Rational design of far-red/NIR BODIPY probes for sensitive biothiol sensing in human serum and bioimaging

Biothiols, including cysteine (Cys), glutathione (GSH), and homocysteine (Hcy), are essential for maintaining the redox balance in cells, support cell signaling, and regulate cell death. Abnormal levels of these molecules are linked to many diseases, therefore, detecting them is very important for medical diagnosis and biomedical research. Herein, we report two highly emissive turn-on BODIPY-based fluorescent probes, BTM1-DBS (λ_em = 630 nm) and BTM2-DBS (λ_em = 705 nm), designed by introducing a 2,4,5-trimethoxybenzene unit into the BODIPY core and incorporating a thiol-reactive 2,4-dinitrobenzenesulfonyl (DBS) group. Both probes exhibit excellent photophysical properties, including high quantum yields, large Stokes shifts (60 and 55 nm), and superior photostability, enabling highly sensitive detection of biothiols (Cys, Hcy, GSH) with low limits of detection (69, 79 and 90 nM for BTM1-DBS and 162, 172 and 188 nM for BTM2-DBS). Their effectiveness was further demonstrated through live-cell imaging and human blood serum analysis, confirming their potential as powerful tools for medical diagnostics and biological research.