Rhodamine-based fluorescent and colorimetric sensor for zinc and its application in bioimaging

A rhodamine derivative ZP1, appended with two 1,2,3-triazole moieties via a diaminopropyl linker, is a chromogenic and fluorogenic sensor for Zn2+. In the presence of Zn2+, a colorless solution of ZP1 becomes pink with a maximum absorption of 555 nm and a large fluorescence enhancement (140-fold) at 579 nm (Phi)=0.12). ZP1 is highly selective with Zn2+, among other metal ions including Cd2+, with a binding constant (K-a) of 7.4 x 10(3) M-1 and a detection limit of 1 mu M (65 ppb). Similar rhodamine derivatives with a shorter linker or with a single triazolyl group cannot function as a Zn2+ chemosensor. ZP1 is membrane-permeable and could react with intracellular Zn2+ in cultured HeLa cells. (C) 2016 Published by Elsevier B.V.