Fabrication of electrospun ion exchanger adsorbents with morphologies designed for the separation of proteins and plasmid DNA.

ABSTRACT

Electrospun cellulose adsorbents are an emergent class of materials applied to a variety of bioprocess separations as an analogue to conventional packed bed chromatography. Electrospun adsorbents have proven to be effective as rapid cycling media, enabling high throughput separation of proteins and viral vectors without compromising selectivity and recovery. However, there is a current lack of knowledge in relation to the manipulation and control of electrospun adsorbent structure with function and performance to cater to the separation needs of emerging, diverse biological products. In this study, a series of electrospun cellulose adsorbents were fabricated by adjusting their manufacturing conditions. A range of fiber diameters (400 to 600 nm) was created by changing the electrospinning polymer solution. Additionally, a range of porosities (0.4 to 0.7 v/v) was achieved by varying the laminating pressures on the electrospun sheets. The adsorbents were functionalized with different degrees of quaternary amine ligand density to create 18 prototype anion exchangers. Their morphology was characterized by BET nitrogen adsorption surface area, X-ray computed tomography, capillary flow porometry and scanning electron microscopy measurements. The physical characteristics of the adsorbents were used in an adapted semi-empirical model and compared to measured permeability data. Permeabilities of prototypes ranged from 10-2 to 10-4 mDarcy. The measured data showed good adherence to modelled data with possible improvements in acquiring wet adsorbent characteristics instead of dried material. Finally, the electrospun adsorbents were characterized for their binding capacity of model proteins of different sizes (diameters of 3.5 nm and 8.9 nm) and plasmid DNA. Static binding capacities ranged from 5 mg/ml to 25 mg/ml for the proteins and plasmid DNA and showed <20 % deviation from monolayer coverage based on BET surface area. Therefore, it was concluded that the electrospun adsorbents most likely adsorb monolayers of proteins and plasmid DNA on the surface with minimal steric hindrance.