A highly sensitive fluorescent probe based on the Michael addition mechanism with a large Stokes shift for cellular thiols imaging.

A novel fluorescent probe IPY-MAL for thiols was developed based on imidazo[1,5-α]pyridine derivative, which was decorated with a maleimide group. The probe IPY-MAL showed a rapid response (30 s), high sensitivity and selectivity for thiols with a large Stokes shift (140 nm), which was triggered by the Michael addition reaction of thiols toward the C=C double bond of the maleimide group. Moreover, this probe IPY-MAL could quantitatively detect the concentrations of thiols ranging from 0 to 50 μM, and the detection limit was found to be as low as 28 nM. Cell imaging results indicated that the probe IPY-MAL could detect and visualize thiols in the living cells. Graphical abstract A novel imidazo[1,5-α]pyridine-based fluorescent probe was developed for sensitively monitoring and imaging thiols in living A549 cells with a large Stokes shift.