Multiparametric MRI for In Vivo Visualization of Renal Inflammation in Acute Kidney Injury

ABSTRACT Renal ischemia‐reperfusion injury (IRI) is a major cause of acute kidney injury (AKI), yet early diagnosis remains challenging owing to the lack of sensitive and specific approaches for in vivo inflammation visualization, which severely limits accurate diagnosis and effective intervention. To address this limitation, this work reports an inflammation‐targeting multiparametric MRI strategy based on a nanoprobe (NPs@PEG‐PEP) for real‐time visualization of AKI‐associated inflammatory responses. NPs@PEG‐PEP was modified with functional peptides targeting CD137, which is an activation‐induced immune receptor serving as an upstream mediator of inflammatory cascades. This approach enables nanoprobes to selectively target and accumulate surrounding inflammatory cells in AKI‐affected kidneys. In addition, constructed from NaGdF 4 nanoparticles, the nanoprobe simultaneously enhances dynamic contrast‐enhanced MRI (DCE‐MRI) and susceptibility‐weighted imaging (SWI) to capture distinct vascular perfusion differences and inflammatory cell infiltration between injured and contralateral kidneys. The inflammatory imaging signal persists for up to 18 h and correlates well with histopathological findings, including H&E staining and CD11b immunofluorescence. Moreover, the biological safety of the nanoprobe is confirmed via cytotoxicity assays, hemolysis tests, and histopathological evaluations. Overall, this work establishes an inflammation‐targeting multiparametric MRI platform that enables spatiotemporal mapping of IRI‐induced AKI progression, offering a promising strategy for early diagnosis and therapeutic monitoring.