Augmented Mass Transport of Macromolecules in Sheared Suspensions to Surfaces

Abstract

Results are reported on the adsorption of bovine gamma globulin (γG) from aqueous suspensions of red blood cell (RBC) ghosts onto quartz planar surfaces under laminar shear flow conditions. Adsorption was measured continuously and in situ under diffusion-limited transport conditions in a rectangular channel flow system. The effective (i.e., enhanced over Brownian) diffusion coefficients of the protein solutes were evaluated using total internal reflection fluorescence as a function of suspension particle volume fraction (5 to 45%), particle deformability, and wall shear rate (400 to 1,400 s-1). Augmented mass transport of γG (defined as De /Ds - 1, where De and Ds are, respectively, the effective diffusivities in flowing and stationary suspensions) was found to be 120% in 5% ghost suspensions at a shear rate of 400 s-1 and to increase nearly fifty times to 4,500% in 45% ghost suspensions at 1,400 s-1. Regardless of shear rate, γG augmentation in suspensions of hardened ghosts compared to unhardened was about 200% greater for 5% suspensions and decreased to a value of about 100% for 45% suspensions.