Fluorescence sensors based on imidazolium for biogenic amines

Abstract

The aim of this work is to design the system for histidine (HD) and histamine (HM) discriminated detection by using the fluorescence sensors including Histamine Blue (HB), imidazole compound (AN) and imidazolium compound (ANI). Firstly, the synthesis of sensors HB, AN and ANI have been achieved. Our first concept was that the combination of sensors HB and ANI discriminated HD and HM by using FRET process. Unfortunately, sensor ANI consisting of a naphthalimide moiety cannot discriminate HD and HM due to a competitive fluorophore against sensor HB. For the second concept, the binding affinity of Cu2+ ion towards the HBHD and HBHM complexes could discriminate the HD and HM detection by using fluorescence technique. The Cu2+ ion bound selectively with HBHD complex and the fluorescent response of HBHD was quenched in the presence of excess Cu2+ ion. Therefore, we successfully discriminated HD and HM by using the combination of sensor HB and Cu2+ ion. Surprisingly, we enabled to apply the fluorescence responses under different guests to construct the logic gates system. Moreover, we have also studied the selectivity of sensors AN and ANI. The results showed that the fluorescence spectra of sensor AN was deeply quenched in the presence of Cu2+ ion. The complex of sensor AN and Cu2+ ion had the log K value for binding affinity of 5.130 with the stoichiometry 1:1. In case of sensor ANI, the fluorescence quenching of sensor ANI was observed in the presence of F- ion. As the binding studies, the log K value of the complex was 3.05 with the binding mode of 1:1. Limit of detection and limit of quantification of F- determination were 0.18 mM and 0.60 mM, respectively. Finally, sensor ANI gave a promising selectivity for F- determination by colorimetric and fluorimetric naked-eye detection.