Design, synthesis and cell imaging of a new 3-thiolflavone fluorescent probe for biothiols

[Display omitted] •The probe 3-STF is first designed based on 3-thiolflavone.•The probe 3-STF exhibited a specific “turn-on” fluorescence response towards biothiols (Cys, Hcy, and GSH) with a large stokes shift of 140.6 nm.•The detection of biothiols did not suffer from the interference of other amino acids.•The detection mechanism was discussed in detail.•The probe 3-STF can be successfully applied to monitor endogenous and exogenous biothiols in HepG-2 cells. Abnormal levels of intracellular biothiol species, including glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), are closely relevant to a variety of diseases. In this study, we first report the design and synthesis of a 3-thiolflavone-based probe 3-STF with an S–S linkage both as the fluorescence quenching agent and the recognition site. Upon treatment with biothiols, the S–S linkage was cleaved by nucleophilic attack of RS-, and 3-STF exhibited a specific “turn-on” fluorescence response at 543.8 nm upon 390 nm excitation. Meanwhile, 3-STF was proved to be highly sensitive and selective for the detection of biothiols over other nucleophiles such as amino acids and H2S. The sensing mechanism was further verified by 1H NMR and ESI-MS analysis. In addition, 3-STF with low cytotoxicity can be successfully applied to detect endogenous and exogenous biothiols in HepG-2 cells.