Abstract
Protein separation is an integral step in biopharmaceutical manufacture with diffusion-limited packed bed chromatography remaining the default choice for industry. Rapid bind-elute separation using convective mass transfer media offers advantages in productivity by operating at high flowrates. Electrospun nanofibre adsorbents are a non-woven fibre matrix of high surface area and porosity previously investigated as a bioseparation medium. The effects of compression and bed layers, and subsequent heat treatment after electrospinning cellulose acetate nanofibres were investigated using diethylaminoethyl (DEAE) or carboxylate (COO) functionalisations. Transbed pressures were measured and compared by compression load, COO adsorbents were 30%, 70% and 90% higher than DEAE for compressions 1, 5 and 10MPa, respectively, which was attributed to the swelling effect of hydrophilic COO groups. Dynamic binding capacities (DBCs) at 10% breakthrough were measured between 2000 and 12,000CV/h (2s and 0.3s residence times) under normal binding conditions, and DBCs increased with reactant concentration from 4 to 12mgBSA/mL for DEAE and from 10 to 21mglysozyme/mL for COO adsorbents. Comparing capacities of compression loads applied after electrospinning showed that the lowest load tested, 1MPa, yielded the highest DBCs for DEAE and COO adsorbents at 20mgBSA/mL and 27mglysozyme/mL, respectively. At 1MPa, DBCs were the highest for the lowest flowrate tested but stabilised for flowrates above 2000CV/h. For compression loads of 5MPa and 10MPa, adsorbents recorded lower DBCs than 1MPa as a result of nanofibre packing and reduced surface area. Increasing the number of bed layers from 4 to 12 showed decreasing DBCs for both adsorbents. Tensile strengths were recorded to indicate the mechanical robustness of the adsorbent and be related to packing the nanofibre adsorbents in large scale configurations such as pleated cartridges. Compared with an uncompressed adsorbent, compressions of 1, 5 and 10MPa showed increases of 30%, 110% and 110%, respectively, for both functionalisations. The data presented show that capacity and mechanical strength can be balanced through compression after electrospinning and is particular to different functionalisations. This trade-off is critical to the development of nanofibre adsorbents into different packing configurations for application and scale up in bioseparation.
Highlights
The contribution of biotechnology products to the global prescription and over-the-counter pharmaceutical markets were estimated to be worth $118 billion in 2011 with increased focusS.R
In the DEAE and COO nanofibre adsorbents here, the effect of charged groups on the nanofibre strand in solution may lead to ionic repulsion forcing nanofirils apart that make up the strand becoming noticeable
When studying protein separation the highest attainable capacities by functionalisation were found as a repeated treatment of 200 mmol/g adsorbent DAECH for DEAE and 20 mmol/g NaClO for COO adsorbents
Summary
The contribution of biotechnology products to the global prescription and over-the-counter pharmaceutical markets were estimated to be worth $118 billion in 2011 with increased focusS.R. The contribution of biotechnology products to the global prescription and over-the-counter pharmaceutical markets were estimated to be worth $118 billion in 2011 with increased focus. A 1376 (2015) 74–83 including diffusive mass transfer, achievable flow rates and scaleup volumes. Protein bioseparation media using convective mass transfer such as porous membranes and monoliths have received increased attention because they avoid this diffusion limitation and have a higher capture efficiency and reduced buffer use to improve overall productivity [4]. In the last 30 years, rigid porous monoliths have been introduced and developed. The single solid continuous matrix has no interstitial voids and can vastly improve productivity by operating at much higher flowrates than packedbed chromatography [5]. Current advantages in industry have been realised in the polishing stage of monoclonal antibody purification using flowthrough mode where a membrane column binds impurities and allows the target to pass through [6]
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