Dansyl-appended Cu-II-complex-based nitroxyl (HNO) sensing with living cell imaging application and DFT studies

摘要

We introduce herein, a novel copper complex-based fluorescent probe [Cu-II(DQ(468))Cl](+) that exhibits a significant fluorescence turn-on response towards nitroxyl (HNO) with high selectivity over other biological reactive oxygen, nitrogen and sulfur species, including nitric oxide (NO). A smart strategy, involving HNO-induced reduction of paramagnetic [Cu-II(DQ(468))Cl](+) to diamagnetic [CuI(DQ(468))](+) with concomitant fluorescence enhancement via a PET mechanism is focused here. This reduction-based strategy was also supported by X-band EPR response and mass spectroscopy. The metal free probe (DQ(468)) showed high affinity towards Cu2+ to form [Cu-II(DQ(468))Cl](+) with a 0.091 mu M detection limit, which subsequently enabled the detection of HNO in an organo-aqueous medium at biological pH (7.4) in the green wavelength region (lambda(em) = 543 nm) with a LOD of 0.41 mu M. The ground-state geometries of DQ(468), [Cu-II(DQ(468))Cl](+) and [CuI(DQ(468))](+) were optimized by DFT calculations, which revealed that the central metal ion in [Cu-II(DQ(468))Cl](+) is in a distorted tetrahedral geometry with the C1 point group. Additionally, the negligible cytotoxicity and good biocompatibility make the developed probe useful for the in vitro detection of HNO.