Low-field 1H NMR parameterization of model cell suspensions. A diffusion and relaxation study

Introduction:
Nuclear magnetic resonance (NMR) is a powerful method for the non-invasive study of a wide range of objects. Among its many characteristics, molecular diffusion can be examined without the need for any chemical or isotopic tracers by applying magnetic field gradients within the NMR sequence. Aim: In our study, model cell suspensions were characterized by means of low-field (LF) (0.05 T) 1H NMR relaxometry. The proposed multi-parametric characterization based on independent 2D T1-T2 and D-T2 measurements was implemented to obtain a set of MR parameters as a specific signature for model cells.

Material and methods:
The D-T2 and T1-T2 correlation measurements were conducted on yeast samples with different amounts of added water. Signals from intracellular and extracellular water compartments and free water were identified on D-T2 maps and their diffusion coefficients were extracted.

Results:
Mean D_IC was equal to 8.4 × 10^–11 m²/s and mean D_EC ranged from 1.0 × 10^–9 m²/s to 1.65 × 10^–9 m²/s. T1/T2 ratio was calculated and for IC space values in the range of 4.2–5.3 were observed. Finally, we demonstrated the possibility of detecting signals from cells for the samples with a low concentration of cell suspensions or a small amount of the sample.

Conclusions:
These findings are promising for more complex cell investigations in vitro and in vivo, without any contrast agents, applying solely biomarkers.