydrophilic and charged: zwitterionic, positive and negative. Not only was the charge of the monomers varied, but also the ratio of the hydrophobic and hydrophilic moieties within the copolymers in order to investigate the effect of the charge density of the NP surface on its stability. To learn more about the interactions between the coated NPs and their surrounding environment, the physico-chemical properties, e.g. zeta potential, of the NPs' polymeric shell and their influence on the NPs' behavior were studied. The stability of the resulting polymer-coated Au NPs against several aqueous media has been tested to obtain a better understanding about the parameters that influence the dispersion of the NPs. Stability tests were performed at different conditions e.g., at different pH, against different NaCl concentrations, and at different concentrations of bovine serum albumin (BSA), which was used as a protein model. Understanding the surface interactions of nanostructures with the environment, is of importance when it comes to introduction of nanosystems into complex biological structures like the internalization of nanometric structures within cells.