A novel fluorescent probe with large Stokes shift for two-photon imaging of biothiols in living cells, liver tissues and tumor tissues

•The probe could determinate Cys in PBS buffer solution within 5 min.•Stokes shift of the probe reached 130 nm.•The probe has been applied for thiols in tissue imaging by two-photon excitation.

Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), the small molecule biological thiols, play essential roles in maintaining human biological systems. Research of quantitative determination of biothiols is always significant. We have designed and synthesized a fluorescent probe ANBI based on a naphthalene-benzo[g]indol-1-ium scaffold, quick respond to biothiols in water. The probe exhibits high stability, high selectivity, good water solubility and biocompatibility. Upon addition of biothiols, notably, probe ANBI showed an intense fluorescence within 5 min and displayed a large Stokes shift of 130 nm (Ex = 460 nm, Em = 590 nm). From the linear relationship of absorbance and intensity vs concentrations of Cys, it was determined that the limits of detection are 2.3 μM and 0.35 μM. Therefore, ANBI can qualitatively and quantitatively detect Cys by spectrometry in biological samples. Successfully, probe ANBI has been applied for biothiols in living HeLa cells by one- and two-photon excitation. Furthermore, we obtain the two-photon excited fluorescence images of ANBI in liver tissues and tumor tissues.

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