Silk fibroin from production wastes, a new raw material for biomaterial applications: physicochemical properties and biological performance.

Silk textile production generates considerable amounts of waste, increasing environmental impact. However, this waste holds significant potential as a sustainable source of regenerated silk fibroin (SF) for biomedical applications. This study investigated the physicochemical properties and cellular compatibility of SF extracted from silk cocoons (SFC) and silk waste (SFW). Both materials demonstrated comparable morphology, thermal stability, and wettability. Structural analysis and amino acid composition revealed that while SFC presented a higher molecular weight, lower polydispersity, and a greater presence of charged amino acid residues (Asp, Arg, Lys, and His), the regeneration process effectively compensates for these variations. Specifically, the transition from random coil to β-sheet during film casting homogenizes the matrix, ensuring that the final biological properties remain comparable. Quantitative metabolic assays confirmed that both SFC and SFW maintain cell viability above 70%, meeting ISO 10993-5 standards for non-cytotoxicity. Furthermore, qualitative cell adhesion studies demonstrated effective fibroblast spreading and attachment to both film surfaces, indicating that the initial molecular variations in the waste source do not compromise the resulting matrix's biological performance. These findings highlight that SFW is a functionally equivalent and sustainable alternative to SFC, suitable for the development of advanced biomaterials.