Tailoring gold nanocluster properties for biomedical applications: From sensing to bioimaging and theranostics

Gold nanomaterials have emerged as versatile systems which hold a great promise for several biomedical applications. Among them, gold nanoclusters (AuNCs) — ultra-small nanoparticles— have gained attention due to their unique optical and electronic properties arising from their small size, quantum confinement effects, and surface ligands. Their biocompatibility, efficient renal clearance, photoluminescence (PL), and catalytic activity make them great candidates for practical biomedical applications, such as bioimaging and therapy. In this review, we devote our attention to the burgeoning research in this area focusing on three main and highly intertwined topics. First, we present the different methods for AuNC synthesis alongside the key properties of AuNCs (magnetism, catalytic activity, and PL). This is followed by a description on how to fine-tune PL as their key optical property. Lastly, the potential applications of AuNCs are discussed in detail, with a particular focus on sensing, bioimaging, and on nanomedicine.