Article published NMR
High resolution for very small samples
A micro-detector analyzes solid and/or very low quantity samples using Nuclear Magnetic Resonance (NMR). This technology paves the way for several industrial applications and research in biology, biochemistry, pharmacy, materials, etc.
Nuclear Magnetic Resonance (NMR) is a particularly advantageous analysis technique since it is entirely non-invasive: based on the magnetic properties in atom nuclei, it provides 3D images of the inside of a liquid or solid structure.
Localized spectroscopy using NMR thus provides information about the chemical composition at each point. But it has its limits: "It has relatively low sensitivity and requires several hours to acquire enough data to obtain a quality spectrum when the sample to be analysed is not a consistent fluid but rather a small quantity of solid or heterogeneous material," explains Dimitrios Sakellariou, who, alongside Jacques-François Jacquinot, a fellow researcher at Iramis*, has filed two patents for an extraordinarily innovative NMR concept. It makes it possible to analyse this type of sample, in a few seconds, on the nanolitre scale. For these specific cases, low-sensitivity static detectors were developed, based on "Magic Angle Spinning" - where the sample is spun around itself at a rate of a few thousand spins per second at an angle of 54.7° to the magnetic field axis. "Our solution, named MACS (Magic Angle Coil Spinning) is based on this concept,"** explains Dimitrios Sakellariou. "It could be ten times more sensitive, or even more, since the detection process takes place closer to the sample."
Increased performance, reduced cost
The major advantage presented by the solution: it can be adapted to commercial NMR devices. "We had the idea of spinning the micro-sample inside this fixed detector," he continues. "For each micro-sample, we design a micro-coil specially adapted to its size. This micro-detector spins with the sample, and sends and receives information by radiofrequency to the fixed detector." The simplicity of this solution, which is both high-performance and economical, paves the way for several further potential applications.Example: in the biomedical sector, for micro-biopsy studies in hospitals, analyses of small quantities of proteins, metabolomics (analysis of metabolites - transformation products - in a biological tissue), for the study of a small number of cells or even heat-sensitive or frozen biological samples, etc.
In the chemical industry, such solutions make it possible to study hazardous materials that we need to handle in very small quantities, such as radioactive material, explosives or toxic biological material like prions. "Furthermore, the sample-holder can be considered as the containment barrier," adds Dimitrios Sakellariou. The pharmaceutical industry can thus study, at high speed, the activity of solid medicines according to their crystalline form or analyse "labs-on-chips" by NMR.
*Institute for the irradiation of matter at Saclay.
** D. Sakellariou et al., Nature 447, 694-697, 2007.
