Highly selective ratiometric fluorescent probe for Au3+ and its application to bioimaging

The 4-propargylamino-1,8-naphthalimide based fluorescent probe 1 has been explored as a sensor for selective detection of Au3+. 4-Amino-1,8-naphthalimides, that possess typical intramolecular charge transfer (ICT) electronic characteristics, have been widely used as versatile platforms for fluorescent probes. The newly designed probe 1 contains a propargylamine moiety at C-4 of the naphthalimide chromophore that reacts with Au3+ to generate a product that has distinctly different electronic properties from 1. Specifically, the probe undergoes a remarkable change in its absorption spectrum upon addition of Au3+ that is associated with a distinct color change from yellow to light pink. In addition, a blue shift of ca. 56 nm also takes place in the emission spectra of the probe. Consequently, I serves as a reaction-based sensor or so called chemodosimeter for Au3+. Importantly, surfactants enhance the rate of reaction of 1 with Au3+, thus, enhancing its use as a real time sensor. Finally, the results of studies probing its application to bioimaging of Au3+ in live cells show that the probe 1 has a unique ability to sense Au3+ in cells and, in particular, in lipid droplets within cells. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.This study was supported by grants from the National Creative Research Initiative (I.S and J. Y) and WCU (R32-10217) programs (NRF)