Single Atom-Engineered NIR-II Gold Clusters with Ultrahigh Brightness and Stability for Acute Kidney Injury.

Near-infrared-II (NIR-II) imaging has shown great potential for monitoring the pathological progression and deep tissue imaging but is limited to present unmet NIR-II agent. Present fluorophores show a promising prospect for NIR-II imaging, but brightness and photostability are still highly challenging during real-time monitoring. In this work, atom-engineered NIR-II Au24 Cd1  clusters with ultrahigh brightness, stability, and photostability are developed via single atomic Cd doping. Single atom Cd substitutions contribute to Cd 4d state in HOMO and redistribution of energy level near the gap, exhibiting 56-fold fluorescence enhancement of Au24 Cd1  clusters. Meanwhile, single atomic Cd reinforces CdAu bond energy, formation energy, and stabilized cluster structure, leading to persistent stability for up to 1 month without decay, as well as excellent photostability of 1 h without photobleaching, much longer than clinically approved indocyanine green (<5 min). In vivo imaging shows gold clusters can monitor acute kidney injury (AKI) even after 72 h of injury, enabling evaluating progression at a very long window. Meanwhile, the bioactive gold clusters can alleviate AKI-induced oxidative stress damage and acute neuroinflammation. Single atom-engineered gold clusters exhibit molecular tracking and diagnostic prospect in kidney-related diseases.