Protein-Interference-Free and Kidney-Targeting NIR Fluorophores for Accurate in Vivo Imaging of H2S2 during Kidney Ferroptosis.

High-fidelity kidney function imaging is important for assessing the nephrotoxicity of drugs and diagnosing renal diseases. However, the current challenges in achieving accurate kidney imaging include unspecific signal enhancement due to albumin binding and relatively low distribution of imaging agents in kidneys. Here, for the first time, a side-chain engineering strategy that incorporates hydrophilic six-membered heterocycles into aza-hemicyanine for generating high-performance kidney imaging agents with protein-interference-free and kidney-targeting features is proposed. Based on these unique aza-hemicyanine dyes, the first kidney-targeting and albumin-insensitive H2S2 near-infrared (NIR) fluorescent probe NA-H2S2 is designed, which demonstrates effective kidney distribution following intravenous injection and is specifically activated by H2S2. The designed probe presents a highly rapid, selective and sensitive response to H2S2 with a detection limit as low as 24.21 nm. Additionally, it successfully achieves real-time in vivo NIR fluorescence imaging of H2S2 during erastin/cisplatin induced renal ferroptosis. Moreover, it also enables rapid detection of H2S2 through in vitro optical urinalysis, offering significant diagnostic value for renal ferroptosis. Overall, this study not only presents a practical kidney-targeting H2S2 fluorescent probe NA-H2S2 with increased imaging accuracy but also provides promising kidney-targeting and albumin-insensitive aza-hemicyanine dyes for further development of kidney disease-related probes.