Keratinous Human Hair as a Precursor for Functionalized Carbon: Influence of Pyrolysis Temperature on Structure and Biomedical Performance.

Carbon is a fundamental element that possesses remarkable engineering versatility due to its unique capacity for diverse solid-state bonding. While carbonaceous matrices hold immense biomedical potential, optimizing their thermal conversion pipelines is mandatory to ensure the complete elimination of raw biological contaminants while preserving material integrity. Among various proteinaceous biomass streams, human hair represents an abundant, globally ubiquitous waste resource that has emerged as a high-potential precursor for engineered functional carbon platforms. Compared to conventional plant-derived or petrochemical alternatives, human hair-derived carbon (HHC) features a unique macromolecular architecture that enables the intrinsic self-doping of biogenic nitrogen (N) and sulfur (S) heteroatoms into the emerging graphitic lattice, yielding an optimal electroactive microenvironment for stem cell manufacturing and tissue engineering. This review comprehensively scrutinizes how thermal processing windows (400 °C-900 °C) systematically transform the raw proteinaceous matrix into a highly crystalline, conductive carbon framework, fundamentally modulating its mechanical modulus, charge-transfer resistance (R ct), and microporous volumes. Furthermore, we analyze donor-dependent macromolecular variabilityincluding ethnicity, age, and historical cosmetic exposureand detail the targeted pretreatment chelation protocols required to ensure batch reproducibility and clinical-grade purity. By providing a deep mechanistic understanding of the thermal processing of HHC, this work advances the high-value valorization of municipal biomass waste within the circular bioeconomy paradigm, mitigating environmental liabilities while accelerating sustainable, electro-inductive biomedical applications.