Effects of membrane viscoelasticity on the red blood cell dynamics in a microcapillary.

The mechanical properties of red blood cells (RBCs) play key roles in their biological functions in microcirculation. In particular, RBCs must deform significantly to travel through microcapillaries with sizes comparable with or even smaller than their own. Although the dynamics of RBCs in microcapillaries have received considerable attention, the effect of membrane viscoelasticity has been largely overlooked.

Cytoskeletal Contribution to Cell Stiffness Due to Osmotic Swelling; Extending the Donnan Equilibrium.

Cell volume regulation is commonly analyzed with a model of a closed semipermeable membrane filled with impermeant mobile solutes and the Donnan Equilibrium is used to predict the hydrostatic pressure. This traditional model ignores the fact that most cells are filled with a crosslinked cytoskeleton that is elastic and can be stretched or compressed like a sponge with no obvious need to move mobile solutes. However, calculations show that under osmotic stress, the elastic energy of the cytoskeleton is far greater than the elastic energy of the membrane.