Mechanical Testing of Engineered Spider Silk Filaments Provides Insights into Molecular Features on a Mesoscale

Abstract

Spider dragline silk shows the highest toughness in comparison to all other known natural or man-made fibers. Despite a broad experimental foundation concerning the macroscopic silk thread properties as well as a thorough simulation-based molecular understanding, the impact of the mesoscale building blocks, namely nano-/submicrometer-sized filaments, on the mechanical properties of the threads remains the missing link. Here, we illustrate the function of these mesoscaled building blocks using electrospun fibers made of a recombinant spider silk protein and show the impact of β-sheet content and fiber hydration on their mechanical performance. Specifically elucidating the interplay between β-sheet-cross-linking (fiber strength) and structural water (fiber extensibility), the results bridge the gap between the molecular and the macroscopic view on the mechanics of spider silk. It is demonstrated that the extensibility of the here used single (MaSp2-like) protein system is in good accordance with the simulated extensibilities published by other groups. Furthermore, sufficient hydration of the fibers is shown to be a prerequisite to obtain a toughness in the range of that of natural dragline silk. Preliminary studies on electrospun fibers of the MaSp2-based recombinant spider silk proteins used in this work have indicated their basic applicability in the technical field of filter systems as well as in regenerative medicine. The presented work provides a fundamental understanding of the mechanical performance of such fibers under different wetting conditions, a prerequisite to further specify their potential for such applications.

Effects of Osiris9a on Silk Properties in Bombyx mori Determined by Transgenic Overexpression

“…The amide I band at 1580-1720 cm −1 was used for a peak deconvolution analysis ( Figure 5A). According to previous reports, the deconvolution peak in the wave number range of 1615-1645 cm −1 and 1690-1700 cm −1 represent β-sheet structure, 1645-1665 cm −1 represents α-helix/random coils structure, 1680-1690 cm −1 represents β-turn structure [24][25][26][27][28][29]. The composition of secondary structures of the silk fibers differed between the transgenic and wild-type lines ( Figure 5A).…”

Silk nanofibril self‐assembly versus electrospinning

“…By contrast, state of the art electrospinning does not involve such complexity and it relies rather on the fiber formation during a quick solvent evaporation and jet solidification. Such high-speed fiber formation does not allow silk proteins to self-assemble into highly organized structures.. Consequently, proteins are "frozen" in a randomly oriented pre-assembled state, and the formation of stable β-sheet crystals must usually be subsequently induced by post-treatment of the solid fiber impairing native ordering of the structural elements (Amiraliyan et al, 2010;Jeong et al, 2006;Lang, Neugirg, et al, 2017;Leal-Egana et al, 2012;Machado et al, 2013). This hypothesis is supported by experiments that showed the dependency of silk protein assembly on the drying times of the silk solution (Zhang, Zuo, et al, 2012).…”

“…Thus, in contrast to self-assembled fibrils revealing defined lengths from hundreds to few thousand nanometers, the electrospinning processing allow for production of endless nano-fibers which, depending on the technical setup, end up in distinct morphologies. Thus, the fibers can be randomly oriented into nonwoven meshes or aligned into ordered fiber bundles and yarns (Lang, Neugirg, et al, 2017;Meinel et al, 2009;Peng et al, 2016). Further, advanced composite materials with complex structures such as side-by-side (Peng et al, 2016) or core-shell arrangements (Zhu et al, 2016) for advanced functionality and 3D scaffolds (Lee et al, 2014;Sheikh et al, 2015;Yang et al, 2015) are possible.…”

“…(Machado et al, 2013;Ner et al, 2009;Ohgo, Zhao, Kobayashi, et al, 2003;Qiu et al, 2010;Zhu et al, 2016), oriented fiber mats (Zhu et al, 2015) and fiber bundles (Lang, Neugirg, Kluge, Fery, & Scheibel, 2017). Lang, Neugirg, et al (2017) performed (nano-)mechanical measurements based on lateral force microscopy (LFM) to identify the deformation behavior of single electrospun eADF4 fibers. They demonstrated that posttreatment (crystallinity) and hydration remarkably increased the fibers' toughness up to a level of the natural fiber (152 AE 36 MJ/m 3 ).…”

Новые Перспективные Материалы На Основе Рекомбинантного И Регенерированного Шелка Для Медицины И Конструкционных Тканей

“…Вследствие различных закономерностей формирования структуры волокон в процессе мокрого формования и электроформования и отсутствия ориентационной вытяжки нановолокнистых материалов видно, что нано-и микроволокна на основе рекомбинантного спидроина с одинаковым содержанием β-листов обладают разными механическими свойствами (табл. 8) [14,52].…”