Nanohybrid Fibers via Direct Nanoparticle Injection into the Spider's Silk Gland

Spider silk demonstrates an impressive balance of high strength and elasticity, which results from the hierarchical self-assembled structure of spider silk proteins during the fiber biosynthesis and spinning process. Enhancing the mechanical characteristics of spider silk fibers and imparting them with functional properties has garnered considerable attention. This challenge underscores the importance of developing strategies for modifying native spider silk. In this study, we introduce an approach to modify the structure and properties of spider silk fibers by injecting magnetite hydrosols directly into the spiders' silk glands. This results not only in the magnetic functionality of spider silk fibers but also in 82% increase in Young's compared to native spider silk, along with hardness of 1.30 MPa. To explore the nature of this phenomenon, we analyzed the difference in the topography of native Holothele incei spider silk and Fe₃O₄-hybrid spider silk, as well as their corresponding mechanical behavior at the nanoscale. Additionally, we studied the changes in structure, composition, and morphology caused by the inclusion of magnetic nanoparticles. Our findings demonstrate that the polar and hydrophobic interactions between Fe₃O₄ nanoparticles and the amino acid residues in spider silk could influence Young's modulus and hardness of the Fe₃O₄/spider silk hybrid fibers by promoting the protein conformation from an amorphous phase to β-sheets. This can only be achieved when nanomaterials are integrated into the structure within the fiber. The developed approach enables the fabrication of modified spider silk fibers, which can aid in the fundamental study of native spider silk and the development of technologies to fully replicate the properties of native silk in the future. Furthermore, lightweight, flexible, but strong materials are critical in soft robotic applications, where these nanohybrid fibers not only ensure gentle manipulation and reliability, but also their magnetic properties allow for responsive movement and control.