Fluorescence “Turn-On” Detection of Bisulfite via Specific CN Bond Cleavage: Reactivity, Structure−Property Relationship, and Bioimaging Applications

It is essential to detect HSO3− for ensuring food safety, preventing environmental pollution, and safeguarding human health. We report a new approach for the fluorescence recognition of HSO3−. The key principle lies in exploiting the specific and irreversible cleavage of the CN bond in the probe’s Schiff base structure by HSO3− to achieve signal transduction. Compared with conventional recognition modes, this probe undergoes a specific structural cleavage upon HSO3− triggering, releasing a strongly fluorescent aromatic amine moiety and thereby yielding a fluorescence “turn-on” response with a high signal-to-noise ratio. By systematically tuning the electronic properties of the molecular termini, the reactivity of the imine bond and the corresponding recognition performance can be effectively modulated. Furthermore, the structure−activity relationship between the molecular electronic structure and the sensing performance has been thoroughly elucidated, providing a theoretical basis for the design of highly selective probes. The platform constructed based on this approach exhibits excellent sensitivity and a low detection limit and enables the visual detection of HSO3− in complex matrices, live-cell imaging, and an acute liver injury model, confirming the reliability and application potential of the probe in real biological and environmental samples. This work not only offers a novel and efficient chemical tool for the effective detection of HSO3− but also provides new insight into the development of fluorescence sensing strategies based on covalent bond cleavage.