Fe-reinforced silkworm silk with superstrong mechanical properties for mass production

Abstract

Silk is a versatile material known for its outstanding properties, including good mechanical performance, luster, and biocompatibility in various fields. However, the growing demand for silk in diverse applications necessitates further improvements in its performance. Traditional methods for improving silk performance face challenges such as low strength, toughness, and limited mass production. Here, we report a novel approach that combines genetic engineering and ion reinforcement to produce silk fibers with exceptional strength and stiffness. By overexpressing iron ion-related protein genes in the anterior silk gland of silkworms, this study successfully increased the iron ion content in the resulting silk. Furthermore, when applied to the large-scale production of hybrid silkworm varieties, the mechanical properties of silk were significantly enhanced, thus facilitating mass production. The resulting silk exhibited remarkable mechanical properties, including a high fracture strength (790.3 MPa), fracture energy (123.2 MJm−3), stretchability (∼21.41 % strain) and Young’s modulus (15.41 GPa). Comprehensive analysis involving dynamic simulation, synchrotron radiation infrared spectroscopy, X-ray diffraction, fluorescence spectroscopy, and circular dichroism analysis confirmed the specific interaction between iron ions and tyrosine within the silk protein. This interaction promoted the formation of increased the β-sheet and crystal contents in the silk fibers, contributing to their improved mechanical properties. Importantly, this concept can be extended to other metal ions, offering a promising method for enhancing silk structure and mechanical properties without changing the silk protein sequence.