In vitro characterization of an Fe8 cluster as potential MRI contrast agent

The complex [(tacn)(6)Fe-8(mu(3)-O)(2)(mu(2)-OH)(12)]Br(8)(.)9H(2)O (Fe-8) was evaluated in vitro as a new kind of possible MRI contrast agent. Relaxivities were measured at 1.41 and 9.4T for Fe-8 and commercial Gd-DTPA dissolved in PBS. There was significant difference for r(1) and r(2) values between Fe-8 and Gd-DTPA at high field (9.4T) and for r(1) at low field (1.4 T) (p < 0.05). Phantom studies with T-1-weighted MRI at 9AT suggest T-1 contrast potential for Fe-8. That is, up to 5.2 times higher intensity enhancement with respect to that of equimolar Gd-DTPA was obtained with an Fe-8 concentration, referred to the whole molecule, of 0.2 mm, for which no toxicity on C6 cells could be detected. No toxic effects on cultured C6 cells were observed up to a concentration of 1 mm Fe-8. Copyright (c) 2005 John Wiley & Sons, Ltd.