Engineered Spider Silk—Inspired by Nature and Made in the Lab

According to “Fragments of Spider Lore,” an article in Natural History Magazine, “…in the sacred writings of ancient India…a large spider was the [creator] of the universe. From her glands she wove the web of which we inhabit a part, and even now she sits in its center directing its motion.” Throughout cultural and literary history, the fine, silky, strong fibers spun by spiders have formed the basis for creation stories, promoted healing in the wounded, protected the pursued from the pursuer during conflict—and inspired scientists to analyze and try to reproduce their work in the lab. A polymer protein fiber, spider silk’s elasticity and tensile strength are derived from its chemical composition, chiefly alanine (C₃H₇NO₂) and glycine (C₂H₅NO₂), amino acids that, along with the fiber’s high molecular weight and repetitive protein sequences (spidroins), contribute to its coveted mechanical features. Mass harvesting and spider farming, or the economically unfeasible and laborious gathering of silk from cannibalistic, living arachnids for commercial purposes, remains a matter of science fiction. In Back to Nature: Textile Fibers Come Full Circle, an article authored by Maria Thiry for the AATCC Review and published in January 2004, fiber experts and scientists discussed how engineered spider silk could be created in the lab and its potential end uses. In this update, we’ll talk about the 20-year effort to make engineered spider silk at an industrial scale a reality.   Image 1: Structure of Spider Silk A strand of natural spider silk, for example, dragline silk, is approximately 3-3-5 micrometers in diameter and composed of a hydrophobic lipid coat, glycoproteins, and the “skin,” which functions as a biological barrier, protecting the main proteins or spidroins. Image is in the public domain.    

Born to Spin

Arachnids produce spidroins by way of the internal glands located in their abdomens, where they store their liquid silk proteins (spin dope). They extrude the stored proteins through spinnerets, or silk-producing organs, located at the back of their abdominal undersides, using their legs and weight-bearing abilities to affect a push-pull motion. As the extruded liquid silk exits the spinnerets, spiders experience changes in their internal abdominal pressure and shear stress, and the liquid silk gets a decrease in pH, thereby transforming the latter into a fiber.     Image 2: Main Organs of a Spider The main organs of a spider include the spinneret (12) and the silk gland (13) Image is in the public domain.       By comparison, a genetically engineered recombinant spider silk protein (rSSP) is based on a donor-recipient relationship requiring feedstock and a host. In a heterologous expression system used to create spider silk, a deoxyribonucleic acid (DNA) sequence or genetic material imported from an orb-weaving spider is inserted into a host cell or species, for example:

• Bacteria like Escherichia coli(E.coli)
• Cell lines, such as the Bombyx mori (BmN) found in a silkworm’s ovarian tissue
• Transgenic animals (goats, mice, sheep, and silkworms) and plants (tobacco)
• Yeasts

The result is a transgenic organism with a new skill set ready for fermentation in a bioreactor. The rSSP produced is in the form of a powder, which is then combined with a solvent and extruded, or wet spun, through a die or needle to create a fiber. In November 2025,  Todd Blackledge,  Integrated Bioscience Director in the Department of Biology at The University of Akron, was asked about how our understanding of how the DNA sequences in spider silk have evolved. According to Blackledge, “The tools available to biologists to work with genomes and to understand gene expression are exponentially more advanced than 20 years ago. Back then, scientists worked really hard to sequence [a mere portion] of a silk gene (which are very big genes) from a large amount of silk gland tissue. This gave [them] a good picture of the structure of the central portions of silk genes, which led to foundational hypotheses about how amino acid sequences of silk proteins related to different material properties. “Now it’s possible to sequence entire silk genes from the beginning to the end, including parts of genes that are not translated into proteins but are essential for controlling that process. This [is significant] because we now understand much more about how the N and C terminal regions of silk proteins (think of them as the endcaps of the proteins) play essential roles in the spinning of silk fibers from the liquid dope. The level of resolution is also much greater, to the point that it’s possible to explore differences in silk gene expression among the regions of a silk gland. As the diversity of known spider silk genes has exploded over the last few years, understanding where and when different versions of similar-looking silk genes are expressed in silk glands is important.”     Image 3: Spinning Mechanism in a Spider The C and N terminuses in the silk proteins found in a spider’s spinning mechanism play key roles when transforming liquid dope into a fiber. Image is in the public domain.       When asked if there were any heterologous expression systems or hosts that no longer had potential, Blackledge said, “The tools for this research are vastly improved. The field has shifted away from the mammal models to focus on systems that are easier to work with in terms of potentially scaling up production and harvesting silk. Most of the current work that I see focuses on bacteria, yeast, and silkworms.”   

