A selenamorpholine-based redox-responsive fluorescent probe for targeting lysosome and visualizing...

A simple selenamorpholine-based fluorescent probe has been designed and synthesized using a combination of selenamorpholine and a BODIPY fluorophore. BODIPY-Se has a low pK_a value of 4.78 because of the selenamorpholine unit, which is beneficial for the probe to detect the lysosome. BODIPY-Se can turn on partial fluorescence only in lysosomes, due to a PET-inhibited process of protonation of selenamorpholine. In addition, the selenamorpholine unit of BODIPY-Se could selectively react with H₂O₂ through a redox reaction, leading to the alteration of the valence state of selenium from Se(ii) to Se(iv) and an additional PET-inhibited process. When BODIPY-Se tracked H₂O₂ in lysosomes, the two PET-inhibited processes would obviously amplify the fluorescence signal in living cells and in vivo. The probe could also detect the redox cycles between H₂O₂ and GSH continuously. Using confocal fluorescence imaging, the fluorescence localization of lysosomes demonstrated that BODIPY-Se could successfully target lysosomes. The probe could not only detect exogenous/endogenous H₂O₂ in living cells, but could also realize real-time monitoring of H₂O₂ in cancer cells and zebrafish. The results proved that BODIPY-Se is a promising fluorescent probe in biological applications.