In situ synthesis of multidentate PEGylated chitosan modified gold nanoparticles with good stability and biocompatibility

To realize desirable functions in the rather complex biological systems, a suitable surface coating is desirable for gold nanoparticles, which plays an important role in their colloidal stability and biocompatibility. In this work, a novel multidentate PEGylated chitosan derivative was synthesized by conjugating PEG and dithiolane lipoic acid (LA) to the chitosan backbone. Under reduction conditions, gold nanoparticles (AuNPs) could be in situ formed by the electrostatic interaction between amino groups of the chitosan derivative and gold chloride ions (AuCl4−), with their surface covalently coated by the multidentate PEGylated chitosan via the disulfide bond from LA. After the surface modification, such AuNPs exhibited remarkable colloidal stabilities under extreme conditions, including high salt conditions and complex biological media containing serum. Moreover, the multidentate PEGylated chitosan also provided AuNPs with good biocompatibility and low cytotoxicity, resistance of protein adsorption and anti-phagocytosis by RAW 264.7 cells. This kind of AuNP was expected to be a promising platform for applications in nanomedicine.