A two-photon “turn-on” fluorescent probe for both exogenous and endogenous selenocysteine detection and imaging in living cells and zebrafish

Selenocysteine (Sec) is recognized as the 21st amino acid employing as an essential building block for selenoproteins (SePs), which plays a significant role in various physiological processes. Therefore, there is an urgent need to reasonably develop some reliable and rapid methods for Sec detection in biological systems. In this work, we reported a new two-photon (TP) fluorescent probe BNT-Sec for Sec detection and imaging in living cells and zebrafish with two part: (1) a D-π-A-structured naphthalene derivative as a TP fluorophore; (2) a well-know Sec responsive site with strong intromolecular charge transfer effect (ICT) to selectively detect endogenous and exogenous. In the presence of Sec, probe BNT-Sec can initiate a Se-dependent specific aromatic nucleophilic substitution reaction, which exhibited BNT-Sec had a large fluorescence intensity enhancement with ~18.9-fold at 510 nm, a high sensitivity low LOD value’ 10.6 nM, good light stability, strong specificity, pH stability and low cytotoxicity. In addition, BNT-Sec can be conveniently used to detect Sec in living cells and zebrafish for TP imaging due to the great TP measurement properties of fluorophore, exhibiting it has the potential to reveal the role of selenocysteine in physiological and pathological processes in further biological applications.