Analysis of enzyme‐treated red blood cell surface and haemagglutination using a theory of soft particle electrophoresis

Enzymatic treatment of red blood cells is thought to reduce the cell zeta (zeta) potential, effectively decreasing the distance between cells to less than the length of an immunoglobulin G antibody binding site, and resulting in agglutination of cells. However, the zeta potential given by Smoluchowski's formula is based on theories of the electrophoresis of hard colloidal particles. A theory has recently been developed for the electrophoresis of colloidal particles covered with polyelectrolytes, which we call 'soft particles'.The electrophoretic mobility of red blood cell treated with papain and neuraminidase was measured as the electrolyte concentration of the medium using phosphate buffer. The results were analysed via the formula for 'soft particles'. This mobility formula involved two parameters, the fixed charge density (ZN) and parameter 1/lambda characterizing the 'softness' of the cell surface layer.The best-fit curves of 0.1 units neuraminidase-treated red blood cells indicated that ZN decreased by 76% and 1/lambda decreased by 8% compared to intact red blood cells. In contrast, in 5 units of papain-treated red blood cells ZN decreased by 45% and 1/lambda decreased by 33% compared to intact red blood cells.The present study shows that the change in ZN for neuraminidase-treated cells was very large, but the cells did not become agglutinable. Papain-treated cells had changes in both ZN and 1/lambda, and the cells became agglutinable. 1/lambda is one of the important factors for agglutination.