Towards single egg toxicity screening using microcoil NMR

Abstract

Planar microcoils with diameter ranging from 20 to 1000 μm I.D. (130-1130 μm O.D.) are evaluated for their applications in NMR spectroscopy. The coils are first overfilled with a standard sucrose solution and compared against each other. Coils with smaller I.D. (≤100 μm) perform extremely well. One hypothesis is that as the coils get smaller the volume occupied by the copper turns increases relative to the open I.D.; as such a large proportion of the sample is brought in close proximity to the coil turns and likely gives rise to strong sample-coil magnetic coupling, which increases the signal. The applications of the planar microcoils are demonstrated on Cypselurus poecilopterus (fish) and Daphnia magna (water flea) eggs. A single D. magna egg on a 50 μm coil yielded at least 3000 times the mass sensitivity (∼9,000,000 time saving) when compared to a 5 mm probe. This value could be at least 4 times higher if the B homogeneity of the coils could be improved. With the current design, 80% of the signal is lost in multiple pulse experiments that rely on phase inversion and signal cancellation between scans. The data were extrapolated to predict that biological samples as small as ∼4 μm may become accessible via planar microcoil designs. To fulfill their potential for in situ metabolic screening, specialized magnetic susceptibility matched sample holders that restrict the sample to the homogeneous B field region (i.e. within the 90% RF field) of the coil and advanced experiments that narrow spectral lines, suppress lipids and disperse signals into multiple dimensions will be required.

Flow‐based in vivo NMR spectroscopy of small aquatic organisms

“…Data were collected at 500 MHz using a prodigy TCI cryoprobe. Adapted from Fugariu et al with the permission from Wiley and experimental details can be found in Fugariu et al…”

“…Data were collected at 500 MHz using a prodigy TCI cryoprobe. (a) Conventional 1 H spectrum, (b) IP-iSQC spectrum before tilting, (c) after tilting, (d) projection from C that is analogous to a 1 H spectrum in a well-shimmed field [60] with the permission from Wiley and experimental details can be found in Fugariu et al [59] [59] Experimental details can be found in Fugariu et al [59] (Note: A complete package, including all pulse programs, au programs, and instructions to run IP-iSQC are available from the authors of this tutorial on request) times or more biomass compared with a conventional proton experiment.…”

In-Vivo NMR Spectroscopy: A Powerful and Complimentary Tool for Understanding Environmental Toxicity

“…However, 2D NMR examining the correlation between 1 H- 1 H and 1 H- 13 C offers additional spectral dispersion for molecular fingerprinting and connectivity information for molecular assignment [ 79 ]. NMR is a tool that can be used with varying amounts of sample (even down to sub-nL eggs) [ 80 , 81 , 82 ], is a non-destructive technique, and is highly reproducible across samples and labs [ 83 , 84 , 85 , 86 ]. NMR is also fully quantitative and when applied appropriately, each nuclei gives the same response in the spectrum leading to accurate quantitation of unknowns without the need for internal standards [ 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 ].…”

NMR microsystem for label-free characterization of 3D nanoliter microtissues

“…However, due to limitations of the current commercial hardware, magnetic resonance cannot be routinely applied to in-vivo and in-vitro studies at the nanoliter (nL) scale, typical of microorganisms and cell cultures. Indeed, micro-NMR is a longstanding technical challenge, and numerous researchers have proposed methods to achieve it, mainly using micro solenoids 6,7 , planar micro coils 8 , magic angle coil spinning (MACS) probes at ultra-high fields 9 , reaching sample volume sizes of about 10 nL. More recently, NMR spectroscopy of eggs of microorganisms having a volume of just 0.1 nL was reported in a relatively weak field strength of 7 T. Such advancement was possible thanks to a novel approach based on complementary metal-oxide semiconductor (CMOS) microchips that delivered high sensitivity, robustness, and a local and easily accessible sensing region 10 .…”