Protein-assisted reductive nanofabrication: silk sericin as a capping-reducing agent in sustainable nanotechnology

Sericin is a water-soluble silk protein, which is currently discarded in silk processing and manufacturing as industrial waste during degumming raw silk. This review critically examines the molecular characteristics of sericin that may contribute to its reducing activity, its proposed roles in nanoparticle formation and stabilization, and the extent to which current mechanistic interpretations are supported by experimental evidence. The performance of sericin is further compared with other classes of bio-reductants, including plant polyphenols, microbial systems, free amino acids, and polysaccharides, with particular emphasis on reduction kinetics, stabilization, reproducibility, and practical applicability. Available evidence indicates that sericin can contribute to both metal-ion reduction and nanoparticle stabilization under appropriate aqueous conditions; however, the relative contributions of individual functional groups and the molecular basis of nanoparticle formation remain incompletely established. Reproducibility is also influenced by variation in sericin composition, molecular characteristics, and preparation conditions. In addition, challenges associated with mechanistic validation, scale-up, formulation stability, and long-term biomedical safety limit assessment of its broader technological applications. Sericin therefore represents a potentially useful biomaterial for sustainable nanofabrication, but further standardized characterization, quantitative mechanistic studies, and scalable process development are required to define its practical advantages more reliably.