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Abstract

Magnetic Resonance Imaging (MRI) is very important tool in clinical diagnostics and biological research, being often superior to other imaging techniques available today as it provides high resolution 3D images of the body and living tissues. The use of contrast agents e. g. Gd(III)-chelates enhances the MR signal and thus improves the quality of obtained images. The development of bioactivated, responsive or smart MR probes is one of the most exciting aspects of current contrast agent research. Their use would enable tracking of numerous biological processes and could potentially provide extremely improtant information in the desease diagnostics and the brain research. Careful design and appropriate synthetic modifications allow for the incorporation of various sensor moieties to DO3A, a widely used percursor for the preparation of these ‘intelligent' probes. Organometallic Gd(III)-chelates thus obtained response to a desired target such as ions or enzymes and alter their magnetic properties changing the relaxation times of the nuclei in surrounding water molecules. For instance, incorporation of the pH sensitive group such as prosphonates on the optimal distance from the lanthanide metal leads to the pH-responsive agent. Similary, coupling of EGTA-, BAPTA- or EDTA-modified Ca(II) chelators results in the Ca(II)-sensitive contrast agents. These agents could potentially be used for the visualization of the neural processes as the pH or concentration of Ca(II) is changing during the neural activity. The development of such smart MR agents would revolutionize neuroimaging and allow the dynamic imaging of the brain function.