Seminar by Prof. Janet Morrow on "Transition Metal MRI Contrast Agents that Respond to Biological Environment"
25 Jan 2018
Seminar Room #350
Seminar by Prof. Janet Morrow on "Transition Metal MRI Contrast Agents that Respond to Biological Environment"
Abstract
The development of chemical probes that switch on or off with changes in biological environment is of interest for applications in molecular imaging. Such probes may report on fundamental molecular pathways related to disease. For example, probes that register extracellular tumor pH or redox status may be important in the characterization of metastatic tumor aggressiveness. Our laboratory is involved in the synthesis of new chemical probes (contrast agents) for magnetic resonance imaging (MRI) based on transition metal ions including Fe(III), Fe(II), Co(II) and Ni(II) coordination complexes. Macrocyclic ligands are used for control of spin state, oxidation state and stability of these complexes. The paramagnetic transition metal ion complexes prepared in our laboratory modulate the proton signal of water in the MRI experiment. High spin Fe(III) complexes enhance the relaxation rates of protons, similar to clinically used Gd(III) complexes whereas high spin Fe(II), Co(II) and Ni(II) complexes produce a large change in the chemical shift of neighboring proton resonances without peak broadening. Divalent metal ion complexes are useful as paraCEST (paramagnetic chemical exchange saturation transfer) contrast agents. Paramagnetic metal complexes attached to polymers or lipids are under development as supramolecular CEST agents. Challenges in the design of contrast agents that are responsive to pH, temperature or redox potential and their applications for in vivo imaging studies will be presented.