A porphyrin platform for ratiometric fluorescence monitoring of Zn2+ ion

Abstract

An innovative ratiometric-type fluorescent chemosensor (SP), which appending a 3-picolyl thiourea pendant to a porphyrin fluorophore, has been synthesized for Zn2+ monitoring in aqueous buffer and in biological samples. SP behaved a Zn2+-selective ratiometric change in emission over a broad pH range with a 1:1 stoichiometry. The peculiar and strong coordination ability between Zn2+ and nitrogen atoms facilitating SP to capture Zn2+ via an axial ligation. Spectrofluorimetric titration, NMR analysis, mass spectrometry, and structure derivation further confirmed the proposed pentacoordinated binding mode between SP and Zn2+. Advantages of the SP probe also include a low detection limit, a small dissociation constant, high selectivity and reversibility. Benefiting from the remarkable analytical performance, low cytotoxicity as well as excellent photostability, ratiometric imaging of exogenous Zn2+ fluctuation in live cells is realized with the as-prepared probe. Moreover, SP is able to visualize the endogenous Zn2+ distribution during the development of zebrafish larval. The present strategy may inspire and stimulate the molecular design of more cation probes involves other particular coordination modes.