Design and synthesis of a novel magnetic resonance imaging contrast agent for selective sensing of zinc ion

A series of new diethylenetriaminepentaacetic acid (DTPA)-bisamide chelators has been prepared and characterized for application as zinc sensors. We have designed and synthesized (GdL^a)^2-, which contains a DTPA-bisamide moiety. The R₁ relaxivity of (GdL^a)^2- solution decreased monotonically on the addition of Zn²⁺. Moreover, (GdL^a)^2- showed high selectivity for Zn²⁺ against Ca²⁺ and Mg²⁺. We also measured the UV-visible spectra and the coldspray ionization (CSI) MS spectra and concluded that the 1-to-1 Zn²⁺ complex of (GdL^a)^2- is stable at higher concentrations of Zn²⁺. These complexes should provide the basis for creating a superior Zn²⁺-sensitive MRI contrast agent and are excellent candidates for incorporation into sensors designed for selective detection of Zn²⁺ in biological applications.