The single erythrocyte rigidometer (SER) as a reference for RBC deformability

Area of Science:

• Biophysics
• Hematology
• Cellular Mechanics

Background:

• Red blood cell (RBC) deformability is crucial for microcirculation.
• Quantifying RBC deformability is essential for understanding various hematological conditions.
• Existing methods for measuring RBC deformability yield varied results.

Purpose of the Study:

• To evaluate the influence of cytoplasmic viscosity, membrane viscoelastic properties, and area-to-volume ratio on RBC deformability.
• To assess the performance of a novel pore-based system (SER) for quantifying RBC deformability.
• To compare the results obtained from the SER with other established RBC deformability measurement techniques.

Main Methods:

• Red blood cells were subjected to chemical alterations (acetylphenylhydrazine, diamide) and osmotic stress (swelling, shrinking) to modify their physical properties.
• The Shear-induced Erythrocyte Rheometer (SER) was used to measure the passage time of individual RBCs through a defined pore (5.8 µm diameter, 50 µm length) under controlled shear stresses (1.5-4 Pa).
• RBCs were also tested using a filtrometer, packed cell viscometry, rheoscope, and ektacytometry for comparative analysis.

Main Results:

• The passage time of RBCs through the SER pore was primarily influenced by changes in cytoplasmic viscosity.
• Alterations in membrane viscoelastic properties and the area-to-volume relationship showed a secondary impact on passage time.
• Significant discrepancies were observed when comparing the deformability measurements from the SER with the other four techniques.

Conclusions:

• The SER system effectively quantifies RBC deformability, with cytoplasmic viscosity being the dominant determinant.
• The SER offers a distinct perspective on RBC deformability compared to other commonly used methods.
• Further investigation is warranted to understand the differences in RBC deformability measurements across various techniques.