Keratin 3D Printing: Sustainable Biomaterials for Regenerative Medicine and Biomanufacturing

Keratin as an abundantly available natural protein from sources such as hair, wool, and feathers possesses excellent biocompatibility, biodegradability, and bioactivity that support cell growth. Recent advances in extracting, purifying, and characterizing keratin have led to the development of various keratin-based biomaterials, such as fibers, gels, films, and nanoparticles via conventional fabrication methods. However, these biomaterials are often limited by simple geometries, weak mechanical strength, and limited reproducibility. Emerging 3D printing technologies offer a promising alternative, allowing the creation of keratin-based scaffolds with precise architecture, tunable mechanical strength, and reproducible geometries. Despite keratin's abundance and biological advantages, the use of keratin in 3D printing remains relatively underexplored. This review provides a comprehensive overview of keratin's molecular structure and biochemistry, its diverse natural sources, extraction and purification methodologies, and the cross-linking mechanisms (chemical, UV, and enzymatic) used to formulate printable keratin-based inks. Furthermore, it discusses the biomedical applications of keratin-derived bioinks in tissue engineering and additive biomanufacturing, with emphasis on skin and bone regeneration. Combining keratin's biological functionality with the design flexibility of 3D printing offers a sustainable and cost-effective pathway toward next-generation biomaterials for regenerative medicine.