Interfacial engineering of gold nanoclusters for biomedical applications

Ultrasmall gold nanoclusters (Au NCs), with a particle size of similar to 1 nm, have recently emerged as a promising class of nanoparticles, due to their well-defined molecular formulae and structures, unique physicochemical properties (e.g., optical absorption and photoluminescence), facile surface functionalization, and good biocompatibility. To explore the therapeutic potentials of these Au NCs, it is important not only to understand the interface between the NC surface and biological environment, but also to achieve desired biological functionalitiesviarational interfacial engineering. In this review article, we first describe the important biological considerations of Au NCs in their design for biomedical applications. We then aim to demonstrate diverse functionalization strategies of Au NCs to improve their physicochemical and biological properties. In the last section, we provide a detailed discussion on the applications of surface-engineered Au NCs in the fields of bioimaging, radiotherapy, photodynamic therapy, and antibacterial therapy, highlighting the important contributions of interfacial engineering of Au NCs to their biomedical applications.