Hierarchically structured ultrathin sodium alginate/ethylene-vinyl alcohol copolymer composite nanofiber membranes for precision filtration and concentration of bio-nanoparticles

The concentration and purification of bio-nanoparticles, including viral vectors and exosomes, remain challenging because membrane-based bioprocessing must simultaneously provide high permeability, effective particle retention, low nonspecific fouling, and robust stability under process-relevant conditions. Here, we report a scalable sodium alginate (SA)/ethylene-vinyl alcohol copolymer (EVOH) nanofibrous membrane designed for bio-nanoparticles processing. The membrane was fabricated through isopropanol-induced self-assembly followed by covalent-ionic dual crosslinking, producing a highly interconnected dual-nanofiber network with an ultrathin selective layer, tunable pore structure, and enhanced aqueous stability. The resulting membrane exhibited enhanced hydrophilicity, robust mechanical integrity, and favorable separation characteristics for nanoscale bioparticle fractionation. Using 25 nm colloidal gold nanoparticles as a model, the membrane demonstrated an improved balance between water permeability and particle rejection. Its practical separation capability was further validated by tangential flow filtration (TFF) of 50 nm polystyrene nanoparticles and PP7 bacteriophage, enabling efficient concentration with high viral retention, with a log reduction value exceeding 7. Importantly, the fabrication strategy was successfully translated to pilot-scale production, demonstrating its potential for large-area deployment. Overall, this work provides a scalable membrane platform that alleviates the conventional permeability-selectivity compromise and offers a promising route for bio-nanoparticles concentration and purification in biopharmaceutical downstream processing.