A novel benzothiazole-based fluorescent probe for continuous detection of Cu2+/S2− and its application in cell imaging

In this paper, a fluorescent probe methyl(E)-2-(3-(benzo[d]thiazol-2-yl)-2-hydroxy -5-methylbenzylidene) hydrazine-1-carboxylate (DYH) based on benzothiazole was designed and synthesized. The characterization involved NMR, HRMS, and crystal structure analysis. In case of the existence of other competing cations, the probe DYH showed high-affinity for Cu2+, and the resultant DYH-Cu2+ showed exceptional capacity to recognize S2− in CH3CN/HEPES (7/3, v/v, HEPES 0.1 M, pH = 7.3). The detection limits of DYH for Cu2+ and DYH-Cu2+ for S2− were 0.56 μM and 0.67 μM, respectively. It was determined that the binding stoichiometry between the DYH and Cu2+, as well as DYH-Cu2+ and S2−, was 1:1 according to the job's curve. The pH of the probe and complex was stable between 4-10. Colorimetric experiments of the probe DYH were conducted using test paper as a carrier. Additionally, DYH was used for fluorescence imaging of Cu2+ and S2− in Hela cells with poor cellular toxicity and good cell permeability.