Early Diagnosis of Kidney Injury via Ultrasensitive Detection of Urine-Derived Exosomes Using a Dual-Signal Amplification Strategy

Kidney injury is one of the most serious health problems, including drug-induced acute kidney injury (AKI) and disease-induced chronic kidney disease. Neutrophil gelatinase-associated lipocalin (NGAL) carried by urinary exosomes (uExos) has emerged as a potential biomarker for the diagnosis of kidney injury. However, sensitive detection of urinary exosomal NGAL remains challenging due to its low abundance in urine during the early stages of kidney injury. In this study, we developed a highly sensitive uExos analysis platform by integrating deoxyribonuclease I (DNase I)-mediated biomarker cycling with a metal-enhanced fluorescence (MEF) effect for dual fluorescence signal amplification. This method achieved a remarkably low limit of detection (LOD) of 3.02 × 10³ particles/mL, with a linear range from 5 × 10³ to 2 × 10¹¹ particles/mL. Using this approach, we successfully distinguished urine samples from diabetic nephropathy (DN) patients and healthy donors (HD) by analyzing the level of urinary exosomal NGAL. Moreover, in a rat model of cisplatin-induced AKI, our strategy detected abnormalities as early as 12 h postcisplatin injection─significantly earlier than conventional clinical biomarkers such as serum creatinine (sCr) and blood urea nitrogen (BUN). Additionally, this method demonstrated the potential for accurately evaluating the efficacy of anti-AKI therapeutics. In summary, the dual signal amplification strategy presented in this study facilitates early diagnosis of both chronic and acute kidney injury while offering a powerful tool for dynamically monitoring therapeutic responses in kidney disease.