A versatile fabrication route for screening block copolymer membranes for bioprocessing

Traditional polyethersulfone (PES) filters, widely used for sterile, viral and ultrafil- tration often exhibit limited selectivity-permeability due to the heterogenous pore size distribution. Such limitations have sparked interest in developing novel isoporous mem- brane materials and fabrication techniques to overcome the selectivity-permeability upper bound. Among several promising candidates, block copolymer membranes pro- duced via the self-assembly and non-solvent induced phase separation (SNIPS) method offer distinct advantages, such as customisable pore size, narrow dispersity, high poros- ity and mechanical flexibility. However, achieving the desired structure formation in SNIPS remains a complex optimisation procedure, rendering this approach unsuitable for the rapid screening of new block copolymer candidates. This study explores a direct spin coating method to fabricate a poly(styrene)-block- poly(methyl methacrylate) (PS-b-PMMA) thin film composite membrane, integrating a block copolymer layer with rigid anodic aluminium oxide (AAO) support. The pro- cess involves depositing the polymer solution onto a water-filled AAO substrate via spin coating. Compared with the SNIPS method, this fabrication process greatly re- duces the complexity of optimisation to yield an isoporous membrane structure for filtration purposes. We present this approach as a straightforward and reliable plat- form method for the rapid screening and evaluation of block copolymer membranes in their initial development stages. When compared to commercial PES membranes with similar molecular weight cut-offs, these novel PS-b-PMMA thin film composite membranes showed similar transmission rates for Bovine Serum Albumin and a Mon- oclonal Antibody while providing a 9 fold enhancement in Thyroglobulin rejection. This indicates a superior performance in terms of cut-off precision. The membranes demonstrate potential for the removal of viruses and antibody aggregates in the down- stream processing of monoclonal antibody production, which could reduce the burden of chromatographic polishing steps. An advance which offers promise for improving efficiency and reducing costs in biopharmaceutical manufacturing.