A low-molecular-weight ditopic MRI probe for ratiometric sensing of zwitterionic amino acid neurotransmitters.

We report a novel ditopic Gd(iii)-based probe selective to zwitterionic amino acid neurotransmitters (ZNTs) crafted for ratiometric MRI imaging. The probe displayed increased binding affinity to ZNTs and non-synchronized concentration-dependent changes of the r1- and r2-relaxivity. Through the application of a T2/T1 weighted MRI strategy, we demonstrated signal enhancement for cooperatively bound glutamate and γ-aminobutyric acid ZNTs over competitive hydrogencarbonate, which remained MR silent.