“Aha” Moments: Discoveries and Pioneers

In 2007, while a professor at the Technical University at Munich (TUM) in Germany, Thomas Scheibel and his co-inventors filed a patent for a pioneering biotechnical production process. Here, genetically engineered E.coli bacterial hosts were used to create silk proteins that, following fermenting and spinning, yielded fibers similar to their natural counterparts. The following year, Scheibel co-founded AMSilk GmbH, which currently offers two biodegradable, biopolymer vegan yarns: Biosteel and Ultrafine. Commercial collaborations include those with Adidas, Omega, and Mercedes Benz to create concept performance shoes (2016), limited-edition watchbands (2019), and door pulls (2022), respectively. At Bolt Threads (est. 2009) in Berkeley, CA, USA, creators of Microsilk, bioengineered genes, replicas of the proteins found in spider silk, are inserted into yeast, after which, the host is combined with corn-based sugar and water, and the protein is fermented in large quantities. The isolated and purified silk proteins are then spun into fibers. In 2017, Bolt Thread’s knitted, limited-edition neckties were “the very first commercially available product made of [bioengineered] spider silk,” as stated on its website. Instead of bacteria or yeast, at Kraig Biocraft Labs (est. 2006) in Ann Arbor, MI, USA, domesticated, transgenic silkworms function as the hosts, generating fibroin, an insoluble protein, also in mass quantities. The end products, including Dragon Silk and Monster Silk_, are composite fibers made from silkworm and spider silk proteins. As reported on the company’s website, in its first commercial endeavor, Kraig Biocraft Labs is poised to fulfill an order for an athletic apparel company, the details of which remain confidential.     Image: 4 Transgenic Silkworms At Kraig Biocraft Labs, transgenic silkworms are used to make Monster Silk. Here, they’re shown transitioning into moths. Image is in the public domain.    

Spiber: One Company’s Spider Silk and Protein Journey

Although Spiber (est. 2007) in Tsuruoka, Yamagata, Japan, began as a student project at Keio University in 2004 with the goal of replicating spider silk in the lab, Kenji Higashi, Representative of Spiber Europe, explained that, “We don’t think of ourselves as a ‘spider silk company’ anymore. We see ourselves as building a broader platform for designed protein materials. Originally, as spider silks are famous for their toughness, [our goal] was to make a super-tough fiber for industrial applications. “After years of work, we managed to produce small amounts of recombinant spider silk proteins for prototype fibers and fabrics. [While beautiful and fine, they were] nowhere near as tough as the best natural silks.” After studying spider biology in depth and trying to mimic how spiders spin their fibers, the Spiber team eventually realized that even a lab-developed protein that perfectly replicates the amino-acid sequence of natural spider silk, without the equivalent of a spider’s spinning apparatus, reproducing the fiber’s properties remained beyond reach. As the company continued to explore potential applications for their technology, they came to the conclusion that many products, like apparel textiles, don’t necessarily require the use of super-tough fibers— “as long as they have the right properties and are strong enough to process into garments.” So, instead of attempting to copy a spider’s work in the lab, Spiber began designing their own proteins that “went beyond what exists in nature [and] made major changes to their amino acid designs. The Brewed Protein fiber we produce today,” Higashi states, “draws inspiration from spiders, silkworms, and other organisms, but the sequences are engineered to meet [specific end uses and goals], such as performance/comfort in textile products and production efficiency. On the technical side,” he added, “Spiber has already demonstrated that it’s possible to produce protein fibers to make practical garments at commercial scale.” Noteworthy collaborations have included those with companies like Burberry, Goldwin, and The North Face, and fashion designers such as Yohji Yamamoto and Iris van Herpen, whose couture wedding dress featured in her Autumn/Winter 2025 show, was made using Spiber’s protein fibers.  Images 5a and 5b: Brewed Protein Staple Fiber (left) and Moon Parka (right) Left: Brewed Protein is made from plant-based materials (sugars) and processed by means of precision fermentation. It can be used as a coating, fiber, or membrane. Right: The limited edition Moon Parka (50 items), released in Dec. 2019, was manufactured using Brewed Protein. Moon Parka is a trademark of Spiber Inc. and Goldwin Inc. Images courtesy of Kenji Higashi, Representative of Spiber Europe.   And while Spiber’s protein-producing process “still needs some input sugars as nutrients for our microbes,” Higashi notes that, “our life-cycle assessment (LCA) work shows that equivalent amounts of protein fibers can be delivered with a smaller environmental footprint compared to animal-based systems… and precision fermentation a far more efficient use of land and resources. The challenge now,” he emphasized, “is less ‘can we make the material’ and more ‘how quickly can we make it mainstream.’”  

