Protein adsorption kinetics of mixed-mode adsorbent with benzylamine as functional ligand

Adsorption kinetics of bovine serum albumin (BSA) to mixed-mode adsorbent with benzylamine ligand was studied via stirred-batch uptake experiments. The effects of liquid-phase conditions, such as salt concentration and pH, on the uptake rates of BSA were evaluated by effective pore diffusivity (De)De) derived from the pore diffusion model (PDM). The results indicated that when electrostatic attractive interactions exist between protein and ligand, DeDe increases firstly with increasing salt concentration and then turns to decreasing after reaching the maximum. When there are electrostatic repulsion protein/ligand interactions, it seems that the adsorption process is patch controlled, and the specific salt concentration to result in a minimum adsorption capacity could be found. The value of DeDe showed a similar tendency to the change of adsorption capacities. With the increase of salt concentration, the increase in DeDe value was considered due to the decrease of electrostatic repulsion interactions and increase of hydrophobic interactions between BSA and ligand. Since BSA has the most compact structure at the isoelectric point, which leads to lower hydrodynamic forces, it is reasonable that the maximum of effective diffusion coefficient could be found around the isoelectric point.