(729d) Preparation and Characterization of Nonwoven Membranes for Bioseparations

Nonwoven fabrics are of great interest as potential materials for bioseparations due to their controllable porosity, pore size, relatively high surface area and low cost. These materials might have applications in the removal of low concentration contaminants, such as toxins and pathogens, offering the possibility of producing disposable devices, by-passing the validation and cleaning costs associated with these steps. On the other hand, grafted nonwoven materials might also be applicable for the purification of proteins present at high concentration in the feed stream, by producing grafted materials containing a conformal coating of polymer over the base fibers.

Polybutylene terephthalate (PBT) nonwoven membrane was subjected to photo-initiated graft polymerization to achieve a conformal layer of glycidyl methacrylate (GMA). The grafted material was then modified in two ways: (1) by the conversion of the epoxy groups in the polyGMA layer into amino groups, forming an ion-exchange membrane, or (2) by attaching a diethylene glycol (DEG) spacer arm, followed by the attachment of an affinity chromatography ligand, forming an affinity membrane.

The resulting nonwoven membranes were characterized using ATR-FTIR, SEM or XPS, showing that each reaction step was successful, characterizing the chemical functionality and the fiber morphology before and after modification. In order to demonstrate its ability to resist non-specific protein binding, the hydrophylized grafted material with no reactive groups was tested against several proteins, including bovine serum albumin (BSA) and lysozyme for its ability to resist non-specific binding, and showed a reduction of about 1 log in non-specific binding, when compared to the base material.

The ion exchange membrane was tested using BSA, and showed equilibrium binding capacities and dynamic binding capacities of around 170 mg protein/g membrane and 90 mg protein/g membrane, respectively. These values correspond to 80 and 42 mg protein/ml of membrane bed (in column format). A separation of a mixture of human immunoglobulin G (HIgG) and human serum albumin (HSA) yielded fractions with 93.4% purity in hIgG (as a flow-through fraction) and 99% purity in salt-eluted HSA. The results obtained for the ion-exchange membrane suggest that the nonwoven produced has a high capacity for binding of proteins, and is a promising material for use in bioseparations.

The affinity membrane was tested against a contaminant protein typically present at very low concentrations in feed-streams common to the bioprocessing industry. The modified nonwoven membrane was capable of capturing the low-concentration target protein from a complex animal tissue homogenate processed minimally, while binding significantly less of other proteins non-specifically, when compared to a resin containing a similar ligand.  These results show that nonwoven fabrics have the potential to become a viable alternative to resins as a medium for protein purification.