Recent progress in atomically precise metal nanoclusters: From bio-related properties to biological applications

Atomically precise noble metal nanoclusters (e.g. gold and silver nanoclusters), consisting of a few to a hundred atoms, have emerged as promising materials in the field of nanoscience and life science. They have attracted significant interest owing to their discrete energy levels, intriguing molecular-like behaviors, and unique bio-related properties such as controllable optical absorption, adjustable photoluminescence, circularly polarized luminescence and clusterzyme activity, which can be tailored through tuning the size, composition distribution and types of the capping agents. These valuable bio-related properties of noble metal nanoclusters with defined structures have ensured them to become an emerging and promising class of artificial theranostic agents in biological applications, including bioimaging, modern antibacterial agents, drug delivery systems and cancer therapy. This review comprehensively and systematically summarizes recent advances in the bio-application of gold and silver nanoclusters for fluorescent bioimaging, antibacterial agents, drug delivery and cancer therapy, highlighting the key factors or efficient strategies to tailor these bio-related properties. Moreover, the current challenges and the future development directions of noble metal nanoclusters are also discussed. • Comprehensive overview of the bio-related properties of atomically precise metal nanoclusters. • Timely summary of the biological application of atomically precise metal nanoclusters. • Detailed description of key factors and strategies to tailor bio-properties and biological application of metal nanoclusters. • Discussion of the current challenges and future directions for the biological applications of metal nanoclusters.