Scientists are closer to unlocking the secrets of the strongest spider silk in the world

In the world of materials science, spider silk is fascinating. It’s a material that’s super strong, incredibly light, and remarkably flexible. Yet, despite the tireless efforts of many researchers, the complex process spiders use to create this extraordinary substance remains a mystery. 

If scientists can crack the code, synthetic spider silk would revolutionize industries, displacing Kevlar, polyester, and carbon fiber. This material could transform everything from the production of bulletproof vests to construction materials.

Biophysicist Irina Iachina has been studying spider silk since her master’s degree at the University of Southern Denmark (SDU). She now carries out her research at the Massachusetts Institute of Technology, with financial backing from the Villum Foundation.

In collaboration with fellow SDU biophysicist Jonathan Brewer, Iachina has recently made an unprecedented breakthrough in her spider silk investigation. 

For the first time, the pair has managed to delve into the interior structure of spider silk without having to cut or damage the fiber in any way. The groundbreaking research is published in the journal Scientific Reports.

How the study was conducted

“We have utilized multiple advanced microscopy techniques, and we have also created a novel type of optical microscope that allows us to peer deep within a fiber and visualize its internal structure,” explained Brewer.

Earlier attempts at analyzing spider silk utilized methods that required slicing open the fiber to capture a cross-section, or even freezing the samples. While these methods provided novel insights, Brewer points out the obvious drawbacks. 

The processes invariably altered the natural structure of the silk, potentially skewing the findings. “We aspired to examine pure, unadulterated fibers that haven’t been cut, frozen, or manipulated in any manner,” said Iachina.

To avoid the need for invasive procedures, the team employed techniques such as Coherent Anti-Stokes Raman Scattering, Confocal Microscopy, Ultra-resolution Confocal Reflection Fluorescence Depletion Microscopy, Scanning Helium Ion Microscopy, and Helium Ion Sputtering.

What the researchers discovered 

The investigations led to the discovery that spider silk fibers consist of at least two outer lipid (fat) layers. Beyond these layers, within the fiber, there are multitudinous tightly packed fibrils in a linear arrangement. 

These fibrils, with diameters between 100 and 150 nanometers, are beyond the measurement capabilities of conventional light microscopes. “They aren’t twisted as we might have imagined, which informs us that there’s no necessity to twist them while creating synthetic spider silk,” said Iachina.

The research was specifically focused on the silk from the golden orb-web spider, Nephila Madagascariensis, which produces two distinct silk types.

Major Ampullate Silk fibers (MAS) is used to build the spider’s web and serve as a lifeline. It is robust with a diameter of around 10 micrometers. Minor Ampullate Silk fibers (MiS) is used for auxiliary construction. It is more elastic with a typical diameter of five micrometers.

The analysis has revealed that the MAS silk contains fibrils with a diameter of approximately 145 nanometers, while for MiS, it’s around 116 nanometers. These fibrils are comprised of multiple proteins, generated by the spider during silk production.

New insights

Gaining an understanding of how these strong fibers are created is crucial, yet the manufacture of these fibers also poses a significant challenge. Given these difficulties, many researchers depend on the spiders themselves to yield the silk required for study.

However, as technology evolves, there’s a promising alternative. Many researchers are now turning to the realm of computational science, and Iachina is at the forefront of this transition at MIT.

She is conducting computer simulations to understand the transformation of proteins into silk, a project that promises to unlock new insights into this enigmatic material.

“Currently, I’m engrossed in computer simulations of protein-to-silk transformation. The overarching objective, naturally, is to ascertain how to synthesize artificial spider silk. But beyond this, I’m profoundly committed to fostering a broader understanding of the world we inhabit,” said Iachina.

More about spider silk

Spider silk is a protein fiber spun by spiders. Spiders use their silk to make webs or other structures, which serve as both a home and an effective trap for catching their prey. There are around 35,000 species of spiders, each spinning its own unique type of silk.

Spider silk is noteworthy for its remarkable characteristics. It’s renowned for its strength and resilience. On a weight-to-weight basis, it is stronger than steel and tougher than Kevlar. The exact properties can vary, but all spider silks have some degree of strength, flexibility, and elasticity. 

The silk also has a very high tensile strength, meaning it can be stretched a long way before it breaks. These traits vary depending on the type of silk a spider produces, with some silks being stronger or more elastic than others.

The silk’s strength comes from the highly organized arrangement of proteins within the silk fibers. These proteins form complex structures that lend the silk its incredible durability and elasticity.

In the SDU study, the scientists discovered that spider silk is composed of at least two outer layers of lipids (fats) and numerous tightly packed fibrils inside.

In addition to its mechanical properties, spider silk has a number of other interesting features. It’s incredibly lightweight; a strand long enough to circle the Earth would weigh less than 500 grams.

Spider silk is also biodegradable and biocompatible, which opens the possibility for various medical applications such as sutures, artificial ligaments, or tissue scaffolds.

Despite the significant scientific and industrial interest, producing spider silk on a large scale is challenging. Unlike silkworms, spiders can’t be farmed for their silk as they tend to be territorial and cannibalistic. 

Synthetic production also poses its own set of challenges due to the complex protein structure of the silk. However, ongoing research continues to bring us closer to understanding the secrets of spider silk and how to produce it artificially. If successful, this could lead to a new generation of materials with extraordinary properties.

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