Confined carrier and regulatory mechanism of single-atom catalysts for biomedical applications

<p indent="0mm">Since the concept of “single-atom catalysis” was proposed by Chinese scientists in 2011, single-atom catalysts have attracted great potential for applications in fields such as energy, environment, and biomedicine. Compared to traditional nanoparticle or nanocluster catalysts, single-atom catalysts have advantages such as maximizing atomic utilization, unique electronic structures, and enhanced catalytic activity/selectivity. Especially in the field of biomedicine, metal-based single-atom catalysts have a significant advantage in their high stability in complex physiological environments since they do not produce biological toxicity caused by the aggregation of a large number of metal ions. This review summarized the latest research progress on the types of confinement carriers, performance regulation mechanisms, and applications of single-atom catalysts in the field of biomedicine in recent years. Firstly, the single-atom active sites-loaded carrier is an important component of single-atom catalysts, which has a remarkable influence on the performance of catalysts. In response to the demand for smaller particle size and good biocompatibility of catalyst carriers in the field of biomedicine, this review focused on the research progress of different types of carrier materials such as metal and compound carriers, carbon-based carriers mainly composed of metal organic frameworks, and silica-based carriers for the confined loading of single-atom active sites. Subsequently, based on the relationship between atomic valence states, coordination structures, and performance regulation mechanisms, the biological performance regulation mechanism of bio-applicable single-atom catalysts was discussed in detail. The majority of single-atom active sites are located in the metal single-atom sites of the catalytic center, and the structure of the active center greatly affects its ability to adsorb substrates and intermediate products, as well as the energy required for bonding and cleavage during the catalytic process. Next, we summarized the research progress of single-atom catalysts in different disease models (such as infected wounds, tumors, arthritis diseases, etc.) as well as in fields such as bioimaging and biosensing. Due to their unique atomic-level structure, efficient catalytic properties, and good biosafety, single-atom catalysts provide new possibilities for developing novel and efficient bio-applicable single-atom catalysts with high selectivity and good biocompatibility. Finally, we looked forward to the development and challenges of bio-applicable single-atom catalysts. Currently, there are still some issues such as high preparation costs, further verification of long-term biosafety, mechanisms for enhancing/deactivating catalytic activity in physiological environments, and a certain gap between catalytic activity and natural enzymes. This review aims to deepen people’s understanding of the regulatory mechanisms and biological effects of single-atom catalysts and promote the development of single-atom nanomedicine.