Xenon boost: Medical microfluidics

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  • Published: Jun 1, 2014
  • Channels: NMR Knowledge Base
thumbnail image: Xenon boost: Medical microfluidics

Microfabricated, polarized xenon

A microfluidic device that can detect tiny concentrations of the gas xenon has been developed by US researchers. The device could give a noble boost to biomedical analysis and medical imaging. Image: NIST

A microfluidic device that can generate polarised xenon-129 gas and detect it by nuclear magnetic resonance, NMR, spectroscopy at tiny concentrations has been developed by an international team. The device could give a noble boost to biomedical analysis and medical imaging, according to researchers at the US National Institute of Standards and Technology (NIST) and their colleagues.

Writing in Nature Communications, the team of NIST physicist John Kitching and co-authors from Lawrence Berkeley National Laboratory, the University of California at Berkeley and Bar-Ilan University in Israel describe results of their research part-funded by the US Department of Energy. The new microfluidic chip generates polarized xenon-129 and precludes the need for the ironically car-sized but lamentably non-portable equipment currently required for making the gas in this form. Polarised xenon-129 can be dissolved in liquids and its NMR spectra are altered subtly by the presence of and its interactions with other molecules in complex mixture. Polarized xenon is also being mooted as a useful contrast agent for MRI, magnetic resonance imaging, of the human lungs, for instance.

The team explains that the chip's sensitive internal detector boosts the response of microfluidic NMR on small samples and eliminates the need for the powerful magnets associated with larger NMR devices such as those used in MRI. The researchers add that the microfabricated chip could be mass produced and integrated with existing microfluidic systems readily.

One of a trillion

"We envision this device being an element in a more complex microfluidic NMR system, maybe for medical diagnostics," Kitching suggests. The new device is related to NIST's earlier chip-scale magnetometer but has different applications, of course, and additional capabilities. As with the earlier device, the new chip uses rubidium atoms as magnetometers to detect the xenon polarization. But, the same rubidium atoms are key to polarizing the xenon atoms in the first place to boost their NMR response. The mixture of the rubidium and polarized xenon atoms in the same chamber at the detection stage, gives the NMR signal a 500-fold boost with a field of one micro-Tesla.

The microfluidic device itself is housed in a silicon and glass chip about 30 millimetres long with four small chambers connected by microchannels. In one chamber, circularly polarized light transfers angular momentum to the electrons of the rubidium atoms, a spin exchange with the nuclei of the xenon atoms then ensues. The polarized xenon and rubidium atoms then flow into a detection chamber where a sensor can detect a signal corresponding to fewer than 1 trillion polarized xenon atoms, which is on a par with low-field optical magnetometry.

Portable xenon

"We construct the device using standard microfabrication techniques, which will facilitate its integration with existing microfluidic platforms," the team reports. "This device may enable the implementation of highly sensitive xenon-129 NMR spectroscopy in compact, low-cost, portable devices." Kitching told SpectroscopyNOW that, "The most interesting long-term goal is to achieve integration of the xenon polarizer with more complex microfluidic systems and to demonstrate the dissolution of polarized xenon into a liquid."

Related Links

Nature Commun, 2014, 5, #3908: "Optical hyperpolarization and NMR detection of 129Xe on a microfluidic chip"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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