Development of an oxidative dehydrogenation-based fluorescent probe for Cu2+ and its biological imaging in living cells.

Based on a boron dipyrromethene (BODIPY) derivative containing an N, O and S tridentate ligand, a Cu(2+) fluorescent probe BTCu was developed. The detection mechanism was verified as Cu(2+)-promoted oxidative dehydrogenation of an amine moiety, leading to a formation of a fluorescent Cu(+)-Schiff base complex. Free BTCu exhibited a maximum absorption wavelength at 496 nm, and a very weak maximum emission at 511 nm. Upon addition of various metals ions, it showed large fluorescence enhancement toward Cu(2+) (417-fold in MeCN and 103-fold in MeCN/HEPES solution, respectively) with high selectivity. The detection limits are as low as 1.74×10(-8) M and 4.96×10(-8) M in the two different solutions, respectively. And BTCu could work in a wide pH range with an extraordinary low pK(a) of 1.21±0.06. Using fluorescence microscopy, the probe was shown to be capable of penetrating into living cells and imaging intracellular Cu(2+) changes.