Hybrid Particle-Nonwoven Membrane Materials for Bioseparations

Abstract

Adsorption separations performed in feed streams containing large particulates pose interesting problems, the solution of which would aid in many fields of bioseapartions. Production of biologically derived protein products is one of the most rapidly expanding sectors in the global economy. The capture and purification of these products has, of late, become the bottleneck of the industry and can account for approximately 50-80% of the production costs. The biopharmaceutical industry has begun to focus on improving overall economics by merging two or more separation schemes into one. The majority of the emphasis has been on combining the initial protein capture and host cell clearance steps; however, many of the currently available methods have shown little efficacy at large-scale. Additionally, interest in the clearance of pathogenic activity, most importantly infectious prions, from blood and blood derived products has grown over the past decade with the increased threat of blood-transfusion of variant Creutzfeldt-Jakob disease. This work characterizes the transport and binding properties of a novel hybrid particle-nonwoven membrane medium in which a polymeric chromatographic resin is entrapped between layers of a nonwoven polypropylene membrane (a particle-impregnated membrane or PIM). This membrane-supported resin construct offers the advantage of increased interstitial pore diameter to allow passage of cells and other debris in the feed, while providing sufficiently high surface area for product capture within the resin particles. Columns packed with stacked disks of PIM displayed excellent flow distribution, and had an interstitial porosity of εb = 0.48 ± 0.01, a 25-60% increase over those typically observed in a packed bed. These columns were able to pass over 95% of E. coli cells and human red blood cell concentrate (RBCC) in 30 column volumes, while maintaining a pressure drop significantly lower than that of a packed bed. The dynamic binding capacity of the chromatographic resin entrapped in the PIM packed column for bovine serum albumin (BSA) was essentially the same as that observed with the same volume of resin in a packed bed. Additionally, the binding of prion was characterized to PIM constructs containing an affinity ligand for PrPSc, in saline, RBCC, and human IgG solutions. The General Rate (GR) model of chromatography was used to analyze experiments indicating that the breakthrough and elution behaviors of the PIM column are predictable, and very similar to those of a normal packed bed. These results indicate that PIM constructs can be designed to process viscous mobile phases containing particulates while retaining the desirable binding characteristics of the embedded chromatographic resin. The PIM systems could find uses in adsorption separation processes from complex feed streams such as whole blood, cell culture, and food processing and could offer a process alternative to expanded beds.