An ultrasensitive and selective fluorescent nanosensor based on porphyrinic metal-organic framework nanoparticles for Cu²⁺ detection

Detecting trace amounts of copper ions (Cu²⁺) is of high importance since copper is an essential element in the environment and the human body. Despite the recent advances in Cu²⁺ detection, the current approaches still suffer from insensitivity and lack of in situ detection in living cells. In the present work, a fluorescent nanosensor based on porphyrinic metal-organic framework nanoparticles (MOF-525 NPs) is proposed for sensitive and selective monitoring of Cu²⁺ in aqueous solution and living cells. The MOF-525 NPs with attractive properties, including ultrasmall size, good water dispersity and intense red fluorescence, are prepared via a facile and environment-friendly hydrothermal route. The fluorescence signal of MOF-525 NPs could be quenched statically by Cu²⁺ with high selectivity due to the strong affinity of Cu²⁺ to the porphyrin ligand in MOF-525. The proposed fluorescent nanosensor has a linear response in the range of 1.0-250 nM with a low detection limit of 220 pM. Furthermore, it is successfully employed for the detection of Cu²⁺ in water samples and the intracellular imaging of Cu²⁺ in living cells, demonstrating its great potential in the sensing and biological fields.