Transition metal ion-catalyzed assembly of oat peptides into amyloid fibrils: Feasibility, physicochemical properties, and chitosan film reinforcement

Currently, the preparation of protein-based amyloid fibrils (AFs) is challenging due to long heating times and high energy consumption, hindering large-scale application. However, this study found that transition metal ions (Zn²⁺ and Fe²⁺) can rapidly induce AF formation from oat peptides (3 kDa < Mw < 10 kDa), reducing acid-heat treatment time by 50–60 %. FTIR analysis revealed that metal ion-induced salt bridges and peptide-peptide hydrogen bonds increase the β-sheet content necessary for AF formation to 14–23 %. Physicochemical analysis showed that peptide-based AFs have strong cross-linking ability and high hydrophobicity (270–293), but low solubility (22.3–34.7 %). When cross-linked in chitosan films, AFs form a network structure, resulting in composite films with high mechanical properties (10.8–11.6 mPa), extended ductility (137–142 %), and notable resistance to swelling (18.7–18.8 %) and water solubility (21.5–21.6 %). This significantly improves the common shortcomings of natural degradable films and highlights their potential for application. The research deepens our understanding of the interaction between transition metal ions and peptides, providing a technical foundation for the large-scale preparation and application of peptide-based AFs.