An NAG-Activatable Bioluminescent Probe for Sensitive Diagnosis of Acute Kidney Injury In Vivo and in Urine Samples

Acute kidney injury (AKI) is a clinical syndrome characterized by a sudden decline in renal function, affecting over 13 million individuals worldwide annually. A hallmark pathological feature of AKI is renal tubular injury, which leads to an early increase in urinary levels of N-acetyl-β-d-glucosaminidase (NAG). However, the sensitive detection of urinary NAG via a bioluminescent assay remains unexplored. Herein, we report an NAG-activatable bioluminescent probe (N-Luc) for the detection of NAG in vivo and in urine specimens. N-Luc exhibited high sensitivity and specificity for NAG, showing a low limit of detection (LOD) of 0.75 U/L. Furthermore, using this probe, upregulated NAG expression was precisely identified in both cisplatin-induced AKI cell and mouse models, allowing real-time visualization of NAG activity in injured kidneys with a high signal-to-background ratio (609:1). Notably, N-Luc enables the detection of urinary NAG upregulation in cisplatin-induced AKI mice as early as 12 h postinjection. Collectively, this work establishes N-Luc as a promising tool for studying NAG-associated pathologies and advancing urinary diagnostic testing.