Complexes of selected late period lanthanide(III) cations with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid amide (DOTAM)-alkyl ligands - a new platform for the development of paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance imaging (MRI) contrast agents

A series of 18 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid amide (DOTAM)-alkyl derived complexes with selected late lanthanide(III) cations (Dy³⁺, Tb³⁺, and Tm³⁺) has been synthesized; their magnetic properties have been evaluated and compared to those derived from DOTAM. Peralkylation of cyclen with corresponding N-iodoacetyl amines was utilized as the key step in the synthesis. Chemical exchange saturation transfer (CEST) spectra of the complexes have been acquired at 37 ^oC, revealing that Tm³⁺-derived DOTAM-alkyl complexes possess the most favorable properties as potential paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance imaging (MRI) contrast agents. (author)