Exploring the Potential of Broadband Complementary Metal Oxide Semiconductor Micro-Coil Nuclear Magnetic Resonance for Environmental Research

With sensitivity being the Achilles' heel of nuclear magnetic resonance (NMR), the superior mass sensitivity offered by micro-coils can be an excellent choice for tiny, mass limited samples such as eggs and small organisms. Recently, complementary metal oxide semiconductor (CMOS)-based micro-coil transceivers have been reported and demonstrate excellent mass sensitivity. However, the ability of broadband CMOS micro-coils to study heteronuclei has yet to be investigated, and here their potential is explored within the lens of environmental research. Eleven nuclei including 7Li, 19F, 31P and, 205Tl were studied and detection limits in the low to mid picomole range were found for an extended experiment. Further, two environmentally relevant samples (a sprouting broccoli seed and a D. magna egg) were successfully studied using the CMOS micro-coil system. 13C NMR was used to help resolve broad signals in the 1H spectrum of the 13C enriched broccoli seed, and steady state free precession was used to improve the signal-to-noise ratio by a factor of six. 19F NMR was used to track fluorinated contaminants in a single D. magna egg, showing potential for studying egg-pollutant interactions. Overall, CMOS micro-coil NMR demonstrates significant promise in environmental research, especially when the future potential to scale to multiple coil arrays (greatly improving throughput) is considered.

P-262 Magnetic Resonance spectroscopy of individual mammalian embryos and human microtissues

Study question

Can magnetic resonance unravel the metabolic fingerprint of samples at the embryo scale?

Summary answer

We successfully utilized Magnetic Resonance Spectroscopy (MRS) on single mammalian embryos and microtissues and observed a diverse range of lipids in less than 1 hour.

What is known already

Non-invasive selection of the best embryo to transfer is one of the most significant challenges for ART professionals. The chemical sensitivity, resolving power, and, more importantly, the non-invasive nature of MRS makes it an excellent candidate to investigate the building blocks of complex organisms. Although MRS is a well-established technique for the biochemical profiling of large organisms, handling small samples like embryos and 3D cell cultures and spheroids alongside sensitivity issues has prevented its adoption for clinical and research applications. Our group has overcome these limitations with microchip-based sensors to leverage non-invasive MRS technology down to the embryo scale.

Study design, size, duration

A NASH in vitro model of liver microtissues was used first to detect lipid-based metabolic biomarkers over multiple time points in complex 3D cell cultures such as microtissues. We could discriminate between healthy and diseased human micro-livers based on their lipid content. Once the MRS data acquisition and analysis were set up using stimulated or control samples, we moved to the single early or late arrested bovine embryo analysis. The whole experiment lasted one month.

Participants/materials, setting, methods

Early or late arrested bovine embryos were obtained through IVF, cryopreserved and measured shortly after thawing. The microtissues were provided by InSphero AG (Schlieren, CH) and individually measured fresh in a time frame of 14 days based on 117 measurements. The micro-MRS device was loaded with culture medium and a single sample, then loaded into the MRS magnet. Measurements were performed for a total time of 50 min per embryo or 15 min per microtissue.

Main results and the role of chance

Micro-MRS efficiently identified four different biomarkers that were significantly differently expressed (p < 0.05) according to the biological state of microlivers simulating non-alcoholic fatty liver disease (NAFL). Three of these markers represent relative concentrations of lipid signatures from fully saturated, mono and poly-unsaturated fatty acids. In addition, we analyzed in vitro produced pre-implantation bovine embryos naturally arrested at different developmental stages. This choice arose from the necessity to analyze them at different and fixed developmental stages to investigate our technology discrimination potential. The spectra obtained from the embryos present up to 6 peak regions assignable to fatty acids as observed in microtissues. Furthermore, the amplitude of the peaks varies substantially within the same group, i.e., within the morulae and within the two 2-cell stage arrested embryos. Using both microtissues and mammalian embryos, we demonstrated that micro-MRS could be used to investigate variations in the lipid content of tiny samples non-invasively. Generally, the majority of the analytical assays used in lipid metabolism investigations rely on invasive/destructive methods such as histology and biopsies, which would hinder the continuation of embryonic development. A non-invasive in vivo assay like the one presented here would provide the means to reveal the role of embryonic lipids throughout development.

Limitations, reasons for caution

A vital step towards establishing MRS as a clinical and research tool is the reliable detection of a wide range of signals from cellular components. Our method is ready for R&D studies, while its clinical application requires further safety studies and protocol optimization.

Wider implications of the findings

A non-invasive quick assay would provide the means to reveal the role of embryonic lipids throughout development. Micro-MRS can further develop into a safe embryo assay for selection before embryo transfer. This would apply to both human and animal ART, whose success rate is relatively low.

Trial registration number

not applicable

NMR spectroscopy of a single mammalian early stage embryo

The resolving power, chemical sensitivity and non-invasive nature of NMR have made it an established technique for in vivo studies of large organisms both for research and clinical applications. NMR would clearly be beneficial for analysis of entities at the microscopic scale of about 1 nL (the nanoliter scale), typical of early development of mammalian embryos, microtissues and organoids: the scale where the building blocks of complex organisms could be observed. However, the handling of such small samples (about 100 µm) and sensitivity issues have prevented a widespread adoption of NMR. In this article we show how these limitations can be overcome to obtain NMR spectra of a mammalian embryo in its early stage. To achieve this we employ ultra-compact micro-chip technologies in combination with 3D-printed micro-structures. Such device is packaged for use as plug & play sensor and it shows sufficient sensitivity to resolve NMR signals from individual bovine pre-implantation embryos. The embryos in this study are obtained through In Vitro Fertilization (IVF) techniques, transported cryopreserved to the NMR laboratory, and measured shortly after thawing. In less than 1 h these spherical samples of just 130-190 µm produce distinct spectral peaks, largely originating from lipids contained inside them. We further observe how the spectra vary from one sample to another despite their optical and morphological similarities, suggesting that the method can further develop into a non-invasive embryo assay for selection prior to embryo transfer.

Resolving an individual one-proton spin flip to determine a proton spin state

Previous measurements with a single trapped proton (p) or antiproton (p) detected spin resonance from the increased scatter of frequency measurements caused by many spin flips. Here a measured correlation confirms that individual spin transitions and states are rapidly detected instead. The 96% fidelity and an efficiency expected to approach unity suggests that it may be possible to use quantum jump spectroscopy to measure the p and p magnetic moments much more precisely.

One-particle measurement of the antiproton magnetic moment

For the first time a single trapped antiproton (p) is used to measure the p magnetic moment μ(p). The moment μ(p)=μ(p)S/(ℏ/2) is given in terms of its spin S and the nuclear magneton (μ(N)) by μ(p)/μ(N)=-2.792 845±0.000 012. The 4.4 parts per million (ppm) uncertainty is 680 times smaller than previously realized. Comparing to the proton moment measured using the same method and trap electrodes gives μ(p)/μ(p)=-1.000 000±0.000 005 to 5 ppm, for a proton moment μ(p)=μ(p)S/(ℏ/2), consistent with the prediction of the CPT theorem.