Handheld spectroscopy devices could soon become real

Nuclear magnetic resonance (NMR) is an analytical tool with a wide range of applications including magnetic resonance imaging which is used for diagnostic purposes in medicine. However, NMR often requires the generation of strong magnetic fields, which limits the scope of its use. Researchers working at the Johannes Gutenberg University Mainz (JGU) and the Helmholtz Institute Mainz (HIM) have now discovered potential new ways reduce the size of the corresponding devices as well as the possible associated risk by eliminating the need for strong magnetic fields. This is achieved by combining so-called zero to ultra-low field NMR with a special hyperpolarization technique. “This exciting new method is based on an innovative concept. It opens up a whole range of opportunities and overcomes previous drawbacks,” said Dr. Danila Barskiy, Sofja Kovalevskaja award winner who has been working in the relevant discipline at JGU and HIM since 2020.

New approach to enable measurements without strong magnetic fields

The current generation of NMR devices is, because of the magnets, extremely heavy and expensive. Another complicating factor is the current shortage of liquid helium used as a refrigerant. “With our new technique, we are gradually moving towards a completely magnetless ZULF NMR status, but we still have many challenges to overcome,” Barskiy said.

To make magnets redundant in this context, Barskiy came up with the idea of ​​combining zero-to-ultra-low-field nuclear magnetic resonance (ZULF-NMR) with a special technique that allows atomic nuclei to be hyperpolarized. ZULF NMR itself is a recently developed form of spectroscopy that provides abundant analytical results without the need for large magnetic fields. Another advantage over high-field NMR is that its signals can also be easily detected in the presence of conductive materials, such as metals. The sensors used for ZULF NMR, usually optically pumped magnetometers, are very sensitive, easy to use and already commercially available. Thus, it is relatively simple to assemble a ZULF NMR spectrometer.

SABER-Relay: Transfer the order of rotation like a stick

However, the generated NMR signal is a problem to be addressed. The methods that have been used to date to generate the signal are only suitable for the analysis of a limited selection of chemicals or are otherwise associated with exorbitant costs. For this reason, Barskiy decided to exploit the SABER hyperpolarization technique which allows the alignment of nuclear spins in large numbers in solution. There are a number of such techniques that would produce sufficient signal for detection under ZULF conditions. Of these, SABRE, short for Signal Amplification by Reversible Exchange, has proven particularly well suited. At the heart of the SABER technique is an iridium metal complex that provides spin order transfer from parahydrogen to a substrate. Barskiy managed to circumvent the disadvantages resulting from the temporary binding of the sample to the complex by employing SABER-Relay, a very recent improvement of the SABER technique. In this case, SABER is used to induce a bias which is then relayed to a secondary substrate.

Spin chemistry at the interface of physics and chemistry

In their article entitled “Relayed Hyperpolarization for Zero-Field Nuclear Magnetic Resonance” published in Scientists progress, Barskiy, lead author Erik Van Dyke and their co-authors explain how they were able to detect methanol and ethanol signals extracted from a vodka sample. “This simple example shows how we were able to extend the range of applications of ZULF NMR using an inexpensive, fast, and versatile hyperpolarization method,” Barskiy summarized. “We hope that we have managed to get a little closer to our goal of making possible the development of compact and portable devices that can be used for the analysis of liquids such as blood and urine and, in the future , possibly allowing the discrimination of particular chemicals, such as glucose and amino acids.”

Barskiy won a Sofja Kovalevskaja Prize from the Alexander von Humboldt Foundation in 2020 and therefore moved from the University of California, Berkeley to Mainz, where he began research in Professor Dmitry Budker’s group at the JGU Institute of Physics and HIM. Barskiy is active in the field of physical chemistry and leads a research group focused on the possible applications of NMR in chemistry, biology and medicine.

– This press release was originally published on the website of Johannes Gutenberg University Mainz

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