Electrophoretic mobility of human erythrocytes in the presence of poly(styrene sulfonate).

Abstract

The adsorption and depletion of the anionic polymer poly(styrene sulfonate) (PSS) on fresh human red blood cells (RBC) were investigated by measuring RBC electrophoretic mobility as a function of polymer molecular mass (48-2610 kDa), ionic strength (15 and 150 mM NaCl) and polymer concentration (<or= 1.5 g/dL). A subset of studies was carried out using fixed and PSS-coated cells. Our results indicate a marked increase of mobility with molecular mass and polymer concentration. Adsorption of PSS onto fresh RBC was weak, with normal mobility restored following washing cells in PSS-free buffer. Calculated zeta potentials based upon mobility and medium viscosity rose up to 618 mV for 2610 kDa PSS compared to 13 mV for control cells, thus suggesting significant polymer depletion at the cell surface; fixed and PSS-coated RBC were insensitive to medium viscosity, also validating this depletion layer hypothesis. Calculated values of increased RBC surface charge were used to estimate polymer adsorption per cell; these estimates indicated linear adsorption isotherms and binding levels consistent with studies employing neutral polymers. In overview, our results suggest the usefulness of microelectrophoresis methods for studies of RBC interactions with charged polymers or proteins, and the value of this approach for future studies using proteins known to affect RBC-RBC interactions.