Curcumin-Based Fluorescent and Colorimetric Probe for Detecting Cysteine in Living Cells and Zebrafish

We synthesized a new curcumin-based fluorescent and colorimetric probe (CAC) and described its application for the specific detection of cysteine (Cys), including in solution, in living cells, and in a living vertebrate organism. The probe CAC itself showed a strong fluorescence emission, the conjugate addition–cyclization reaction with Cys resulted in the fluorescence quenching at 490 nm and the absorbance decreasing at 400 nm, accompanied by the appearance of a new absorption band at 427 nm. The probe CAC exhibited higher properties such as acting as a "naked eye" probe, readily synthesized, highly selective for Cys, and a lower detection limit of 0.19 μM. In addition, the probe CAC can be successfully applied to detect Cys in living cells and zebrafish with good cell and organism permeability, indicating its significant potential in living biological systems.