Photocalibrated NO release from the zinc ion fluorescent probe based on naphthalimide and its application in living cells

A highly sensitive zinc ion fluorescent probe NOD-NY with controlled release of nitric oxide was designed, synthesized and used for tracking intracellular zinc ions in living A549 cells. NOD-NY was prepared from naphthalimide as the fluorophore and N,N-bis(2-pyridylmethyl)amine as the zinc ion recognition receptor, the amide N atom of the naphthalimide was connected to n-butylamine. Under the irradiation of ultraviolet light, NOD-NY can quantitatively release nitric oxide and generate a highly sensitive zinc ion probe Zn-HN, accompanied by a red-shift process of maximum ultraviolet absorption from 350 nm to 450 nm. Upon addition of Zn²⁺ to the solutions of Zn-HN, a remarkable fluorescence enhancement was observed, which could be attributed to the photo-induced electron transfer (PET) mechanism. By replaced the n-butylamine on NOD-NY with diethylene glycolamine or triphenylphosphine structures, NOD-AY with good biocompatibility and NOD-BY that can target mitochondria were obtained respectively. In addition, the nitric oxide released by NOD-NY enriched in lysosome can diffuse into mitochondria. The released nitric oxide can stimulate metallothionein to release zinc ions, and the light-induced in situ generated zinc ion probe Zn-HN can have a highly sensitive fluorescence response to free zinc ions in living A549 cells.