To date, a myriad of possible uses for spider silk have been proposed — including medical applications, cosmetics, composite materials for aircraft, protective body armor and incorporation into textiles.
If you scour the maker space, you can easily identify up to 10 companies already using spider silk for these various applications. These companies have developed industrial-scale processes to ferment synthetic spider silk in bacteria. The result is a growing industry of sustainably sourced and environmentally friendly material that can supplant other raw materials limited by finite availability. The other aspect of spider silk is that it holds the promise of delivering impressive new functionalities and features for different types of applications.
With these existing capabilities, why invest further in spider silk research? Most companies to date are only now getting a grasp of how to reliably make spider silk through batch fermentation without any enhanced features or functionality. An individual spider can make up to eight different silks that all have distinct uses, many of which scientists are still seeking to characterize. To successfully implement silk into any system, researchers need an in-detail quantitative, correlative, and causal understanding of the interplay of the different sequence motives and scales, which govern the tuning of the tensile properties. So far, only limited information on selected silks from a small number of spider species is available.
Spiders have evolved silks, such as their dragline silk, that uniquely combine tensile strength and extensibility, placing them among the toughest natural fiber materials on earth. They even surpass most fabricated materials, like Kevlar, while being sustainable and thus of significance for materials researchers in this age of global environmental concern. The challenge has been to translate that potential into reality: While Spider-Man’s web-shooting silks may appear to stop an out-of-control car on the spot on the big screen, in reality the spider silk would stop the car successfully several hundred feet following the point of impact. While many companies are producing simple spider silks, a lot more work needs to be done to reach functionalities that could contend with Spider-Man’s versatile silk.
The Office of Naval Research (ONR) Global, in partnership with the Air Force Office of Scientific Research (AFOSR), is sponsoring the revolutionary work of Dr. Thomas Scheibel, professor for biomaterials and head of the Biomaterials Department at the University of Bayreuth, Germany. This project aims to further understand the spider dragline silks’ structure-function relationship by investigating its different hierarchical levels comprehensively and in depth, using both a correlative as well as a design approach.
Dragline silk, also called major ampullate silk, of eight to 10 closely related spider species will be selected for the investigation of their primary, secondary and quaternary structure, using a wide array of techniques: RNA sequencing, synchrotron-based X-ray scattering, nuclear magnetic resonance (NMR), thermal analysis, electron and force microscopy, and static and dynamic tensile testing. The influence of the investigated structures and their interdependence on silk tensile properties will be analyzed with a regression model. This project will be the first to obtain data of sufficient resolution to develop a predictive model, which can estimate the impact of changes in elementary building blocks on the molecular level on tensile properties at the macroscopic scale.
In parallel, a husbandry regime of select spider species will facilitate the manipulation of specific silk and silk-related sequences to deduce their role in silk functionality. Predictions based on regression analysis will be used to test the limits of silk tuning, and novel functionalities can be produced by inserting non-native sequence elements. This newly created model spider system is not limited to fundamental silk research — it will find wide applicability in the study of spider biology.
Scheibel stated, “If we are successful, we can create a model system in which frame-shift mutations, point mutations, in-frame deletions and insertions can be produced in silk and silk related genes to facilitate the investigation of the spider silk´s structure function relationship.”
So what does all of this investment promise to deliver? The tools of synthetic biology have shown great potential in allowing us to apply engineering concepts to biological processes. The result is scientists are able to produce biological material by design with enhanced functionalities. Spider silk is one such example, where novel materials can be sustainably sourced for applications in the automotive, air and space, textile industries, plastics and other areas.
This ONR Global/AFOSR-funded project will provide critical knowledge on the structure-function relationship of silk to accelerate the development of silk-based materials far beyond what is currently possible. The key of Scheibel’s work will be to describe how spider silks’ elementary building blocks can be implemented intelligently and efficiently into established platform-technology of recombinant silk protein production, to generate materials with fine-tunable properties at large scale.
Spun into fibers or printed as gels, they can be used to improve existing and develop new applications that could prove invaluable equally to the civilian population as well as for military applications. Examples include applications in medicine, such as scaffolds for bone regeneration; in optics and electronics, as biomimetic muscles for robotics; and as high-tech threads and textiles, as are needed for parachutes, bulletproof vests or mobile shelters.
Dr. Patrick Rose is science director for synthetic biology at ONR Global. ONR Global sponsors scientific efforts outside of the U.S., working with scientists and partners worldwide to discover and advance naval capabilities.
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