Electrostatic Repulsion among Red Blood Cells: Observed by Macromolecule-Induced Cell Aggregation and Flow Behavior of the Cells in Microtubes

Electrostatic repulsive force among human red blood cells (RBCs) was observed by macromolecules-induced RBC aggregation and RBC flow behavior in narrow tube, by reducing the sialic acid content of RBCs with neuraminidase. The electrophoretic mobility of the RBCs was proportional to the sialic acid content. (1) When the sialic acid content was reduced, the RBC aggregation observed with a low shear rheoscope was enhanced with fibrinogen (MW=340,000), Ig G (MW=160,000) or Dextran T-70 (MW=70,400), but did not without the macromolecules. In coexistence of normal cells, sialic acid-reduced cells settled significantly faster, possibly due to their preferential aggregation by the macromolecules. (2) Sialic acid-reduced RBCs accumulated more to flow axis in narrow tube (20-50 μm in inner diameter), especially at acidic pH, as evaluated by the thickness of marginal cell-free layer using an image processor. The thickness was further increased with Dextran T-70 due to the RBC aggregation. Conclusively, electrostatic repulsive force among RBCs provided by sialic acid is important for understanding hemorheological behavior of the RBCs and circulatory disturbances in various diseases.