H(2)O(2)‑Responsive Organic Small-Molecule MRI Probes for Acute Kidney Injury Imaging and Detection.

Magnetic resonance imaging (MRI) has high temporal and spatial resolution without exposing patients to radiation, which shows great potential for acute kidney injury (AKI) detection. Typically, MRI uses gadolinium-based contrast agents to increase local signal intensity by distinguishing tissues or organs that are magnetically similar but histologically distinct, which might induce nephrotoxicity risks. In this work, we explored the potential application of easily available nitroxide-based organic radicals as an intravenously injectable MRI contrast agent. Different from the traditional accumulation-based MRI contrast agents, these organic radicals showed redox-responsive turn-off MRI signals to urinary hydrogen peroxide (H(2)O(2)) with ultrafast renal-clearable ability, which provides a new approach to design reaction-based small molecular organic MRI contrast agents for redox-related diagnostic applications.