Neurotransmitter-Responsive Nanosensors for -Weighted Magnetic Resonance Imaging.

Neurotransmitter-sensitive contrast agents for magnetic resonance imaging (MRI) have recently been used for mapping signaling dynamics in live animal brains, but paramagnetic sensors for -weighted MRI are usually effective only at micromolar concentrations that themselves perturb neurochemistry. Here we present an alternative molecular architecture for detecting neurotransmitters, using superparamagnetic iron oxide nanoparticles conjugated to tethered neurotransmitter analogs and engineered neurotransmitter binding proteins. Interactions between the nanoparticle conjugates result in clustering that is reversibly disrupted in the presence of neurotransmitter analytes, thus altering -weighted MRI signals.