Biomedical Applications of Single-atom Catalysts

Single-atom catalysts (SACs), which have 100% atomic utilization and fully exposed atomic metal active sites, show distinct advantages in catalytic activity and selectivity, thus have been widely applied in the fields of chemistry, energy, environment and so on. Since the concept of SACs was proposed, the studies about different monometallic atoms loaded on various supporting materials were reported continuously. As the research of nanozyme has attracted increasing attention, SACs were also explored for their enzyme-like activities. Therefore, SACs attract extensive attention in the biomedical domain in recent years, among that, anchoring monatomic metals on nitrogen-doped carbon materials by pyrolysis were the most widespread studied. The M-N,.-C site formed after pyrolysis is similar to the M-N, site of natural metal enzymes, which endows the materials superior enzyme-like activity. Importantly, compared with natural enzymes and nanozymes, SACS own the advantages of simpler synthesis steps, controllable active center and morphology , adjustable coordination environment, better catalytic activity, lower cost, easier commercial application and more convenience to invest relative catalytic reaction mechanism. It is worth mentioning that, metal atoms with enzyme-like activity (such as Au, Pt, Pd) dispersed on supporting materials (like carbon points, metal oxides, 2D material) can also obtain higher enzyme-like activity than nanoparticles or supporting materials themselves. In short, the excellent enzyme-like activity is mainly due to the maximum exposure of monodisperse metal atoms in the biocatalysis reaction. Meantime, the strong interaction between these metal atoms and the supporting materials makes the whole system more stable to achieve long-term catalysis. This paper reviews the application and research progress of SACs in the fields of tumor therapy, antibacterial, antioxidation and biosensor, and some examples will be introduced in detail, including material preparation method, enzyme-like activity, catalytic mechanism and practical application effect. At the end of the review, we briefly summarize the challenges and opportunities about the future application of SACs, so as to provide strategies for the rational design of SACs with multiple properties.