Upcycling waste hair and feathers derived keratin into intact cortical cell-derived micro-units via periodate oxidation: Applications & life cycle assessment

With increasing interest in keratin-based biomaterials, such as cortical cell-derived micro-units have gained significant attention for their countless thermo-mechanical strengths with stable biochemical characteristics. However, traditional keratin extraction methods often compromise the integrity of protein structures, which ultimately demolish their broader applications. In this study, we developed a novel periodate oxidation routine for extracting keratin's nano-micro structures from waste hair and feather feedstocks, specifically targeting cortical cell-derived micro-units surface stability. Results showed that periodate oxidation delaminated the fibers into precise spindle-shaped cortical cell-derived micro-units with an average length of 40-80 μm and width of 5-8 μm. The extraction yields were 31.28 wt% for hair-derived and 20.64 wt% for feather-derived micro-units. These micro-units, together with keratin-derived fragments generated during emulsification, effectively stabilized oil-in-water emulsions and inhibited droplet aggregation. Additionally, we performed a life cycle assessment to evaluate the environmental impact of the keratin-emulsion production process. Overall, this work demonstrates that periodate oxidation enables the selective recovery of keratin cortical micro-units from waste hair and feathers, providing a sustainable route toward high-quality keratin-based biomaterials for industrial applications.