Gram-scale synthesis of neodymium-enriched carbon dots as a CT/NIR-II fluorescence bimodal imaging probe for early diagnosis of acute kidney injury.

Acute kidney injury (AKI) is a highly morbid and lethal syndrome that is often clinically "silent" in early stages. Multimodal imaging, which integrates complementary structural and functional insights from various techniques, holds great potential to enhance diagnostic sensitivity and accuracy. However, developing a single-agent probe that effectively combines multiple imaging modalities for AKI remains a significant challenge. Herein, we show neodymium-enriched carbon dots (Nd-CDs) as a novel bimodal imaging probe for the early diagnosis of AKI by using computed tomography (CT) and the second near-infrared window (NIR-II) fluorescence. Nd-CDs with high metal doping level (17.9%) can be achieved on a gram-scale (2.1 g) through a "bottom-up" strategy. The ultra-small hydrodynamic size (<2 nm) endows Nd-CDs with rapid renal clearance. Benefiting from narrow-band NIR-II fluorescence emission at 1060 nm and strong X-ray attenuation, Nd-CDs provide high-spatial-resolution CT and highly sensitive fluorescence imaging in vivo. In a cisplatin-induced AKI rat model, Nd-CDs-based bimodal imaging reveals a pronounced delay in renal metabolism caused by tubular injury, which precedes abnormalities in blood biochemical parameters, enabling early diagnosis and progression monitoring of AKI. The proposed strategy provides new insights into the development of single-agent probes integrating multiple imaging modalities and opens up a new way for early diagnosis of AKI.