Correlating the secondary protein structure of natural spider silk with its guiding properties for Schwann cells

• Published in: Materials Science & Engineering C 2020-11, Vol.116, p.111219-111219, Article 111219
• Main Authors: Naghilou, Aida, Pöttschacher, Lena, Millesi, Flavia, Mann, Anda, Supper, Paul, Semmler, Lorenz, Weiss, Tamara, Backus, Ellen H.G., Radtke, Christine
• Format: Article
• Language: English
• Subjects: Animals; Aqueous environments; Autografts; Avicularia avicularia; Biomaterials; Cocoons; Conduits; Fibers; Fibrous materials; Hydrogels; Material properties; Materials science; Morphology; Nephila edulis; Nerve guidance conduit; Nerve regeneration; Nerve Tissue; Peripheral nerve reconstruction; Peripheral nerves; Protein structure; Protein Structure, Secondary; Proteins; Raman spectroscopy; Scanning electron microscopy; Schwann Cells; Sheets; Silk; Spiders; Stiffness; Tissue Engineering; Transplantation
• ISSN: 0928-4931; 1873-0191
• DOI: 10.1016/j.msec.2020.111219

The successful reconstruction of supercritical peripheral nerve injuries remains a major challenge in modern medicine. Progress in tissue engineering has enabled the development of nerve guidance conduits as an alternative to autologous nerve transplantation and the enrichment of conduits with fibrous materials or hydrogels has shown great potential in bridging nerve defects. The application of the dragline silk of spider genus Nephila as a filament for nerve guidance conduits has led to promising results. However, the use of spider silk has been phenomenological so far and the reasons for its success are still not identified. This renders a targeted tuning of synthetic fibrous luminal fillings such as recombinant silk out of reach. In this work the existing research was extended and in addition to dragline, the cocoon silk of Nephila edulis, as well as the connecting and attaching silk of Avicularia avicularia were investigated. Scanning electron microscopy revealed a difference in size and morphology of the spider silks. However, in vitro experiments indicated that Schwann cells adhere to the four fibers, independent of these two attributes. Raman spectroscopy in native state and aqueous environment demonstrated similar secondary protein structures for dragline, cocoon, and connecting silk. In contrast, the attaching silk showed a significant lower conformation of β-sheets, crucial for the stiffness of the silk. This was in line with the in vitro experiments, where the flexible attaching silk fibers adhered to each other when placed in liquid. This resulted in their inability to guide Schwann cells, leading to the generation of cell agglomerations. This direct comparison demonstrated the crucial role of β-sheets conformation for the guidance properties of natural spider silk, providing essential insights into the necessary material properties for the integration of fibrous luminal fillings in nerve guidance conduits. [Display omitted] •The diameter and the morphology of spider silk does not affect the adhesion of rat Schwann cells•Secondary protein structure of connecting silk from A. avicularia is similar to dragline and cocoon silk from N. edulis•The attaching silk of A. avicularia has a smaller β-sheets conformation•The β-sheets are crucial for the guiding properties of natural spider silk