Synthesis And Metal Ion MRI Sensitivity Of Quinoline Modified DTPA-Gadolinium Complexes

Magnetic resonance imaging （MRI） is a creativity imaging technology, which play akey role in clinical diagnosis. Contrast agent is an important part of MRI. A new trend ofcontrast agents research is bio-active and bio-responsive MRI contrast agents, one of themis metal-sensitive contrast agents. On the basis of reported works, we designed andsynthesized two kinds of quinoline modified DTPA-Gadolinium complexes asmetal-sensitive contrast agents, and their sensitivity to metal ions was also investigated byrelaxivity analysis.The synthesis route of these two kinds of new contrast agents as follows: Firstly, thetetra-tert-butyl4-propynyl diethylene triamine tetraacetic acid （intermediate6） wasobtained through multiple reactions which start from diethylene triamine. Secondly, twokinds of azide alkoxy quinoline （3a,3b） were synthesized after four kinds of routes trying. Thirdly,6and3a or3b were connected together through click reactionrespectively, then deprotection followed with coordination, two new contrast agents （8a,8b） were obtained finally.After the synthesis finished, the proton longitudinal and transversal time of these twokinds of gadolinium complexes aqueous solutions and same Gd-complexe concentrationsolutions containing equal amount of metal ion (Zn²⁺, Ca²⁺, Mg²⁺or Cu²⁺) were measuredrespectively, following the analysis of relaxivity, hence their sensibility to these metal ionscan obtained. The results showed that8a have an obvious response to Cu²⁺, while have aweak response to other metal ions (Zn²⁺, Ca²⁺or Mg²⁺).8b showed a higher response toCu²⁺, and also some response to Zn²⁺. Therefore8a and8b all can be used as Cu²⁺sensitive contrast agent, and8b can also be used as a Cu²⁺and Zn²⁺bi-metal sensitivecontrast agent, especially in the absence of Zn²⁺.