Loading and relaxation dynamics of a red blood cell

Area of Science:

• Biophysics
• Computational Biology
• Materials Science

Background:

• Red blood cells (RBCs) are crucial for oxygen transport and their mechanical properties are vital for circulation.
• Understanding RBC dynamics under mechanical stress is essential for diagnosing and treating various blood disorders.

Purpose of the Study:

• To investigate the unsteady dynamics of a single red blood cell (RBC) under external mechanical loads using numerical simulations.
• To compare the loading (L) and relaxation (R) dynamics of RBCs and analyze their characteristic times (t_L and t_R).
• To elucidate the non-universal characteristics of RBC membrane response to mechanical loads.

Main Methods:

• Mesoscale numerical simulations were employed to model RBC behavior.
• Comparison of loading and relaxation dynamics under various mechanical loads (stretching, shear, elongational flow).
• Analysis of characteristic times (t_L, t_R), membrane viscosity, and elastic shear modulus.

Main Results:

• At low mechanical loads, RBC loading and relaxation dynamics are symmetrical (t_L≈t_R) and load-independent.
• At higher loads, an asymmetry emerges where loading dynamics are faster than relaxation dynamics (t_L < t_R).
• This asymmetry exhibits non-universal behavior, depending on load intensity and RBC membrane viscoelastic properties.

Conclusions:

• RBCs exhibit distinct loading and relaxation dynamics, with loading typically being faster.
• The non-universal nature of this asymmetry is influenced by membrane viscosity and elastic shear modulus.
• Provides quantitative insights into RBC membrane response to transient mechanical loads.