ABSTRACT
Our work, as magnetic resonance imaging (MRI) probe developers,
was always frustrated by the drawbacks that relaxation enhancers
have with respect to the colored reporters biologists dealt with
in their confocal images. In fact, our beloved paramagnetic agents
fail when two of them are targeted to different epitopes in the
same anatomical region. Their presence is indistinguishable in
an MR image, as they simply add their effect on water proton
relaxation rates. Moreover, also for the class of Gd-based responsive
agents (where chemists have identified a number of modes to
make the observed relaxivity responsive to specific physicochemical
and biological parameters), there were problems because their in
vivo exploitation required the knowledge of the local concentration
in order to monitor the variable of interest from the relaxation
enhancement values.
