Review of supra-carbon dots: from functional modification to biological applications

Carbon dots (CDs) tend to assemble and aggregate into supra-CDs due to surface energy-driven forces, electrostatic interactions, and hydrogen bonding. To better utilize the assembly process, external modulation strategies such as protonation regulation, nanoconfinement, solvent polarity control, and directed hydrogen bonding have been employed to design ordered structures. This review summarizes the assembly structures and functional modifications of supra-carbon dots, focusing on strategies to overcome limitations such as rapid renal clearance, shallow tissue penetration of luminescence, and restricted photothermal/photodynamic efficacy. Recent advances in the biological applications of supra-CDs, including bioimaging, drug loading, photothermal therapy, and photodynamic therapy, are systematically discussed. By integrating nanoscale properties with microscale/macroscale functionalities, supra-CDs demonstrate enhanced performance in diagnostics and therapeutics, offering a promising platform for future biomedical applications.