Abstract
Red blood cell (RBC) shape change under static and dynamic shear stress has been a source of interest for at least 50 years. High-speed time-lapse microscopy was used to observe the rate of deformation and relaxation when RBCs are subjected to periodic shear stress and deformation forces as they pass through an obstacle. We show that red blood cells are reversibly deformed and take on characteristic shapes not previously seen in physiological buffers when the maximum shear stress was between 2.2 and 25 Pa (strain rate 2200 to 25,000 s−1). We quantify the rates of RBC deformation and recovery using Kaplan–Meier survival analysis. The time to deformation decreased from 320 to 23 milliseconds with increasing flow rates, but the distance traveled before deformation changed little. Shape recovery, a measure of degree of deformation, takes tens of milliseconds at the lowest flow rates and reached saturation at 2.4 s at a shear stress of 11.2 Pa indicating a maximum degree of deformation was reached. The rates and types of deformation have relevance in red blood cell disorders and in blood cell behavior in microfluidic devices.
Highlights
In contrast to other work, where cells are exposed to a single stress event, our work examines Red blood cell (RBC) in flowing pulsatile shear stress where cells rotate between each stress event
We show that RBCs flowing through deterministic lateral displacement (DLD)-style arrays with a peak stress of 2.2 to 25 Pa (2200 to 25,000 s−1 ), reversibly take on shapes not previously described in studies of shear stress
We observed that at peak shear rates that are comparable to the low physiological range, cells retain their shape throughout the arrays
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It is well known that red blood cells in cylindrical capillaries deform into symmetric and non-axisymmetric parachutes. Beech et al [9] showed red blood cell elongation at constrictions in post arrays at shear stress up to 8400 mPa. The effect of chemical forces on RBC morphology has been the subject of scientific enquiry for longer still. Normal red cells have been observed to reversibly form shapes outside of the SDE sequence through chemical treatments. We show that RBCs flowing through DLD-style arrays with a peak stress of 2.2 to 25 Pa (2200 to 25,000 s−1 ), reversibly take on shapes not previously described in studies of shear stress. Peak shear stress in the array is 5.5 Pa, see Movie S2
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