Relaxometric evaluation of novel manganese(II) complexes for application as contrast agents in magnetic resonance imaging.
Three novel Mn(II) complexes bearing benzyloxymethyl functionalities are reported and their ability to enhance water (1H and 17O) relaxation times is investigated in detail. Two of them contain one coordinated water molecule and display relaxivity values only slightly smaller than those shown by the most clinically used contrast agents (e.g. [Gd(DTPA)(H2O)]2-). Moreover, in these Mn(II) chelates the exchange rate of the coordinated water is ca. one order of magnitude higher if compared to the exchange rates previously reported for Gd(III) complexes with octadentate ligands. The occurrence of such fast exchange rates of the coordinated water is exploited in the formation of macromolecular adducts with human serum albumin to attain systems displaying relaxivity values in the upper range of those so far reported for analogous Gd(III) systems. These results strongly support the view that Mn(II) complexes, in spite of the lower effective magnetic moment, can be considered as viable alternatives to the currently used Gd(III) complexes as contrast agents for MRI applications.
Aime
Silvio
S
Dipartimento di Chimica IFM, Università di Torino, Via P. Giuria 7, 10125 Turin, Italy. aime@silver.ch.unito.it
Anelli
Lucio
L
Botta
Mauro
M
Brocchetta
Marino
M
Canton
Simonetta
S
Fedeli
Franco
F
Gianolio
Eliana
E
Terreno
Enzo
E
D002614:Chelating Agents / Q000737:chemistry* / Q000378:metabolism; D003287:Contrast Media / Q000737:chemistry*; D005069:Evaluation Studies as Topic; D005682:Gadolinium / Q000737:chemistry; D006801:Humans; D046911:Macromolecular Substances; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D009942:Organometallic Compounds / Q000737:chemistry / Q000378:metabolism; D011199:Potentiometry / Q000379:methods; D012709:Serum Albumin / Q000378:metabolism*; D014867:Water / Q000737:chemistry
D002614:Chelating Agents; D003287:Contrast Media; D046911:Macromolecular Substances; D009942:Organometallic Compounds; D012709:Serum Albumin; D014867:Water; D008345:Manganese; D005682:Gadolinium