Scientists Are One Step Closer To Replicating Spider Silk

For the first time, researchers have been able to study the internal workings of unprocessed spider silk. While previous work has examined frozen cross-sections of spider silk samples, researchers from the University of Southern Denmark say that their new studies – published in the journals Scientific Reports and Scanning – provide additional data that could help with the production of synthetic spider silks strong enough to replace materials like Kevlar, polyester and carbon fiber. 

Silk that is stronger than steel

Spider silk has a complex combination of properties that have fascinated scientists for decades. High in strength, lightweight and super flexible, this natural fiber is remarkably difficult to replicate synthetically.

This is an issue because, unlike silkworms, spiders sometimes exhibit cannibalistic behavior and so cannot be easily farmed. To satisfy the demand in areas where such a fiber would be useful, a suitable synthetic substitute is critical. But current efforts to produce such a synthetic alternative have not achieved any amount of widespread success.

With these efforts, scientists began to take a closer look at the strongest silks being produced naturally by different spider species. Such studies have generated a lot of new insights. However, the techniques used for these studies tended to require that silk samples be cut open to achieve a good cross-section, or that they be frozen. Both of these approaches risk altering the structure of the silk fiber before it can be properly analyzed.

Now, researchers from the University of Southern Denmark (SDU) have demonstrated that it is possible to examine the internal structures of spider silk using minimally invasive, or non-invasive, analytical techniques.

“We wanted to study pure and unmanipulated fibers that have not been cut, frozen or manipulated in any way,” said study author Irina Iachina, a postdoc and biophysicist in the SDU Department of Biochemistry and Molecular Biology.

Spider silk consists of a double outer layer and tightly packed fibrils

In these new studies, the researchers examined the silk produced by the golden orb-web spider, Nephila madagascariensis.

This species produces two types of silk. Its Major Ampullate Silk (MAS) fibers are very strong and form the basis of the spider’s web. The rest of the web is constructed using Minor Ampullate Silk (MiS), which is thinner and less strong, but has a higher elasticity that is useful for the web’s construction and function.

To study these two silk types, the researchers used coherent anti-stokes raman scattering, confocal microscopy, ultra-resolution confocal reflection fluorescence depletion microscopy, scanning helium ion microscopy and helium ion sputtering techniques.

“We have used several advanced microscopy techniques, and we have also developed a new kind of optical microscope that allows us to look all the way into a piece of fiber and see what's inside,” said senior author Jonathan Brewer, an associate professor and research leader at the SDU Department of Biochemistry and Molecular Biology. Brewer is also the director of the Danish Molecular Biomedical Imaging Center.

The SDU researchers found that the spider’s silk is made up of two distinct outer layers of lipids, i.e. fats. The inner core of the silk fiber consists of numerous “crystalline fibrils”, which are tightly packed together and surrounded by amorphous protein regions. Importantly, these fibrils run parallel to each other along the long axis of the silk fiber, with no twisting or other unique conformation that could be contributing to the silk’s unique properties. 

“They are not twisted, which one might have imagined, so now we know that there is no need to twist them when attempting to create synthetic spider silk,” Iachina said.

According to the researchers’ analysis, the fibrils in the MAS silk fiber have a diameter of approximately 145 nanometers. By comparison, the fibrils in the MiS fiber are thinner, at around 116 nanometers in diameter. 

Producing new synthetic silks

The fibrils contained in these silk fibers are made up of several different proteins, all produced by the spider as it spins its web. While improving scientists’ understanding of silk structure can be one way to further the current generation of synthetic fabrics, researchers are also hoping to unravel the processes governing how spiders create their silk in the first place. 

“Right now, I am doing computer simulations of how proteins transform into silk,” Iachina said. “The goal is, of course, to learn how to produce artificial spider silk, but I am also interested in contributing to a greater understanding of the world around us.”

References: Iachina I, Fiutowski J, Rubahn HG, Vollrath F, Brewer JR. Nanoscale imaging of major and minor ampullate silk from the orb-web spider Nephila madagascariensis. Sci Rep. 2023;13(1):6695. doi: 10.1038/s41598-023-33839-z

Iachina I, Brewer JR, Rubahn HG, Fiutowski J. Helium ion microscopy and sectioning of spider silk. Scanning. 2023;2023:e2936788. doi: 10.1155/2023/2936788

This article is a rework of a press release issued by the University of Southern Denmark. Material has been edited for length and content.