Augmented Mass Transport of Macromolecules in Sheared Suspensions to Surfaces B. Bovine Serum Albumin

Abstract

The augmented mass transport of plasma protein (bovine serum albumin) in a red blood cell ghost particle suspension to a surface was investigated under diffusion-limited conditions in rectangular flow cell system. The augmentation of mass transport of protein was probably due to the random particle motions. A total internal reflection fluorescence (TIRF) method was used to determine the effective diffusivity of bovine serum albumin (BSA), based on the measurement of its adsorption rate to a surface, as a function of suspended particle volume fraction (0.05–0.7) and shear rate. Effective diffusivity results for BSA in suspensions containing red blood cell ghosts showed an enhancement, i.e., augmentation, over the Brownian diffusivity values measured over corresponding homogeneous solutions. The augmentation of protein was defined as (De/Ds) − 1, whereDeis the effective diffusivity under flow andDsis the diffusivity in a stationary suspension. The augmentation of BSA mass transport in RBC ghost suspension was found to be 14–1440% in 5–70 vol% RBC ghost suspension at shear rates of 200–1000 s−1. The augmentation values reported as a function of particle Peclet number (Pe) were in good agreement with literature values. The normalized augmentation (A/Pe) increased with particle volume fraction until it reached a maximum at 45% RBC ghosts, whereby it decreased as the particle volume fraction was further increased. Volume fractions of up to 70% RBC ghosts were studied.