Development of a novel europium(III) complex-based luminescence probe for time-resolved luminescence imaging of the nitric oxide production in neuron cells

Nitric oxide (NO) is a signaling molecule, and plays an important role in some human neuroses. In this work, a novel europium(III) complex, [4′-(3-methylamino-4-aminophenoxy)-2,2′:6′,2′′-terpyridine-6,6′′-diyl] bis(methylenenitrilo) tetrakis(acetate)-Eu3+ (MATTA-Eu3+), has been designed and synthesized as a luminescent probe for the time-resolved luminescence detection of NO. The complex itself is weakly luminescent, but can specifically react with NO under the aerobic conditions to form its triazole derivative, [4′-(3-methyl-4-benzotriazol-6-yl-oxy)-2,2′:6′,2′′-terpyridine-6,6′′-diyl] bis(methylenenitrilo) tetrakis(acetate)-Eu3+ (MBTTA-Eu3+), accompanied by a remarkable luminescence enhancement with a long luminescence lifetime. The luminescence response of the complex to NO is rapid, highly selective and sensitive, and pH-insensitive in aqueous solutions. These properties enable MATTA-Eu3+ to be used as a turn-on luminescent probe for the selective recognition and sensitive time-resolved luminescence detection of NO in a wider pH range. The probe-loaded PC12 cells were prepared, and used for the time-resolved luminescence imaging detection of the glutamate-induced NO production in the cells. The result demonstrated the practical utility of the probe for imaging the NO production in neuron cells.