1,8-Naphthalimide-based ‘turn-on’ fluorescent sensor for the detection of zinc ion in aqueous media and its applications for bioimaging

A 1,8-naphthalimide derivative (1) was intentionally designed and synthesized as a new turn-on fluorescent probe for the detection of zinc ion with high selectivity over other metal ions at pH 7.4 in aqueous media (CH3CN/HEPES, V/V = 6:4). The reaction mechanism is attributed to the replacement of the protons of the O–H groups by zinc ion at the binding site and production of fluorescence which is blocked in the photo-induced electron transfer (PET) process. Remarkable enhancement of up to 13-fold in fluorescence intensity with a 38 nm red-shift was achieved in the detection of zinc ion. Compound 1 was successfully applied to the fluorescence imaging of zinc ion, with a fluorescence emission color produced in the cell nucleus different from that produced in the cytoplasm, in A549, BEAS-2B, CHO, Hela, and HepG2 cells. Furthermore, cytokinesis-block micronucleus (CBMN) assay was carried out in CHO cells using 1 and zinc ion as the imaging agents, showing that the 1-Zn2+ agent is a nucleic acid selective stain, which could be applied in MN assays in different kinds of cell lines.