Engineers from Washington University in St. Louis just made a new fiber that is tougher and stronger than natural spider silks, dubbed as the toughest and strongest materials on Earth.

This new fiber is made from genetically engineered bacteria that are stronger than steel and tougher than Kevlar. The team published their study, "Microbially Synthesized Polymeric Amyloid Fiber Promotes β-Nanocrystal Formation and Displays Gigapascal Tensile Strength," in ACS Nano.

Polymeric Amyloid Fiber

The yielded fiber or artificial silk is known as "polymeric amyloid" fiber. It was not technically produced by the engineers but by the engineered bacteria from the laboratory of Professor Fuzhong Zhang from the Department of Energy, Environmental &Chemical Engineering, McKelvey School of Engineering, Washington University in St. Louis.

According to Science Daily, Zhang has worked with spider silk before; an example is the recombinant spider silk he created using the lab-engineered bacteria in 2018. It is said that the bacteria-based fiber has strength that is at par with its natural counterparts in all of the critical mechanical properties.

"After our previous work, I wondered if we could create something better than spider silk using our synthetic biology platform," Zhang said as quoted by the science website.

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Making A Stronger Fiber

Zhang's team, including Ph.D. student and first author of the study Jingyao Li, altered the amino acid sequence of spider silk proteins to develop new properties and make sure that the attractive features of spider silk will still be there.

 The team wanted to resolve the demand for producing the main component of natural spider silk that provides its strength, the β-nanocrystals. They redesigned the silk sequence by incorporating an amyloid sequence with a high tendency to develop β-nanocrystals, according to AZN Nano.

It produced various polymeric amyloid proteins with a low repetitive amino acid sequence compared to the spider silk that enables easier production using engineered bacteria. These bacteria generated hybrid polymeric amyloid proteins with 128 repeating units that yielded a fiber with a gigapascal strength. That means it is stronger than common steel and that of the natural spider silk fibers.

Other researchers that are part of the study were professor Young-Shin Jun and her Ph.D. student Yaguang Zhu who, together with Zhang and Li, ascertained that the high mechanical properties of the polymeric amyloid fibers are made from the improved quantity of β-nanocrystals.

But like many things, Zhang's high-performance synthetic fibers still have the potential to be improved. Zhang said that this only demonstrates that biology can be engineered to develop better materials than the best material found in nature.

They just found three out of thousands of amyloid sequences that can improve the features of the natural spider silk.

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