Viscoelastic phenotyping of red blood cells

• Red blood cells (RBCs) are the simplest cell types with complex dynamical and viscoelastic phenomenology. While the mechanical rigidity and the flickering noise of RBCs have been extensively investigated, an accurate determination of the constitutive equations of the relaxational kinetics is lacking. Here we measure the force relaxation of RBCs under different types of tensional and compressive extension-jump protocols by attaching an optically trapped bead to the RBC membrane. Relaxational kinetics follows linear response from 60 pN (tensional) to similar to 20 pN (compressive) applied forces, exhibiting a triple exponential function with three well-separated timescales over four decades (0.01-100 s). While the fast timescale (tau(F) similar to 0.02(1) s) corresponds to the relaxation of the membrane, the intermediate and slow timescales (tau(I) = 4(1) s; tau(S) = 70(8) s) likely arise from the cortex dynamics and the cytosol viscosity. Relaxation is highly heterogeneous across the RBC population, yet the three relaxation times are correlated, showing dynamical scaling. Finally, we find that glucose depletion and laser illumination of RBCs lead to faster triple exponential kinetics and RBC rigidification. Viscoelastic phenotyping is a promising dynamical biomarker applicable to other cell types and active systems. SIGNIFICANCE This research shows the structured viscoelastic dynamics of red blood cells (RBCs) and highlights the significance of considering multiple timescales for understanding their mechanical behavior. The observed triple exponential relaxation behavior, coupled with the proposed viscoelastic model, provides valuable insights into the underlying processes governing RBC mechanics. Furthermore, our findings regarding the impact of glucose depletion and light illumination on RBC rigidity show how environmental factors affect RBC properties. Our results expand the current knowledge of RBC mechanics and pave the way for future investigations of relaxational phenomena in other cell types.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Cell- och molekylärbiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Cell and Molecular Biology (hsv//eng)

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