Novel quinoline-based chemosensor as specific fluorescence sensing of copper ions in cancer cells and for organelle-specific imaging application

Abstract

This work reports a simple synthesis of a quinoline-based organic molecule, (E)-N′-((6-methoxy-2-oxo-1,2-dihydroquinolin-3-yl)methylene) picolinohydrazide (PHMQ), and its ability to distinguish Cu²⁺ ion. Through the use of spectroscopic and photometric titration techniques, PHMQ’s selectivity toward various cations and anions was examined. In just two minutes, PHMQ showed fast detection of Cu²⁺ ions, and clear spectral fluctuations proposed persistent PHMQ-Cu²⁺ complex formation. The calculated emission quenching constant (1.46 × 10⁵ L/mol) and binding constant (1.25 × 10⁴ L/mol) values suggested that strong emission quenching occurs between the PHMQ and Cu²⁺ ions. A linear reduction in fluorescence response was noted for Cu²⁺ ions concentrations between 2–26 μM, with a detection limit of 43.4 nM. Job’s plot, ESI-mass, NMR titration experiments, and density functional theory (DFT) simulations established a 1:1 stoichiometry for the PHMQ-Cu2⁺ complex. Additionally, PHMQ was efficaciously utilized to quantify Cu²⁺ ions in drinking and tap water samples and HeLa cells, illustrating durable cellular penetrability and a fluorescence ’Turn-Off’ response to Cu²⁺ ions. This sensor also established usefulness in mitochondrial-targeted imaging. For the detection of Cu²⁺ ions in biological and environmental environments, PHMQ is a promising detector due to its high sensitivity, selectivity, and quick response.