Dual-response detection of Ni2+ and Cu2+ ions by a pyrazolopyrimidine-based fluorescent sensor and the application of this sensor in bioimaging

Abstract

Herein, a dual-response fluorescent sensor, L, based on pyrazolopyrimidine was designed and developed for the simultaneous detection of Ni²⁺ and Cu²⁺ ions in the presence of other metal ions; the structural characterization of L was carried out by FTIR spectroscopy, NMR spectroscopy, HRMS and X-ray diffraction analysis. The sensor L effectively displayed fluorescence quenching towards the Ni²⁺ and Cu²⁺ ions with high sensitivity without interference from other metal ions. The results reveal that L binds to Ni²⁺ and Cu²⁺ in a 2 : 1 pattern, which matches well with the result of the Job's plot. The association constants of L with Ni²⁺ and Cu²⁺ were 3.2 × 10⁴ M⁻¹ and 7.57 × 10⁴ M⁻¹, respectively. The detection limits (DLs) are down to 8.9 nM for Ni²⁺ and 8.7 nM for Cu²⁺. The fluorescence imaging of L in T-24 cells was investigated because of the low cytotoxicity of L, indicating that L could be used to detect Ni²⁺ and Cu²⁺ in living cells.