Transition metal induced switch of fluorescence and absorption response of a Zn(ii)porphyrin–DNA conjugate to cysteine derivatives

Abstract

We report a supramolecular zinc(II)tetraarylporphyrin–oligothymidine/metal ion system (ZnPorT8/M²⁺) for dual optical sensing of cysteine (Cys) and glutathione (GSH) with a tunable spectroscopic outcome. Transition metal ions (M²⁺ = Hg²⁺ or Cu²⁺) allow the switching of the emission and absorption response of the ZnPorT8/M²⁺ complex. The ZnPorT8/Hg²⁺ complex exhibits turn-on fluorescence sensing (fluorescence enhancement), whilst the ZnPorT8/Cu²⁺ system exhibits turn-off sensing (emission quenching) of Cys and GSH. The ZnPorT8/Hg²⁺ and ZnPorT8/Cu²⁺ complexes have an excellent limit of detection (LOD(em)) for Cys (5.95 nM and 11.99 nM, respectively) and GSH (3.34 nM and 13.50 nM, respectively).