A novel viscosity/HClO dual-responsive fluorescent probe with mitochondrial localization ability and bio-imaging

A novel dual-responsive fluorescence probe, 2-[(1E)-2-[(6-dimethylthiocarbamoylnaphthalen)-2-yl]-ethenyl]-3-ethylbenzothiazolium iodide (TNB) has been developed for the discriminative sensing of viscosity and hypochlorous acid (HClO). Under high-viscous conditions, TNB's green fluorescence at 506 nm was switched on due to the inhibition of intramolecular bond rotation. Whereas in PBS aqueous buffer, the release of thiocarbamate moiety from TNB triggered by HClO forms a phenolic compound (NB-OH), which was chlorinated by excessive HClO to the final product (NB-Cl-OH) with near-infrared emission at 676 nm. Consequently, TNB enables the dual-colour visualization of viscosity or HClO fluctuations, showcasing good selectivity and photo-stability, high sensitivity, and quick response to HClO (∼ 4 s). Moreover, the fluorescence of NB-Cl-OH is highly responsive to viscosity changes, achieving dynamic monitoring of HClO and viscosity simultaneously. Possessing mitochondria-targeting capability, TNB realizes the dual-channel imaging of viscosity/HClO alterations in the process of oxidative stress and inflammation in live cells and zebrafish.