Xenon for NMR biosensing – Inert but alert

Abstract

NMR studies with hyperpolarized xenon as functionalized sensor or contrast agent recently made notable progress in developing a new approach for detecting molecular markers and parameters of biomedical interest. Combining spin polarization enhancement with novel indirect detection schemes easily enables a 10⁷-fold signal gain, thus having promising potential to solve the NMR sensitivity problem in many applications. Though an inert element, ¹²⁹Xe has exquisite NMR properties to sense molecular environments. This review summarizes recent developments in the production of hyperpolarized xenon and the design and detection schemes of xenon biosensors.

Electron and nuclear spin polarization in Rb-Xe spin-exchange optical hyperpolarization

“…Hyperpolarization also plays a vital role in atomic magnetometry [5], 129 Xe NMR biosensors [6], and many other specialized applications, such as in vivo 129 Xe NMR detection of cells [7], as well as the optical detection of 129 Xe NMR in a microfluidic chip [8]. Spin-exchange optical pumping (SEOP) is an important hyperpolarization (HP) technique [9], in which the unpaired electrons of rubidium atoms are laser polarized, and subsequently, the achieved polarization is transferred to the nuclei of noble-gas atoms in a gas mixture containing the two species, as well as buffer gases such as He and N 2 .…”

Development of an antibody-based, modular biosensor for129Xe NMR molecular imaging of cells at nanomolar concentrations

“…The motivation to develop xenon-based biosensors is twofold. Xenon can be hyperpolarized, enhancing its signal by up to five orders of magnitude and enabling it to be detected at extremely low concentrations (5). In addition, the exquisite sensitivity of xenon to its local chemical environment, as indicated by wellresolved chemical shift changes, brings with it the potential to distinguish not only localization but also specific functional events (6)(7)(8)(9)(10).…”

“…However, in the past few years, the scope for using 129 Xe for targeted biosensor imaging has notably increased (5). The motivation to develop xenon-based biosensors is twofold.…”

NMR Hyperpolarization Techniques of Gases

“…$20/L). The selected applications described here include functional lung imaging, [22] metabolic brown fat imaging, [23] and biosensors [24] (including those enabled by genetic encoding [25] ). A recent demonstration of the DNP process to hyperpolarize 129 Xe [26] and hydrocarbon gases [27] is also described.…”