(306a) Exploration of Dual-Layer Sulfonated Polyethersulfone/polyethersulfone Hollow Fiber Membranes in Protein Separation

Proteomics is the large-scale study of proteins - the ultimate products of genes. By understanding proteins, researchers hope to understand the biochemical mechanisms of disease, leading to the development of drugs with an improved safety profile and a greater probability of clinical trial success. To gain a comprehensive understanding of protein function and regulation, researchers must separate proteins, then identify and characterize the expressed proteins. Unfortunately, the protein separation is a difficult process due to the complexity of proteins selves and their biological environments. The proteins are composed of numerous amino acids and the sequence of amino acids in each protein is unique to that protein; therefore, each protein has its own particular 3-D shape or native conformation. An amino acid is electrically neutral at its isoelectric point (pI) and has a positive or negative charge at lower or higher pH, respectively. To obtain a completely purified protein, many separation processes have been developed based on different protein properties, and they include chromatography, electrodialysis, electrophoresis, membrane chromatography and ultrafiltration (UF). Among them, the membrane-based protein separation processes may be potentially attractive ones.

The sulfonated polyethersulfone (SPES) material with a negative charge was applied to separate a bovine serum albumin (BSA) and hemoglobin (Hb) mixture through a electrostatic interaction mechanism in this work because these two proteins possess the very similar molecular sizes (66kDa vs. 65kDa) but different pI values (4.8 vs. 6.8). The dual-layer hollow fiber configuration was utilized in this work because SPES materials with a high degree of sulfonation (DS) (i.e. a high charge density) become highly hydrophilic and are normally difficult to precipitate and solidify in water and other common non-solvents, such as methanol, ethanol and isopropanol. Through continuous endeavor in developing the co-extrusion technology, the delamination-free dual-layer hollow fiber membranes consisting of a selective SPES outer layer and a porous supporting PES inner layer were successfully fabricated. These newly developed dual-layer SPES/PES hollow fiber membranes exhibit the best and most durable protein separation performance among all spun fibers in this work. They have a BSA/Hb separation factor of above 10 and last for almost 1 day, which is very attractive for practical applications of membrane technology in protein separation because the membrane separation performance normally decreases rapidly with a function of time induced by some reasons such as fouling and saturation of binding sites.