Spider silk, with its impressive hierarchical structure, is a fascinating material that nature has developed over nearly 400 million years. Furthermore, spider silk can be used for a range of potential medical applications. Specifically, spider silk exhibits promise as a constituent of nerve conduits and a material for nerve regeneration. Silk provides support for the adhesion and movement of Schwann cells (SCs), which are critical for peripheral nerve regeneration [1]. Our recent findings show that even small variations in silk properties affect SCs. For instance, various silk sterilisation procedures have shown significant impact on the motility of SCs along the major-ampullate (MA) silk obtained from Trichonephila edulis spider. Autoclaving has been observed to impede SC movement along the fibre, whereas ethanol treatment increases their speed. These observations may be related to stiffness modification, mainly in autoclaved fibres, and ultrastructural changes in ethanol and autoclaved fibres, as concluded from previous nanobeam X-ray diffraction experiments at ESRF, ID 13 [2]. It is established that SCs demonstrate mechanosensitive behaviour [3,4]. Since they appear to be sensitive to small changes in structure as well, our study focused on analysing strain-dependent ultrastructural changes by conducting x-ray nanobeam experiments at MAX IV, Nanomax. We utilized Tubuliform (TU) and MA silk, which coexist in the protective layer that safeguards Trichonephila inaurata (T. inaurata) spider's eggs. Both types of silk were used to investigate strain-dependent ultrastructural changes. Previous nanobeam X-ray diffraction measurements at ESRF, ID13 showed that β-sheet poly-(L-) alanine nanocrystals for TU silk had a larger d-spacing in intersheet direction compared to MA silk (Fig. 1). These differences in ultrastructure may also be connected to findings from single fiber tensile tests, which indicated that TU silk had lower strength and higher extensibility than MA silk. To study spider silk in a close-to-natural environment, a series of in-situ tensile humidity cell experiments were performed at ESRF, ID 13. Experiments were conducted in varying relative humidities, and nanobeam scanning technology was used to gather position-resolved data on individual spider silk fibers. Initial results show pronounced variations in spider silk ultrastructure as a function of stretching rate and humidity. A more comprehensive set of results will be presented at the conference. 

References

[1] T. Kornfeld et al., Biomaterials, 2021,120692, 271.

[2] A. Naghilou et al., Int. J. Biol. Macromol., 2023, 125398, 244.

[3] G. Rosso et al., Nanomedicine, 2017, 13, 493–501.

[4] Y. Gu et al., Biomaterials, 2012, 33, 6672–6681.