Emerging single-atom nanozymes for catalytic biomedical uses

The past four years have witnessed booming progress in single-atom nanozymes (SANs), one of the newest generations of nanozymes with atomically dispersed metal sites for catalytic biomedical uses. They show distinct advantages over their nanoparticle-based counterparts, such as well-defined electronic/geometric structures and complete atomic utilization efficiency, thus offering opportunities to develop advanced nanozymes for practical uses. The atomically dispersed active centers in SANs could also facilitate the precise regulation of catalytic performance, while probing structure-activity relationship for in-depth understanding of mechanism. In this review, we first introduce the synthetic approaches, surface engineering, and characterization techniques of SANs. Subsequently, we discuss the enzyme-like properties of SANs, including some strategies for boosting their catalytic activities. Furthermore, we present their biomedical applications, ranging from biosensors, antibacterial uses, antioxidants, to therapeutics. Finally, the challenges and opportunities of SANs are prospected.