JACS Article: Hyperpolarized xenon-based molecular sensors for label-free detection of analytes

Hyperpolarized xenon-based molecular sensors for label-free detection of analytes

Praveena D. Garimella, Tyler Meldrum, Leah Suzanne Witus, Monica Smith, Vikram Singh Bajaj, David E Wemmer, Matthew B Francis, and Alexander Pines

ABSTRACT: Nuclear magnetic resonance (NMR) can reveal the chemical constituents of a complex mixture without re- sorting to chemical modification, separation, or other perturbation. Recently, we and others have developed magnetic resonance agents that report on the presence of dilute analytes by proportionately altering the response of a more abun- dant or easily detected species, a form of amplification. One example of such a sensing medium is xenon gas, which is chemically inert and can be optically hyperpolarized, a process that enhances its NMR signal by up to five orders of mag- nitude. Here, we use a combinatorial synthetic approach to produce xenon magnetic resonance sensors that respond to small molecule analytes. The sensor responds to the ligand by producing a small chemical shift change in the Xe NMR spectrum. We demonstrate this technique for the dye, Rhodamine 6G, for which we have an independent optical assay to verify binding. We thus demonstrate that specific binding of a small molecule can produce a xenon chemical shift change, suggesting a general approach to the production of xenon sensors targeted to small molecule analytes for in vitro assays or molecular imaging in vivo.

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