‘Turning On’ to Glutathione: A Rhodamine‐Based Fluorescent Chemodosimeter with Nanomolar Sensitivity

A new colorimetric and fluorescence turn‐on chemodosimeter for selective detection of GSH over Cys and Hcy with 34‐fold enhancement in emission intensity is reported. Probe 1 exhibited ultra‐sensitivity toward GSH with 0.125 nM detection limit and successfully displayed GSH detection in MCF‐7 live cells. The mechanism of sensing is established by density functional theoretical calculations. The reported probe 1 links two rhodamine fluorophores via a hexamethylene linker offering flexibility and increased fluorescence quantum yield for GSH recognition. It shows selectivity to GSH over cysteine and homocysteine. This nontoxic, cell permeable probe has been successfully applied for imaging cellular GSH in MCF‐7 live cells with detection limit of 0.125 nM.