Sustainable biopolymers are intriguing motifs for transferring the distinct biocompatibility and recognition into inorganic nanoparticles, which have a potential to be used in biomedicine applications. Here we report scalable production of water-soluble chitosan polymers from N-acetylation. One-pot aqueous synthesis of water-dispersible gold nanospheres is developed using the acetylated chitosan as a stabilizer and a reducing agent. The inherent aqueous solubility of the acetylated chitosan renders the gold nanospheres dispersible in water and enables for controlling the uniform size and monodispersity. The acetylated chitosan-stabilized gold nanospheres with plasmonic and biocompatible properties are used as efficient bioprobes for the selective detection of various biochemical agents of melamine, bacteria, and uric acid. (C) 2014 Elsevier B.V. All rights reserved.