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Towards Targeted MRI: New MRI Contrast Agents for Sialic Acid Detection
Author(s) -
Frullano Luca,
Rohovec Jan,
Aime Silvio,
Maschmeyer Thomas,
Prata M. Isabel,
de Lima J. J. Pedroso,
Geraldes Carlos F. G. C.,
Peters Joop A.
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400369
Subject(s) - sialic acid , chemistry , boronic acid , phenylboronic acid , selectivity , carboxylate , moiety , amide , adduct , gadolinium , stereochemistry , biochemistry , combinatorial chemistry , organic chemistry , catalysis
The detection of sialic acid in living systems is of importance for the diagnosis of several types of malignancy. We have designed and synthesized two new lanthanide ion ligands (L 1 and L 2 ) that are capable of molecular recognition of sialic acid residues. The basic structure of these ligands consists of a DTPA‐bisamide (DTPA, diethylenetriamine pentaacetic acid) whose amide moieties each bear both a boronic function for interaction with the diol groups in the side chain of sialic acid, and a functional group that is positively charged at physiologic pH values and is designed to interact with the carboxylate anion of sialic acid. The relaxometric properties of the Gd 3+ complexes of these two ligands were evaluated. The relaxivity of the GdL 1 complex has a significant second‐sphere contribution at pH values above the p K a of its phenylboronic acid moiety. The interaction of the Gd 3+ complexes of L 1 and L 2 with each of several saccharides was investigated by means of a competitive fluorescent assay. The results show that both complexes recognize sialic acid with good selectivity in the presence of other sugars. The adduct formed by GdL 2 with sialic acid has the higher conditional formation constant (50.43±4.61 M −1 at pH 7.4). The ability of such complexes to recognize sialic acid was confirmed by the results of a study on the interaction of corresponding radiolabeled complexes ( 153 SmL 1 and 153 SmL 2 ) with C6 glioma rat cells. 153 SmL 2 in particular is retained on the cell surface in significant amounts.