Atomically Precise Metal Nanoclusters for Bioimaging and Therapy: Progress and Perspectives.

Nanomaterials that simultaneously possess bioimaging and therapeutic functions along with excellent biocompatibility have long been pursued for early disease detection as well as precise therapy, which is critical for enhancing the cure rates and quality of life for patients. The recent advent of atomically precise metal nanoclusters (MNCs) is expected to contribute to the realization of this goal. MNCs are of ultrasmall size (<3 nm) and truly monodisperse, comprising a specific number of atoms in the range of several to hundreds of metal atoms, which endows them with efficient renal clearance, thereby ensuring their excellent biocompatibility. Furthermore, MNCs with discrete electronic energy levels can be tailored to exhibit superior photoluminescence in the near-infrared region (e.g., 1000-1700 nm), and MNCs are also characterized by exceptional photostability and large Stokes shifts. All these features make them excellent candidates as bioimaging probes with high detection sensitivity, deep tissue penetration, and high spatiotemporal resolution. Moreover, due to the wide-range optical absorption and enzyme-like catalytic activity, MNCs also provide various effective therapeutic strategies, including photothermal therapy, photodynamic therapy, chemodynamic therapy, and radiotherapy. Importantly, with the ligand-engineering and alloying strategies, MNCs can be used in imaging-guided precise therapy. In this Perspective, we first introduce the biologically related properties of MNCs, then present the applications of MNCs in bioimaging and therapy, and finally discuss some existing challenges and future prospects. We hope that this Perspective will stimulate broader interest to multidisciplinary researchers, and the collective efforts will boost the applications of atomically precise MNCs in biomedicine.