CEST chemical exchange saturation

In this chapter, we deal with Gd " " complexes applied as Ti agents in MRI. In the first part of the chapter, we discuss the different relaxation mechanisms and how supramolecular approaches can be used to optimize the efficacy of Gd " "-based contrast agents. Nontoxicity is of prime importance for in vivo nse of metal chelates therefore, we also shortly assess some aspects related to their thermodynamic stability and kinetic inertness. We include a short infioduction to CEST (chemical exchange saturation transfer) agents, a new class of lanthanide-based MRI probes, and discnss how supramolecular systems, particularly liposomes, can be beneficial to decrease the sensitivity limit of CEST detection. In the second part of the chapter. 

CHEMICAL EXCHANGE SATURATION (CEST) CONTRAST AGENTS 874... 

Beside classical MRI, based on the measurement of water abundance in tissues and variation of its relaxation rates, other techniques such as chemical exchange saturation transfer (CEST) and its improved form using paramagnetic compounds (PARACEST) are currently investigated to improve the potential of MRI diagnosis. 

CEST chemical exchange-dependent saturation transfer... 

Chemical exchange saturation transfer (CEST) agents... 

Boronic acids have been used in the development of surface plasmon resonance (SPR) [174,175] quartz crystal microbalance (QCM) sensors [174,176,177], Faradaic impedance spectroscopy [177], ion-sensitive field effect transistors (ISFET) [178], and chemical exchange saturation transfer (CEST) contrast agents in magnetic resonance imaging (MRl) [179]. The swelling of phenylboronic add polymers has also been used to control the release of insulin (180,181]. 

Aime S, Barge A, Belli Castelli D et al. Paramagnetic lanthanide(III) complexes as pH-sensitive chemical exchange saturation transfer (CEST) contrast agents for MRI apphcations. Magn Reson Med 2002 47 639-648. 

Ward, K.M., Aletras, A.H., and Balaban, R.S. (2000) A new class of contrast agents for MRl based on proton chemical exchange dependent saturation transfer (CEST). Journal of Magnetic Resonance, 143, 79—87. 

The CEST effect" " is observed for compounds containing protons in slow chemical exchange with bulk water (medium). On selective saturation of the NMR signal of these slowly exchanging protons, the chemical exchange also transfers the saturation to the bulk water protons resulting in a decreased intensity of their proton signal. Slowly... 

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