Silk fibroin lipopeptides: Mechanochemical synthesis and physicochemical characterization

This work presents a complete approach, from biomass extraction to the production of surfactant molecules using a new methodology, followed by their characterization. Fibroin was isolated from silk cocoons and enzymatically hydrolyzed to generate low-molecular-weight peptides. Then, silk fibroin-derived amphiphilic lipopeptides with variable hydrophobic chain lengths were produced by a novel mechanochemical eco-friendly approach, without the use of chlorinated agents, as an alternative to the conventional Schotten-Baumann reaction. These molecules were investigated in detail for their equilibrium and dynamic adsorption behavior, self-assembling, zeta-potential, emulsifying, foaming and wetting properties, and compared to model synthetic surfactants. The results showed that fibroin lipopeptides can efficiently reduce air/water surface tension and oil/water interfacial tension. The aggregates of lipopeptides were formed from 0.5 to 2 g.L −1 and showed average diameters between 167 and 224 nm depending on the molecule structure. Fibroin peptides demonstrated valuable physicochemical properties comparable to or better than commercial surfactants. They display excellent emulsifying properties, can form a stable and uniform foam, and ensure good wetting performance. These bio-based amphiphilic molecules can be considered as promising potential candidates for replacement of partially or fully petrochemical-derived surfactants in cosmetics, toiletries and pharmaceutical products. • Silk protein is a biopolymer with low carbon footprint and diverse applications. • Silk fibroin lipopeptides are synthesized by new mechanochemical approach. • Fibroin lipopeptides show good surface activity, emulsifying and foaming capacities. • Analysis of functional properties confirms their strong potential for applications.