Magnetic resonance imaging excels at anatomy but struggles with chemistry: the molecules that actually drive neural computation are largely invisible to it. Bioengineers led by Alan Jasanoff at MIT's McGovern Institute for Brain Research have narrowed that gap with a new class of sensors reported in Nature Biomedical Engineering, in work spearheaded by postdoc Sayani Das and graduate student Jacob Cyert Simon.
The sensors, called liposomal nanoparticle reporters, are tiny lipid sacs packed with gadolinium, a standard MRI contrast agent. Water channels embedded in their walls open or close depending on whether a target molecule is present; when water floods in, the local MRI signal brightens, while alternative designs dim it instead. Because a single target molecule gates the behaviour of many gadolinium units at once, the response is strongly amplified compared with conventional one-to-one contrast agents.
In living rats, experiments led by postdoc Miranda Dawson detected biotin at micromolar concentrations with about tenfold greater sensitivity than conventional sensors, and the particles can be delivered systemically and distribute throughout the brain. The team's next targets are dopamine and glutamate, pointing towards brain-wide maps of the neurotransmitters and metabolites that underpin cognition, with obvious value for studying psychiatric and neurodegenerative disease.