The isolation and purification of biotherapeutic protein products from genetically engineered cell culture or from human plasma contributes anywhere from 50 to 80% of the cost of these drugs. One of the major challenges of the industry is to reduce operating separation costs by minimizing the number of purification steps. One approach to this is the use of affinity adsorption methods to recognize the desired protein product. The other is to do a preliminary isolation or concentration step early in the process, even in the presence of whole cells from the cell culture medium.

In this project, we are investigating the use of small, robust and inexpensive peptide affinity ligands attached to nonwoven fabrics to effect the separation. This might provide an attractive alternative to traditional chromatographic resin columns or porous membranes. The advantages of this nonwoven separation system are the low cost, negligible diffusional limitations, low pressure drop and the controllable pore size and fiber diameter which makes it possible to pass complex media such as a homogenized cell culture medium through the fabric matrix. A commercially available PBT nonwoven fabric was used to create a new affinity membrane in this study. Hydroxylated polyacrylates were grafted onto the nonwoven surface, together with a spacer arm to decrease nonspecific binding and to allow for convenient ligand coupling. The physical and chemical properties of this modified material were studied by SEM, FTIR, XPS and EA (elemental analysis). A conformal hydrophilic layer around each fiber was achieved by optimizing the surface treatment process. The results of preliminary studies on the removal of prion protein from red blood cell concentrate and plasma, as well as the removal of viruses from plasma samples will be presented.