9Viral vectors used in emerging gene therapies face challenges of significant yield loss during 10 downstream processing primarily due to their large size, fragility and mass transfer limitations of the 11 traditional porous chromatography adsorbents. The large size of the vectors in relation to key 12 impurities makes them suitable solutes for ultrafiltration-based separations. Efforts to utilise 13 ultrafiltration for virus purification are often restricted to commercial polymeric membranes with wide 14 pore size distributions and tortuous, interconnected channels. Membranes with narrow pore 15 distributions and straight pore channels such as porous anodic alumina (PAA) may present 16 opportunities for improved virus purification. This paper examines the use of porous anodic alumina 17 membranes for application in virus separation by using model solutes such as thyroglobulin and 18 protein nanoparticles. A systematic approach is used to select a polymeric ultrafiltration membrane 19 rating for comparison with 20nm rated PAA membrane by comparing hydraulic permeability and 20 dextran sieving characteristics of the membranes. Differences in the filterability of the model solutes 21 were characterised. Finally, a discontinuous diafiltration experiment was employed to fractionate 22 smaller model impurity and protein nanoparticles. Results indicate that PAA membranes have 23 superior fouling resistance with 3-4 folds higher flux recovery ratio and 3-fold higher purification 24 factors compared to the polymeric membranes, but the presence of surface defects make them more 25 susceptible to product loss through leaky transmission. 26 explore the use of ultrafiltration based processing instead of chromatography based processes by exploiting differences in the size of impurities and viral particles [6][7][8][9]. Most of the reported literature 35 compares different molecular weight rating or pore size ratings of polymeric ultrafiltration membranes 36 or different modules such as hollow fibre and cassette [6, 8]. These membranes have wide pore size 37 distribution, which is often reported to affect the membrane performance especially retention of large 38 biomolecules such as viruses [10, 11]. Isoporous membranes with different porous architectures such 39 as porous anodic alumina (PAA) membranes are however being investigated in other fields such as 40 nanofiltration for water purification and biosensors.
41Porous anodic alumina membranes are widely studied for applications in label-free biosensors [12][13][14] 42 for use as point-of-care diagnostic devices. Applications of PAA membranes in bioseparations have 43 been limited to diffusion based separations for haemodialysis [15], separation of similarly sized 44 proteins by exploiting differences in solute charge [16], enriching phosphoproteins for mass 45 spectrometry [17] and ultrafiltration of small proteins [18-20]. A few reports on PAA membranes have 46 examined their potential for virus separations. Moon et al., [21] reported the ability of 35-nm pores of a 47 PA...
