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Engineered spider silk proteins for biomimetic spinning of fibres with a toughness equal to silk from spiders

Researchers at Karolinska Institutet and SLU have managed to do what nature itself cannot. By using insights of basic biological principles and protein engineering, they have managed to increase the artificial silk fibres’ mechanical properties, which resulted in fibres with increased tensile strength and two fibre types displaying toughness equal to native spider silks and a yield in line with the requirements for an economically viable industrial bulk scale production.


The research team spun a bundle of artificial silk fibre. Image credit: Marlene Andersson / Karolinska Institutet

Spider silk is the most rigid fibre in nature, and bulk production of artificial spider silk that matches its mechanical properties remains elusive. The development of miniature spider silk proteins (mini-spidroins) has made large-scale fibre production economically feasible, but these fibres’ mechanical properties are inferior to native silk.

Researchers at Karolinska Institutet and SLU have done what nature cannot do by using insights into fundamental biological principles and protein engineering to increase the artificial silk fibres’ mechanical properties.

These results are presented in a new paper by Anna Rising, senior researcher at the Department of Biosciences and Nutrition, Karolinska Institutet and Professor at SLU, and her group.

Overcoming biological laws
The spider silk fibre’s tensile strength is conferred by protein segments that are tightly packed and zipped together. Spider silk proteins are secreted from the silk gland cells, so they must be void of long stretches of hydrophobic residues since such segments get stuck in membranes inside the cell. At the same time, such hydrophobic residues can mediate tighter interactions in the protein zippers, attractive features for the generation of artificial solid silks.

Protein production in bacteria can circumvent natural laws that spiders must obey since they lack the membranes to trap the cells’ proteins. Building on these insights, the researchers designed spider silk proteins predicted to form more robust zippers and successfully produced a panel of these in bacteria.

The biomimetic spinning of these engineered spider silk proteins resulted in fibres with increased tensile strength, and two fibre types displayed toughness equal to native dragline silks. Bioreactor expression and purification resulted in a protein yield of ~9 g/L, in line with the requirements for an economically viable industrial bulk scale production. The researchers’ proteins from the 1L bacterial culture would be enough to spin an 18 km long fibre.

Source: Karolinska Institutet

https://www.technology.org/2022/04/07/engineer-spider-silk-protein-fibres/