On October 7, Beijing time, in a latest study published in Matter, a research team led by Professor Lin Zhi and Professor Yuan Wensu of the School of Life Sciences of Tianjin University proposed a simple strategy to make the silk strength 70% higher than that of natural spider si

Silk is a protein fiber coagulated by the silk liquid secreted by mature silkworms when they form cocoons, also known as natural silk. Silk is one of the products of civilization in ancient China. For thousands of years, it has been used as a source of material for luxury clothing supplies for royal and nobles. Today, in addition to being used as textile fabrics, silk has been widely used in the field of biomedical because of its characteristics such as biocompatibility and biodegradation, such as as a material for surgical sutures and patches. In addition, it is used in tissue regeneration experiments. However, due to the softness of the silk, the tensile strength is lacking. Therefore, the biggest advantage has also become its biggest disadvantage.

In recent years, researchers have found through comparison that the strength of silk is significantly lower than that of all kinds of spider silk , but due to the spider's too aggressive habit, it is impossible to raise artificially. Scientists then thought of a second-hand approach: implant the spider's DNA into the body of silkworm , but this is an expensive and difficult process to scale.

On October 7, Beijing time, in a latest study published on Matter , a research team led by Professor Lin Zhi and Professor Yuan Wensu of Tianjin University proposed a simple strategy to make the strength of silk 70% higher than that of natural spider silk. This approach reverses the previous view that silk is not comparable to spider silk in mechanical properties and opens a door to mass production of high-performance and cost-effective silk-based materials.

Silk fibroprotein (RSF) is a natural polymer fibrin extracted from silk, and the content accounts for about 70%-80% of silk. When the silkworm transforms into a moth form, it uses soft silk rich in silk fibroin to build cotton ball-shaped cocoons.

In this new study, the team was inspired by artificial spinning of the structure of spider silk egg bag silk and developed a simple strategy to spin super-strong silk fibers in a metal ion solidification bath using regenerated silk fibroin.

Natural silk fiber consists of a fiber core wrapped in silk glue , but silk glue usually interferes with the spinning of commercial fibers. To solve this problem, first, the researchers regenerate silk fibroin through degumming and dissolving processes. Previous studies have shown that the degumming process can easily lead to breaking of disulfide bonds in the peptide and molecules, resulting in more chain ends in the fiber. Therefore, the artificial fiber spun from degraded silk fibroin cannot have a high tensile strength. To this end, the researchers achieved the optimal degumming ratio with minimal degradation by appropriately controlling the degumming temperature and time using the specific chemical reagent or proteolytic enzyme .

Then, to enhance the silk quality used for spinning, the researchers spun super-strong silk fibers using regenerated silk fibers in a metal ion solidification bath. The test results show that the tensile strength of rayon , , reaches about 2.0 GPa, which is more than 70% higher than the average toughness of spider silk. It also exhibits an average Young's modulus (physical amount of solid materials' ability to resist deformation) , which is significantly higher than all known natural spider silk.

was observed under a microscope and the researchers described it as a "smooth and strong" material, indicating that this rayon can withstand external forces.

structural analysis showed that the extraordinary strength of rayon may be attributed to the high crystallinity and small nanocrystals formed in artificial fibers. During spinning and after spinning, Zn2+ ions are incorporated into the fibers, which may also contribute to their excellent mechanical properties.

In summary, the team reported a simple strategy to spin super-strength rayon using low-cost undegraded silk fibroin and metal ion solidification baths. The tensile strength of this rayon can significantly exceed the strongest known spider silk. Therefore, this new approach opens a promising door to mass production of cost-effective high-performance wire-based materials.

paper link:

https://doi.org/10.1016/j.matt.2022.08.028