A novel TCF-aza-BODIPY-based near-infrared fluorescent probe for highly selective detection of hypochlorous acid in living cells.

Hypochlorous acid/hypochlorite (HOCl/ClO) plays important roles in killing bacterial and causing damage to living tissues, and its abnormal levels could lead to many diseases. Although great efforts have been devoted, fluorescent probes for HOCl/ClO with near-infrared fluorescence, good selectivity/sensitivity, and low background are still important and urgent. In this work, a novel double-bond-linked TCF-aza-BODIPY-based near-infrared fluorescent probe (3) was rationally designed, successfully prepared, and applied for sensing HOCl/ClO in both solutions and living RAW264.7 cells, showing good selectivity and fluorescence "turn-on" phenomenon at 670 nm with low background. The limit of detection towards ClO was determined to be 0.36 μM through the linear fluorescence changes at 670 nm in a broad ClO-concentration range of 0-150 μM. Furthermore, the sensing mechanism was investigated by mass spectrometry and compared with 1, suggesting that the remarkable spectroscopic changes could be ascribed to the oxidization of the double bond to the aldehyde group, accompanied with the leaving of the TCF group. Confocal imaging experiments also confirmed the remarkable intracellular fluorescence enhancements through incubation of ClO and phorbol ester 12-myristate 13-acetate (PMA) in RAW264.7 cells. Therefore, for the first time, we reported a near-infrared TCF-aza-BODIPY-based fluorescent probe for highly sensitive and fluorescence "turn-on" detection of both exogenous and endogenous HOCl in living RAW264.7 cells through the quick oxidation of a conjugated double bond.