Two-For-One Bioimaging Agent

A novel bimetallic complex could be used as a contrast agent for both luminescence microscopy and magnetic resonance imaging (MRI), two powerful biological imaging methods that usually require different imaging agents. Stephen Faulkner of the University of Manchester, in England, and coworkers describe the spectroscopic properties of the potential imaging agent (shown), which contains a luminescent rhenium chromophore in combination with a gadolinium macrocycle that is typically used as an MRI contrast agent (J. Am. Chem. Soc., DOI: 10.1021/ja710859p). The luminescence lifetime of the molecule lasts long enough to overcome any short-lived background fluorescence, and the molecule's luminescence response is linear over a broad concentration range, from subnanomolar to 100 μM. But the MRI contrast of the bimetallic complex is likely to be poor at submicromolar concentrations, the researchers note. They hope to develop additional complexes that can provide MRI contrast at nanomolar concentrations, possibly by adding more gadolinium ions.