A reactive probe for Co²⁺ ion detection based on a catalytic decomposition process and its fluorescence imaging in living cells

Abstract

A novel reactive fluorescent probe for cobalt ions was prepared based on integration of thiourea functional groups, coumarin, and naphthalimide fluorophores. There was no fluorescence observed for the probe itself, however, in the presence of cobalt ions, catalytic decomposition occurred for the probe and coumarin molecular fragments were produced that emitted blue fluorescence. This enabled the probe to be used as a ‘turn on’ reagent for detection of cobalt ions. Under physiological pH conditions and in appropriate solvent systems, an obvious fluorescence enhancement for cobalt ions was observed in selective experiments. Competition experiments indicated that cobalt ions could still induce fluorescence enhancement in the presence of other metal ions. Sensitivity experiments showed that the detection limit for cobalt ions was 6.0 nM. Dynamics research demonstrated that the catalytic process was a pseudo‐first‐order reaction and the reaction constant (kobs) was calculated to be 1.49 × 10−2 min−1. In addition, the mechanism of catalytic decomposition could be demonstrated using electrospray ionization mass spectrometry and thin layer chromatography experiments. Cell fluorescence imaging experiments demonstrated that the probe could be used to detect cobalt ions in living HeLa cells.

Small-Molecule Fluorescent Probes for Binding- and Activity-Based Sensing of Redox-Active Biological Metals

“…He and co-workers prepared 330 , which comprises 1,8-napthimide and 4-aminocoumarin fluorophores linked by a thiosemicarbazide . The probe alone has very weak fluorescence, but undergoes a 87-fold increase in intensity at 425 nm corresponding to the emission wavelength for the coumarin.…”

“…He and co-workers prepared 330, which comprises 1,8napthimide and 4-aminocoumarin fluorophores linked by a thiosemicarbazide. 529 The probe alone has very weak fluorescence, but undergoes a 87-fold increase in intensity at 425 nm corresponding to the emission wavelength for the coumarin. Mechanistic studies suggested that Co(II) binding to the thiosemicarbazide results in cleavage of the naphthalimide-N bond, releasing the coumarin thiosemicarbazide, which subsequently decomposes to 4-aminocoumarin.…”

Recent advances in the fluorimetric and colorimetric detection of cobalt ions

“…The main application of probe 36 was the detection of cobalt ions in HeLa cells. 65 Chemosensor 38 based on a coumarin ring was synthesised. An absorption band was observed at 470 nm when this probe was analysed by the ultraviolet-visible spectroscopic technique The pH range of 2.0 to 12.5 was found to be the best working range for probe 38.…”

Highly sensitive benzothiazole-based chemosensors for detection and bioimaging of peroxynitrite in living cells

“…S18 †). And according to the formula Ln[(F max − F t )/ F max ] ¼ −k't, 52,53 their pseudo-rst-order rate constants were determined as 1.49 Â 10 −2 s −1 (Fig. S19a †) and 1.23 Â 10 −2 s −1 (Fig.…”