A novel fluorescent probe based on isocoumarin for Hg²⁺ and Fe³⁺ ions and its application in live-cell imaging

Synthesis of the 2-amino-4-phenyl-6- (isocoumarin-3-yl) -3-cyanopyridine (APICP) containing both isocoumarin and pyridine ring in its structure was carried out, and this compound was characterized by ATR-FTIR, ¹H NMR, and ¹³C NMR spectral techniques. A fluorescence sensor determining Hg²⁺ and Fe³⁺ ions in DMSO/HEPES buffer solution (9/1 v/v, 5 μM, pH 7.0) was developed using the synthesized compound, and the detection limits of the sensor with exquisite selectivity were calculated as 8.12 nM and 5.51 nM for Hg²⁺ and Fe³⁺ ions, respectively. Jobs plot method was used to determine the stoichiometry of APICP-Hg²⁺/Fe³⁺ complexes as 2:1 and FT-IR and ESI-MS methods confirmed the results. Besides, cell growth inhibitory potentials of the sensor over HepG2 cells and in vivo fluorescent cell imaging experiments were conducted. Findings revealed the relatively low cytotoxic effects of the synthesized sensor (IC₅₀: 0.541 ± 0.039 mM), and it could be utilized as an intracellular imaging agent for the determination of Fe³⁺ and Hg²⁺ ions in biological systems.