Invulnerable? Modifying microorganisms to produce artificial muscle fibers, which are tougher than Kevlar, the “Armored Guardian”

  Recently, Chinese professor Fuzhong Zhang, as the corresponding author, published a paper on Nature Communications titled “Microbial production of fibronectin fiber has superior mechanical properties”. The paper describes the team’s use of synthetic biology methods to polymerize proteins. Inside the engineered microorganism. Using this technology, the research team designed the microbial production of high-molecular-weight titin, which was then spun into fibers.
  Tests have shown that these fibers are superior to many synthetic and natural polymers.
  Fuzhong Zhang became an assistant professor in the Department of Energy, Environment and Chemical Engineering at Washington University in St. Louis in 2012, focusing on research in the field of synthetic biology. Previously, he used microbial methods to produce artificial spider silk that was tougher than spider silk.

Fuzhong Zhang
1 stronger than Kevlar

  Artificial muscle fibers have always been a topic of interest to people. Researchers try to design materials with similar characteristics to muscles to meet various application scenarios, such as soft robots. Previously, MIT researchers used ordinary nylon fibers to make artificial muscle fibers, which can simulate the skills of natural muscle tissue bending motion characteristics.
  The artificial muscle fibers produced by the Fuzhong Zhang team using microorganisms are stronger than cotton, silk, nylon, and even Kevlar.
  Kevlar is a new type of aramid fiber composite material developed by DuPont in the 1960s. This new type of material has low density, high strength, good toughness, high temperature resistance, easy processing and molding, and its strength is of the same quality. Five times that of steel, but the density is only 1/5 of that of steel. Because the materials of Kevlar brand products are tough, wear-resistant, rigid and flexible, they have the special ability of invulnerability. In the military, it is called an “armor guard” and is often compared with carbon fiber.


Schematic diagram of the multi-scale structure of muscle and the silicon-based polymerization of muscle protein in E. coli

  The paper stated that although engineered microorganisms have now been used to reproducibly produce many small molecules, the direct microbial synthesis of high-performance polymer materials is still a challenge.
  Researchers have designed the muscle protein polymer produced by microorganisms to produce high-performance fibers. It not only has the highly desirable properties of natural muscle protein (that is, high damping capacity and mechanical recovery), but also has high strength, toughness and damping energy. It is used in many synthetic and natural polymers.
  The key to creating this material is the production of Titin, which is the largest protein known.
  Engineered microorganisms can be used for the large-scale production of some small molecule compounds, and the production of huge proteins still faces many challenges.
  The researchers pointed out that “due to genetic instability, low translation efficiency, and metabolic burden, these ultra-high molecular weight repetitive proteins are extremely difficult to produce in microorganisms.”
  In order to avoid some of the problems that usually hinder the production of large proteins by bacteria, the research team designed a Bacteria splice small fragments of titin to form an ultra-high molecular weight polymer about 2 megadaltons, which is about 50 times the size of a typical bacterial protein. Then, they used a wet spinning process to convert the protein into fibers about 10 microns in diameter, equivalent to one-tenth the thickness of a human hair.
2 The first to produce engineered macroscopic materials from Titin

  Researchers analyzed the structure of these fibers and determined the molecular mechanism of their unique toughness, strength, and damping ability.
  Structural analysis revealed that these fibronectin fibers contain axially aligned, side-by-side pairs of Ig-like domains.
  The researchers wrote: “Structural analysis and molecular modeling show that these properties are derived from the unique interchain crystallization of folded immunoglobulin-like domains, which can resist interchain slippage while allowing intrachain unfolding.” The
  researchers said, This achievement represents the first example of engineered macromaterials produced from tyin.

  The mechanical test of ultra-high molecular weight muscle protein fibers produced by microorganisms shows that the fibers have high toughness, damping ability and mechanical recovery, which can be compared with natural muscle fibers.
  ”By using the biosynthetic ability of microorganisms, this work has produced a new type of High-performance material, this material not only has the most ideal mechanical properties of natural muscle fibers (that is, high damping capacity and rapid mechanical recovery), but also has high strength and toughness, even higher than many man-made and natural high-performance fibers.” They wrote.
3 Wide range of applications

  The author points out that biology has always been the source of inspiration for material design. In nature, there are many examples of producing biodegradable materials from renewable raw materials through low-consumption, high-performance, and biodegradable processes, such as extremely tough insect silk, underwater adhered mussels, and compression-resistant pearl abalone. , Insect arthropod elastin.
  ”In many cases, the performance of these natural materials is better than the best existing petroleum-based products. However, many high-performance natural materials cannot be obtained directly from primary sources. Therefore, the use of microbial production can promote these high-performance renewable materials. Development.” The researcher added.
  As for the application field of the fiber, the researchers said that this material can be used in the biomedical field in addition to the possibility of making clothes or protective armor.
  Since it is almost the same as the protein in muscle tissue, this synthetic material may be biocompatible, so it may be a material for sutures, tissue engineering, and so on. “The perfect combination of mechanical properties, sustainable production processes, and biodegradability of this fiber enables applications ranging from biomedicine to commercial textiles (such as anti-ballistic materials, meshes, sutures, and tissue engineering),” the team further Said.
  ”It can achieve low-cost, large-scale production,” Fuzhong Zhang said, “This may realize many of the applications that people have thought of using natural muscle fibers.”
  Fuzhong Zhang’s research team does not intend to stop at artificial muscle fibers. It may be possible in the future There will be more unique materials. Several researchers have applied for patents based on this research.

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