Dual-Functional Gadolinium-Based Copper(II) Probe for Selective Magnetic Resonance Imaging and Fluorescence Sensing

A unique gadolinium complex, Nap-DO3A-Gd, comprising a naphthylamine luminescent moiety, a di-2-picolylamine (DPA) binding chelator, and a 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) moiety has been designed and synthesized as a dual-functional probe for selective magnetic resonance imaging and fluorescent sensing of copper(II) in living cells. Nap-DO3A-Gd exhibited a turn-on manner of relaxivity changes and a fluorescent quenching toward Cu2+. Through the introduction of naphthalamide into the Gd3+ contrast agent platform to restrict the coordination ability of the DPA chelator and with Gd3+ coordinating to the DPA moiety to turn away the interferences of other metal cations from Cu2+ detection, the probe featured selective relaxivity changes toward Cu2+ over other metal ions and brought unique Cu2+-specific luminescent responses. The probe was water-soluble with the luminescent detection limit established at 6 ppb and was successfully used for luminescence imaging detection of copper(II) in living cells. The results demonstrated the efficiency and advantage of our approach in the development of a dual-modality image.