Xenon-129 NMR as applied to remote detection and to the xenon biosensor

Applications of hyperpolarized 129Xe to remote detection and the xenon biosensor are developed. Remote detection NMR is a novel technique developed to enhance the sensitivity of spectroscopic and imaging magnetic resonance experiments by spatially separating the encoding and detection steps. This technique is optimal for systems with low fill factors, (the sample volume to coil volume ratio) such as fluid flow through porous media, where the samples geometry inherently limits the fill factor. The experimental setup consists of a large imaging coil that encodes signal at any point in the sample using selective excitation and field gradients. The encoded information is stored as magnetization and travels with the fluid out of the sample where it is detected by a specialized coil that provides a good fill factor for the fluid. Using this technique we have obtained remarkable flow images of hyperpolarized 129Xe in a porous rock sample as well as in a glass vessel. This technique allows for monitoring of the time-of-flight (TOF), i.e. how long it takes the gas from a specific location in the sample to reach the detector after the encoding step. Since the gas is detected transiently, information about the dispersion of the gas as it travels from the encoding location to the detector is also obtained. The xenon biosensor is composed of a cryptophane-A cage that binds xenon and is linked to biotin via a chain of amino acids. When biotin binds avidin the chemical shift of xenon inside the cage changes signaling the binding occurrence between biotin and avidin. New approaches such as employing an optimized xenon delivery flow system, using the exchange properties of xenon in and out of the cage and constructing biosensors with optimized characteristics for detection are developed to lower the detection limit of the biosensor.