A highly stable and water-soluble bis-benzoxazole-based fluorescent dye (BBT-mPEG) is prepared by the treatment of 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol (BBT) with methoxypolyethylene glycol (mPEG-OH, average Mw = 350). BBT-mPEG exhibits a blue emission at λem = 445 nm in water upon excitation with 365 nm light, and a moderate fluorescence quantum yield (![[curly or open phi]](http://www.rsc.org/images/entities/i_char_03d5.gif) f = 0.33, in H2O) is obtained using quinine sulfate (f = 0.557, in H2SO4) as the reference. It is found that BBT-mPEG shows good photo-stability and large Stokes shift (Δλ = 80 nm) in aqueous solution in entire pH range (pH = 1–14). Moreover, it is also found that BBT-mPEG exhibits low cytotoxicity and enhanced fluorescence in cells; using HeLa cells as a prototype, a clear cellular imaging is obtained. Physical Review B, 2014 Confocal laser scanning microscopic images of HeLa cells incubated with BBT-mPEG (1.0 μM) (left). Confocal laser scanning microscopic images of HeLa cells incubated with BBT-mPEG (1.0 μM) (left). |
