Researchers have found a way to make a muscle protein and spin it into incredibly strong fibers.
Their synthetic chemistry approach allowed them to polymerize proteins inside of engineered microbes, which then produced the high molecular weight muscle protein, titin.
In the future, such material could be used for clothing, or even for protective gear.
“Its production can be cheap and scalable. It may enable many applications that people had previously thought about, but with natural muscle fibers,” says Fuzhong Zhang, professor in the energy, environmental, and chemical engineering department at Washington University in St. Louis. Now, these applications may come to fruition without the need for actual animal tissues.
The synthetic muscle protein produced in Zhang’s lab is titin, one of the three major protein components of muscle tissue. Critical to its mechanical properties is the large molecular size of titin.
“It’s the largest known protein in nature,” says Cameron Sargent, a PhD student in the division of biological and biomedical sciences and a first author of the paper along with Christopher Bowen, a recent PhD graduate of the energy, environmental, and chemical engineering department.
Muscle fibers have been of interest for a long time, Zhang says. Researchers have been trying to design materials with similar properties to muscles for various applications, such as in soft robotics.
“We wondered, ‘Why don’t we just directly make synthetic muscles?'” he says. “But we’re not going to harvest them from animals—we’ll use microbes to do it.”
To circumvent some of the issues that typically prevent bacteria from producing large proteins, the research team engineered bacteria to piece together smaller segments of the protein into ultra-high molecular weight polymers around two megadaltons in size—about 50 times the size of an average bacterial protein. They then used a wet-spinning process to convert the proteins into fibers that were around 10 microns in diameter, or a tenth the thickness of human hair.
The researchers then analyzed the structure of these fibers to identify the molecular mechanisms that enable their unique combination of exceptional toughness, strength, and damping capacity, or the ability to dissipate mechanical energy as heat.
Aside from fancy clothes or protective armor (again, the fibers are tougher than Kevlar, the material used in bulletproof vests), Sargent points out that this material has many potential biomedical applications as well. Because it’s nearly identical to the proteins found in muscle tissue, this synthetic material is presumably biocompatible and could therefore be a great material for sutures, tissue engineering, and so on.
Zhang’s research team doesn’t intend to stop with synthetic muscle fiber. The future will likely hold more unique materials enabled by their microbial synthesis strategy. Working with Bowen, Sargent, and Zhan, Washington University has filed a patent application based on the research.
“The beauty of the system is that it’s really a platform that can be applied anywhere,” Sargent says. “We can take proteins from different natural contexts, then put them into this platform for polymerization and create larger, longer proteins for various material applications with a greater sustainability.”
The research appears in the journal Nature Communications. Additional researchers from Washington University in St. Louis and Northwestern University contributed to the work.
The research received support from the Office of Naval Research and an Early Career Faculty grant from NASA’s Space Technology Research Grants Program. Use of BioCARS was also supported by the National Institutes of Health, National Institute of General Medical Sciences.
