Engineers at Washington University in St. Louis have developed a new amyloid-silk hybrid protein and manufactured the protein in artificial bacteria. The fibers resulting from the material are stronger and more resistant than natural spider silks. Spider silk is considered to be one of the strongest and most resilient materials in the world. The rayon is known as « polymetric amyloid » fiber.
The fibers are made by bacteria that have been genetically engineered in Professor Fuzhong Zhang’s laboratory. Zhang has worked with spider silk in the past and in 2018 developed bacteria in his laboratory that produced a recombinant spider silk with a performance similar to that of natural counterparts in all important mechanical properties. Zhang said he wondered if the team could use the synthetic technology platform they developed to create something better than spider silk.
The team had to overcome a significant recombinant spider silk fiber challenge without making significant modifications to create the beta nanocrystals that are the main constituent of natural spider silk and that give the material its strength. To overcome this challenge, the team created various polymetric amyloid proteins using three well-studied amyloid sequences.
Proteins that result from the process have less repetitive amino acid sequences than spider silk, making them easier for bacteria to produce. Ultimately, the process produced a hybrid polymer amyloid protein with 128 repeating units. The longer the protein, the stronger and tougher the resulting fiber.
The researchers find that the 128 repeated proteins resulted in a fiber with a gigapascal strength that is higher than that of ordinary steel. It also had higher toughness than Kevlar and all previous recombinant silk fibers. The team says they are just beginning their research, and their discovery shows that they can evolve biology to produce materials that outperform the best materials available in nature.
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