Electro-osmotic studies of endothelial cell surface

The surface properties of human umbilical vein endothelial cells (HUVEC), which form the inner walls of blood vessels, have been studied by electro-osmosis measurements. The data are analyzed on the basis of an electrophoresis theory of ''soft'' particles (that is, particles covered by polyelectrolyte layers). This theory utilizes two parameters, i.e. the density of fixed charges in the cell surface layer and a ''softness'' parameter (1/lambda) which corresponds to the reciprocal of the coefficient of the frictional forces exerted by the surface layer on the liquid flow in the surface layer. It is found that the ''softness'' parameter for HUVEC is very large, i.e. the surface of HUVEC is very soft compared with those of other biological cells such as erythrocytes or human promyelocytic leukemia cell lines (HL-60RG cells) which we have studied before. The obtained value of 1/lambda is comparable to that observed for a poly (NIPAAm) hydrogel layer in a swollen state. The charge density in the surface layer of HUVEC, however, is found to be similar to those for other biological cells.