Anisotropic diffusion in stretched hydrogels containing erythrocytes: evidence of cell-shape distortion recorded by PGSE NMR spectroscopy.

The remarkable flexibility of human red blood cells (RBCs) allows them to assume a range of shapes in normal and disease states. Biochemical mechanisms and energetic requirements associated with changes in RBC geometry are not well understood because of a lack of experimental procedures to fix and study cells in different morphological forms. By incorporating RBCs into stretchable gelatin hydrogels, we created conditions for adjustable elongation of their normal discocytic shape in all orientations. As the RBC-containing gels were stretched or compressed, the changes in the cell morphology were studied by using H-PGSE-NMR spectroscopy. Measurements of the apparent diffusion coefficient of water along the three orthogonal directions revealed tuneable anisotropy in the environment of the hydrogel samples. Light microscopy was also used for recording the extent to which RBCs were distorted in a stretched gel that had been set around them. Having demonstrated the applicability of NMR diffusometry to detect morphological changes of immobilised cells, we have laid the groundwork for future investigations of controllably distorted RBCs. Specifically, we expect studies of metabolic and biophysical properties of the physically deformed cells, thus inferring the connection between intracellular physico-chemical processes and RBC morphology. Copyright © 2016 John Wiley & Sons, Ltd.