A novel series of complexones with bis- or biazole structure as mixed ligands of paramagnetic contrast agents for MRI |
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Authors: | Mayoral Elena P García-Amo María López Pilar Soriano Elena Cerdán Sebastián Ballesteros Paloma |
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Institution: | a Departamento Química Orgánica y Biología, Facultad de Ciencias, UNED, Senda del Rey 9, 28040, Madrid, Spain b Instituto de Investigaciones Biomédicas CSIC, c/ Arturo Duperier 4, 28029, Madrid, Spain |
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Abstract: | We describe the syntheses, physicochemical properties and biological evaluation of a novel series of complexones containing bis- or biazoles moieties and two iminodiacetic acid units as novel ligands for paramagnetic lanthanides. The complexones were prepared by reaction of the corresponding 1,1′-bishaloethylbi- or bispyrazoles with methyl iminodiacetate and subsequent NaOH hydrolysis. 1,1′-Bisbromoethyl precursors were obtained by direct alkylation with an excess of 1,2-dibromoethane, or by heating the corresponding alcohol in HCl. Sigmoidal binding isotherms and MO calculations supported as most stable structures in solution, those containing two Gd(III) atoms bound per molecule of complexone with half saturation values S0.5 (M?1, 22 °C, pH 7.2) in the range 6.5 10?60.5<36.1 10?6. Relaxivity properties r1, r2, s?1 mM?1 Gd(III)] determined at 1.5 Tesla gave values (12.0<r1<17.7, 12.2<r2<20), improving significantly the relaxivities of reference compounds such as Gd(III)EDTA (5.2, 5.6) or Gd(III)DTPA (4.30, 4.30). These improvements involve mainly increased hydration and slower rotational motions. In vitro toxicity experiments are reported. |
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