Cationic carbon dots: A novel class of mimetic enzymes

Natural enzymes are highly efficient catalysts with strong substrate specificity, making them ideal for biomedical applications. However, they often face issues such as variability, high costs, challenging preparation processes, and difficulties in large-scale production. This has led to significant efforts in developing effective nanoenzymes and exploring their application potential. In recent years, carbon dots (CDs) have gained attention due to their strong fluorescence, excellent biocompatibility, and low cytotoxicity. Cationic CDs, which possess a positively charged surface, have shown the ability to mimic natural enzyme applications. The positive charge on the surfaces of these nanomaterials significantly influences their fluorescence, biological activity, and interactions with other biomolecules. Therefore, understanding how surface charge affects the performance of CDs is crucial for enhancing their usability. Considerable progress has been made in the design, synthesis, and mechanistic research of enzyme-like cationic CDs, as well as their advanced applications. This article reviews the latest research on the design structure, catalytic mechanisms, biosensing capabilities, and biomedical applications of enzyme-like cationic CDs. First, we review the synthesis strategies for cationic CDs and how surface charge influences their physical and chemical properties. Next, we highlight various applications of these cationic CDs, demonstrating their use in areas such as detection, biomedical applications (including antibacterial agents, gene carriers, and therapeutic agents), catalysis, and more. Finally, we discuss the challenges and obstacles faced in the development of cationic CDs and look forward to exploring new applications in the future.