Researchers from the Washington University in St. Louis have successfully replicated the spider silk using two interesting components: the silk genome and bacteria.
The spider's silk is a highly valuable material for a reason. It is one of the strongest natural materials in the world. It is thinner than a human hair, but its strength is more than that of steel pound for pound.
Despite the strength, it is flexible and stretchable, making it a potential material for a variety of applications. These include creating robotic muscles, bulletproof vests, and even spacesuits.
There are problems, however. Spiders can only do so much, so the supply is limited. Worse, grouping spiders is not a good idea, as they tend to eat one another.
The team then turned their attention to using microbes.
Microbes Make The Best Material
This isn't the first time scientists attempted to reproduce spider silk through other means. In 2017, European researchers were able to produce artificial spider silk by manipulating the pH gradient.
Others tried to edit the genes by implanting them on yeast, goat's milk, and bacteria. They all failed since the spider's silk gene sequence is long. The material itself will either chop it off or reject it.
The U.S. researchers went on to use microbes for testing, but they modified the process of gene editing.
First, they broke down the gene sequence into smaller parts and introduced each to the E. coli bacteria. This way, the risks of rejection decreased. The microorganism was also likely to follow the genetic instruction correctly.
Then in between the sequence, they added split inteins, which were genetic sequences that served as glue tags. They could also cut themselves off to create an intact protein.
Impressive Results
"When spun into fibers, the microbially produced spider silk had all of the properties of natural spider silk, including exceptional strength, toughness and stretchability," said American Chemical Society in their press release.
The tensile strength was 1.03 gigapascals, which was close to that of the natural spider silk. The engineered material was also tougher at 114 megajoules and stretches up to 18 percent. This makes it also comparable to the natural one.
Most of all, the researchers produced more silk from farm spiders, yielding as much as 2 grams for each liter of bacterial culture.
Improving The Technique
The technique will also serve as the foundation for other possible future projects. For example, they may be able to create underwater adhesives by simply replacing the spider silk proteins with those of mussels.
For now, they are working on stimulating the protein-joining process to occur inside the bacterial cells than having to break the microbe open.
Since the project is partly funded by NASA, the system may play a role during space missions.
"They're currently developing technologies in which they can convert carbon dioxide into carbohydrates that could be used as food for the microbes that we're engineering. That way, astronauts could produce these protein-based materials in space without bringing a large amount of feedstocks," said Fuzhong Zhang, Ph.D., principal investigator.
The result discussion will be part of the Spring 2019 National Meeting & Exposition by ACS.
