Quantitation of surface affinities of red blood cells in dextran solutions and plasma

Mutual affinities of red blood cell surfaces in dextran solutions and plasma have been determined experimentally. The approach was to use dual micropipet techniques to manipulate cells and spherical cell "fragments" into position for contact. After contact, the red cells encapsulated the fragments to an extent that depended on the affinity. Surface affinity is defined as the reduction in free energy per unit area of interface that is associated with formation of adhesive contact. The surface affinity was calculated with the use of a minimum free energy analysis and knowledge of the red cell membrane elastic properties. With this approach, surface affinities were measured for normal and neuraminidase-treated red cells in plasma and various solutions of dextran. The data presented are the first direct measurements of the affinity of a biological membrane for another surface in a well-defined system. The peak surface affinities of normal red blood cells were found to be 4.9 x 10(-3) erg/cm2 in D70, 2.2 x 10(-2) erg/cm2 in D-150, and 2.0 x 10(-3) erg/cm2 in plasma. Neuraminidase-treated cells had higher affinities than normal cells: at least 2.8 x 10(-2) erg/cm2 in D70 and 1.8 x 10(-3) erg/cm2 in D28, which does not aggregate normal red cells.