Ultra‐Stable Gold Nanoparticles with Tunable Surface Characteristics

Abstract Gold nanoparticles (Au NPs), as a class of functional nanomaterials, have attracted considerable interest for biomedical applications owing to their unique chemical and physical properties. However, colloidal solutions of Au NPs are thermodynamically unstable because of their high surface energy, resulting in poor stability and biocompatibility in physiological environments. Herein, we present a novel strategy for coating Au NPs using in situ polymerization to form a three‐dimensional (3D) network polymer shell around each particle. This approach enables the creation of an ultra‐stable core‐shell structure that effectively improves biocompatibility and stability, even in complex biological environments. The surface characteristics of the polymer shell can also be precisely tailored by carefully selecting the monomers to meet biomedical application requirements. These properties enable prolonged circulation within the bloodstream and enhanced tumor targeting in mice. This strategy offers an ultra‐stable, aqueous‐based, and biocompatible polymer shell for Au NPs, paving the way for the surface modification of gold nanomaterials in biomedical applications.