A turn-on fluorescent lysine nanoprobe based on the use of the Alizarin Red aluminum(III) complex conjugated to graphene oxide, and its application to cellular imaging of lysine

The authors describe a rationally designed nanoprobe for the fluorometric determination of lysine. It is based on a ternary complex consisting of graphene oxide, aluminum ions (acting as a bridging agent), and alizarin red (GO-Al-AR). The fluorescence of the complex (with excitation/emission maxima at 440/512 nm) is weak but significantly enhanced upon the addition of lysine, probably due to a photoinduced electron transfer signalling mechanism. The method has a detection limit of 2 mg L−1 of lysine and a linear range from 25 mg L−1 to 250 mg L−1. It was applied to image lysine in human retinal pigment epithelium cells.