Fluorescence signaling of Zn2+ levels in synthetic urine by dipicolylamine-armed hydroxynaphthalimide

A novel Zn2+-selective fluorescent sensor based on dipicolylamine-armed hydroxynaphthalimide (DPA-NPI) was developed. DPA-NPI showed selective and sensitive fluorescence turn-on type signaling behavior toward Zn2+ ions. The detection of Zn2+ ions was not affected by the presence of commonly encountered physiologically relevant metal ions. Interference from Hg2+, Cd2+, and Cu2+ ions was observed but not critical, because they are present in trace amounts under physiological conditions. The complex formation was confirmed by 1H NMR and mass measurements. The practical application of the sensor for determining Zn2+ levels in synthetic urine was possible with a detection limit of 2.7 × 10−8 M. The signaling of Zn2+ ions in biological samples using fetal bovine serum was also tested.