A novel fluorescent probe with large Stokes shift for accurate detection of HOCl in mitochondria and its imaging application

Highlights: • The Mito-QL exhibited large Stokes shift (203 nm) and low detection limit (2.4 nM) for HOCl. • The Mito-QL could first target the mitochondria then accurately detect HOCl in mitochondria. • The Mito-QL was utilized to visualize the exogenous/endogenous HOCl in different cells, and the generation of HOCl during the ferroptosis of cells. Hypochlorous acid (HOCl), mainly generated in mitochondria, plays a critical role in various physiological processes. To better understand the role and function of HOCl in mitochondria, herein, we present the design and synthesis of a Mito-QL reporter for probing the HOCl within mitochondria without other interference generated in living cells. Through the combination of TICT/ICT mechanisms, probe Mito-QL, with large stokes shift (203 nm) and low background fluorescence, exhibited excellent sensitivity (900-fold fluorescence enhancement) and selectivity towards HOCl (LOD = 2.4 nM). The co-location experiments confirmed that probe Mito-QL can firstly localize in the mitochondria and then react with HOCl in mitochondria. Also, the probe is capable of imaging endogenous and exogenous HOCl even the generation of HOCl during the ferroptosis of cells, which is beneficial for more efficient application in biological imaging.