Ratiometric fluorescence imaging of endogenous selenocysteine in cancer cell matrix

Monitoring intracellular selenocysteine (Sec) is of significant interest for studying Sec metabolism and disease-relevant changes in Sec homeostasis. Herein, we rationally designed an ICT-based ratiometric probe (Rat-Sec) for selectively discriminating endogenous Sec in a live cell matrix. By utilizing an acrylate moiety, Rat-Sec manifested significantly ratiometric and red-shifted (∼117 nm) fluorescence signals within 1 min, and concomitantly demonstrated apparent color alteration from colorless to faint yellow in the presence of Sec. When applied to quantitatively detect Sec under physiological conditions, Rat-Sec gives a detection limit of 12 nM. Offering great advantages due to its ratiometric nature and high specificity and selectivity, Rat-Sec provides reliable fluorescence quantification and rapid tracking of exogenous and endogenous Sec in living cells.