A Large-Stokes-shift Iridium(III) Complex-based Hypochlorous Acid Probe for In vivo Imaging of Inflammatory Arthritis

doi:10.1007/s40242-026-5304-0

Abstract

Abstract: Elevated hypochlorous acid (HOCl) levels are closely associated with the onset and progression of inflammatory joint diseases, highlighting the need for imaging probes capable of rapid and accurate HOCl detection in complex biological environments. However, most small-molecule organic fluorescent probes suffer from small Stokes shifts (<100 nm) and severe spectral overlap with excitation light and tissue autofluorescence, which limits their performance in vivo. Here we report an Ir(III) complex-based luminescent probe, Ir-COOH, featuring a large Stokes shift. In aqueous media, Ir-COOH shows an absorption maximum at ca. 540 nm and an emission maximum at ca. 710 nm, corresponding to a Stokes shift of ca. 170 nm, thereby minimizing self-absorption and background interference. Ir-COOH responds to HOCl with fast signal turn-off, high sensitivity (limit of detection: 148.61 nmol/L), excellent selectivity over other reactive species, and good stability across physiologically relevant pH values. Cell experiments indicate low cytotoxicity, and HOCl can be visualized in paraformaldehyde-fixed ATDC5 via luminescence quenching. Moreover, Ir-COOH enables in vivo imaging of endogenous HOCl in a λ-carrageenan-induced mouse arthritis model, providing a sensitive tool for studying HOCl-associated inflammatory arthritis.

Key words: Luminescent probe, Iridium(III) complex, Hypochlorous acid, Bioimaging

HU Xinru, LIU Wanxin, WANG Xiaoqiang, PENG Shuxin, JI Bolin, WEI Peng, GUO Zhijun. A Large-Stokes-shift Iridium(III) Complex-based Hypochlorous Acid Probe for In vivo Imaging of Inflammatory Arthritis[J]. Chemical Research in Chinese Universities, 2026, 42(2): 463-469.

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