Metal Nanoclusters as Biomaterials for Bioapplications: Atomic Precision as the Next Goal

Noble metal nanoclusters (NCs) have emerged as a new class of nanomaterials which have great potential in bioapplications. Due to their ultrasmall size and versatile surface chemistry, they show excellent luminescence, high photostability, good biocompatibility, low toxicity, and a high renal clearance rate. In recent years, much work has been reported toward the bioapplications of metal NCs, especially the Au, Ag, and Cu NCs. In this Review, we first discuss the crucial factors of metal NCs for their use as biomaterials, including the size, surface chemistry, photoluminescent properties, cytotoxicity, and metabolic activity. Then, we highlight some recent advances of metal NCs in bioapplications, such as biosensing, bioimaging, biomedical diagnosis, and therapy. It is noteworthy that the metal NCs perform quite well in cancer treatment. Finally, we have briefly discussed the current challenges and our perspectives on metal NCs in bioapplication research and further transformation into clinical application.