Impact of keratin subfractions on the ultrafine particles filtration of sustainable electrospun human hair keratin/PVA nanofibers.

Ultrafine particulate matter, especially particles below 100 nm, poses severe health risks due to their deep penetration into pulmonary regions and systemic circulation, emphasizing the need for sustainable and effective air filtration technologies. Conventional air filtration systems often face limitations in capturing these particles efficiently while maintaining low airflow resistance. A suggested solution lies in the use of bimodal nanofiber architectures, which combine coarse and fine fiber populations to enhance particle capture while preserving breathability. In this study, we proposed to develop electrospun nanofiber air filters using keratin extracted from human hair and blended with polyvinyl alcohol (PVA). By varying the ratios of Keratin-Associated Proteins (KAPs) and Keratin Intermediate Filaments (KIFs), we investigated how their distinct amino acid compositions and electrostatic properties influence fiber morphology, mechanical performance, and filtration efficiency. KAPs, rich in negatively charged and thiol-containing residues, enhanced ultrafine particle capture through electrostatic interactions and Brownian diffusion. KIFs, dominated by hydrophobic and structural amino acids, reinforced fiber rigidity and promoted size-based filtration via interception and inertial impaction. Filters fabricated with 10/0 (pure KAPs) and 3/7 KAPs/KIFs ratios exhibited the highest Quality Factor (QF), balancing low-pressure drop with effective nanoparticle removal. This performance was attributed to synergistic effects from enhanced surface charge, optimized fiber packing, and the slip effect facilitated by bimodal fiber diameters. These results establish keratin subfraction engineering as a potential strategy for designing sustainable, high-performance air filtration materials targeting ultrafine particulate pollution.