Hyperpolarized Xenon Biosensors and HyperCEST
Xenon based biosensors are molecules that couple target binding events to NMR detection of specifically associated changes in xenon NMR signals. There are many variations that enable high sensitivity detection of the presence of target molecules though changes in the chemical shift of xenon, or the spatial distribution of such molecules when biosensors are tethered to a target. The strong NMR signals that can be obtained through hyperpolarization of xenon, and amplification by chemical exchange, allow detection of molecules at nanomolar concentrations and below, far lower than the normal limit for NMR. The variety of sensors that have already been constructed is reviewed, and shows that the principles are quite general, and xenon biosensors should be applicable in many chemical and biological sensing applications. Xenon biosensor development remains an active area, new ways of targeting are being developed, and further optimizations may yield even higher sensitivity.