NMR spectroscopy of single sub-nL ova with inductive ultra-compact single-chip probes

Marco Grisi,Beatrice Volpe,Nicola Harris,Franck Vincent,Roberto Guidetti,Armin Beck,Giovanni Boero

doi:10.1038/srep44670

Abstract

Nuclear magnetic resonance (NMR) spectroscopy enables non-invasive chemical studies of intact living matter. However, the use of NMR at the volume scale typical of microorganisms is hindered by sensitivity limitations, and experiments on single intact organisms have so far been limited to entities having volumes larger than 5 nL. Here we show NMR spectroscopy experiments conducted on single intact ova of 0.1 and 0.5 nL (i.e. 10 to 50 times smaller than previously achieved), thereby reaching the relevant volume scale where life development begins for a broad variety of organisms, humans included. Performing experiments with inductive ultra-compact (1 mm2) single-chip NMR probes, consisting of a low noise transceiver and a multilayer 150 μm planar microcoil, we demonstrate that the achieved limit of detection (about 5 pmol of 1H nuclei) is sufficient to detect endogenous compounds. Our findings suggest that single-chip probes are promising candidates to enable NMR-based study and selection of microscopic entities at biologically relevant volume scales.

Highlights

Nuclear magnetic resonance (NMR) is a well-established spectroscopic technique widely employed in physics, chemistry, medicine, and biology
In this work we report, for the first time, NMR-based spectroscopy of single untouched sub-nL ova, describing experiments on the tardigrade Richtersius coronifer (Rc) and the nematode Heligmosomoides polygyrus bakeri (Hp)
Repeated experiments suggest that the linewidth measured in Rc ova is intrinsically related to the sample, probably resulting from microscopic constituents of the ovum introducing susceptibility mismatches whose typical spatial distribution impedes field shimming in the intracellular region

Summary

Introduction

Nuclear magnetic resonance (NMR) is a well-established spectroscopic technique widely employed in physics, chemistry, medicine, and biology. Questions concerning invasivity stimulated the coin of the biological equivalent of the so called observer effect, referring to the inability to separate a measurement from its potential influence on the observed cell[9] In this regard, NMR is one of the most promising techniques for studies of intracellular compounds in untouched living entities (i.e., with extremely weak physical and chemical perturbations)[1,7]. In this work we report, for the first time, NMR-based spectroscopy of single untouched sub-nL ova, describing experiments on the tardigrade Richtersius coronifer (Rc) and the nematode Heligmosomoides polygyrus bakeri (Hp). This setup systematically allows for experimental times as long as one day

Methods

Results

Conclusion