Valorization of Keratin-Rich Waste: Extraction, Characterization, and Biomedical Applications

Keratin is a fibrous structural protein that occurs in abundance in hair, wool, feathers, horns, and nails, and it is a valuable biopolymer with great biomedical applications. The poultry, textile, and leather industries produce millions of tons of keratin waste annually, resulting in significant environmental problems due to their negligible biodegradability as well as the lack of environmentally friendly disposal methods. Recent studies have moved towards valorizing keratin waste, where ongoing research in extraction, purification, and modification techniques has made its applications viable in wound healing, tissue engineering, drug delivery, cosmetics, and ecological remediation. In contrast to previous reviews, this article presents a critical evaluation of traditional, chemical, and industrial extraction methods, focusing on their efficiency, scalability, and sustainability. This study also emphasizes biomedical applications, addresses the challenges and bottlenecks like immunogenicity, reproducibility, and regulatory hurdles, and charts future research agendas for the development of keratin-based biomaterials within a circular bioeconomy scenario. Thus, this review closes the gap between keratin waste management and biomedical innovation and provides novel insights toward sustainable exploitation and next-generation therapeutic applications.