Application of Novel Charge-Imbued Polymeric Membrane towards Protein Purification
- Victor Rodgers, Department Chair, Professor of Bioengineering, University of California, Riverside
- David Jassby, Assistant Professor of Chemical & Environmental Engineering, University of California, Riverside
The incorporation of electrically conductive polymers into ultrafiltration membranes holds the potential to add an additional dimension to current protein separation methodologies, such as those used in isolating target proteins from extraneous proteins in drug production. Here, a novel electrically conductive, poly(vinyl alcohol) carbon nanotube (PVA-CNT) membrane was used to evaluate sieving, hydraulic permeability and biofouling in protein ultrafiltration studies. Specifically, a study was performed using a tangential-flow ultrafiltration device with a 30,000 MWCO membrane, operating pressure of 5 psi, and crossflow shear rate of 194 s-1. Feed solutions of 0.5 g/L bovine serum albumin (BSA, RPI Corp., Mount Prospect, IL) in 50 mM NaCl at pH 7.4 were prepared. Experiments were conducted at different electric potentials applied across the membrane and an opposing carbon-fiber mesh, positioned so that the feed would flow tangentially between them. Retentate and permeate samples were collected at fixed time intervals, and their BSA concentrations were analyzed using HPLC (Beckman-Coulter, Brea, CA) with a BioSep SEC S3000 size exclusion column (Phenomenex, Torrance, CA). The sieving coefficient, the ratio of permeate concentration to retentate concentration, was determined to characterize changes in protein-membrane interactions. The results demonstrated that, due to increased negative applied charge, the observed sieving coefficient for BSA decreased while the permeate flux increased. In the 3.0 V case, where the membrane was treated as the cathode terminal, the average observed sieving coefficient underwent a 97.88% reduction and the average permeate flux increased by 20.63%. However, variance of the applied voltage did not display an impact on membrane hydraulic permeability. This suggests enhanced protein rejection by the PVA-CNT membrane due to coulombic force contributions. Binary protein ultrafiltration studies will be conducted to further understand the protein-membrane interactions, by observing the changes in protein separation efficiency.