Development of a semiacenaphthenofluorescein-based optical and fluorescent sensor for imaging cysteine in cells

•An “off-on” fluorescein-based chemodosimeter probe 1 for the recognition of Cys was designed and developed.•Probe 1 exhibited rapid, highly selective and sensitive for determination Cys over Hcy and GSH.•The recognition mechanism was studied by spectroscopy titrations, mass spectra determination and DFT calculations.•Fluorescence cell imaging demonstrated that probe 1 could detect Cys in HeLa cells.