Web Tests and Threats

According to Katrina Penegar, Testing Lab Manager at the Textile Technology Center at Gaston College (Kimbrell Campus) in Dallas, NC, USA, “ASTM D2256 (Standard Test Method for Tensile Properties of Yarns by the Single-Strand Method) should be able to assess the tensile strength of genetically engineered or synthetic spider silk” destined for commercial applications. As described by Penegar, “The single-strand method involves mounting an individual yarn in a tensile tester, applying a controlled rate of extension until break, and recording force and elongation. This helps determine properties such as tenacity, elongation, and modulus.” However, Penegar noted, “ASTM D3822 (Tensile Properties of Single Textile Fibers) may be a slightly better option. This would depend on the sample type, for instance, if you have an actual yarn or single fibers. This method would also be dependent on the strength, length, and size of the sample…parameters [that] could limit which equipment is viable to get the results needed.” And while Penegar’s lab has yet to test any spider silk samples in-house, “based on high-performance fibers, challenges often include securing delicate filaments without inducing stress or slippage. [Additionally], specialized grips and careful alignment are critical to avoid premature breakage.” In the natural world, dew and rain can break or destroy a spider’s web, no matter its tensile strength. As Higashi at Spiber affirmed, “When we first started developing textiles for apparel applications using our early spider‑silk‑inspired protein polymers, we were able to make beautiful fabrics, but when wet, they shrank—a lot. Natural spider silks have a built-in function [that] automatically adjusts their tension when they [come] in contact with water or when [exposed to changes in humidity]. This phenomenon is known as supercontraction, which most likely evolved as a way for spiders to keep their webs working with [minimal] maintenance. [While] useful for a spider in the wild, it’s not ideal for a sweater that has to survive home laundering.” While conventional fibers and fabrics subjected to dyeing may undergo test methods like TM061 Test Method for Colorfastness to Laundering: Accelerated or TM107 Test Method for Colorfastness to Water, as far as Matthew Marshall, Chair of RA23 Colorfastness to Water Test Methods Committee and Technical Manager—Softlines at UL Solutions in Wilmington, DE, USA, knows, committee members have not conducted any research that involved colorfastness and engineered spider silk, specifically for TM107. So, as of this writing, we don’t know if the aforementioned hypothetical sweater would survive the rigors of hand or machine washing.  

Engineered Spider Silk: Rethinking the Possibilities…

“Spiders,” Kenji Higashi reminds us, “have spent hundreds of millions of years of evolution refining their spinning process. The way that polymers align and crystallize as spiders pull out their silks is extremely intricate, and we don’t yet know how to replicate that process in an industrial spinning environment.” Relatively recent, small-scale projects have included a microfluidic artificial silk gland, a collaborative effort between the Center for Sustainable Resource Science and Pioneering Research Cluster at RIKEN, a National Research and Development Agency in Japan. In a Jan. 25, 2024, press release, the agency stated that the goal of the device was to recreate “the complex molecular structure of silk by mimicking the…chemical and physical changes that naturally occur in a spider’s silk gland.” In order for this device to have the “real-world impact” research leader Keiji Numata referred to in the press release, the team will have to “scale-up [its] fiber-production methodology and make it a continuous process…and evaluate the quality of [their] artificial spider silk.” In Back to Nature: Textile Fibers Come Full Circle, Todd Blackledge mentioned some potential end-uses for engineered or synthetic spider silk in the real world, including bullet-resistant armor, high-performance cables and ropes, emergency bandages, and performance wear. In 2025, are those commercial applications still viable? “I think the field has moved away from a ‘what can we do with the super properties of spider silk’ approach to ‘what is economically viable in current market conditions,’” Blackledge said. “Industry already has a [lot] of easily manufactured petroleum-based synthetic fibers, and medicine has many different suture and bandage materials on the market. So, the real question is, where can synthetic spider silk provide enough added value that it’s worthwhile for industry to pay the cost to transition from existing supply chains?” As such, “current efforts to market spider silk products focus more on additives in cosmetic products, luxury applications, and vegan alternatives to silkworm products.”  

…And Continuing to Find Inspiration in Nature

That said, Kenji Higashi of Spiber believes “that the development of engineered/synthetic protein fibers is definitely worth pursuing. One of the key lessons from our two decades of work has been that trying to copy the exact way that nature does things can be less important than learning from nature’s designs.”        

Image: Golden Orb Weaver

Golden orb spider at work (Nephila Clavata)

           

About the Author

Juliana Barnes, a freelance writer and graduate of the Fashion Institute of Technology’s textile design program (concentration in woven design), has more than 12 years of experience in e-learning and information services.