Single-atom nanozymes: A rising star for biosensing and biomedicine

Nanozymes with excellent and intrinsic enzyme-mimicking characteristics have been considered as extremely promising alternatives to natural enzymes due to their merits of low cost, easy storage, tunable catalytic activities, high stability, and easy large-scale production. Enormous efforts have been devoted to the development of highly efficient nanozymes and the promising applications of nanozymes. Recently, single-atom nanozymes (SAzymes) emerge as a novel high performance nanozyme and have attracted extensive study interests. Moreover, SAzymes with homogeneously dispersed active sites and well-defined coordination structures offer rare opportunities to explore their structure–activity relationship and regulate the geometric and electronic properties of catalytic active sites. By now, SAzymes have made impressive progresses in their design synthesis, mechanism study, and advanced applications. In this review, we comprehensively summarize the latest research advances on the design construction, catalytic mechanism, biosensing and biomedicine applications of SAzymes. First of all, the synthesis strategies (including wet-chemical synthesis, metal organic frameworks (MOFs)-derived strategy, and atom trapping strategy, etc.), active centers, and catalytic mechanism of SAzymes are considerately summarized. Then, the attentions are concentrated on their advanced applications, including biosensing and biomedicine applications (i.e., cancer therapy, antibacterial, cytoprotection, wound healing, and sepsis treatment). At the end of the article, the challenges and opportunities on the further studies of SAzymes (including design, synthesis, and surface modification, selectivity, catalytic activity, diversities, catalytic mechanism, and promising applications) are tentatively proposed.