Natural muscle fibers are made up of spring-like proteins that can contract and stretch without losing their original form, dissipate mechanical energy as heat and maintain incredible tensile strength for all sorts of physical functions. Engineers at Washington University in St. Louis have replicated these proteins using synthetic biology approaches to create a new category of biomaterials for use in medicine, textiles and agriculture.
"Many muscle proteins share similar immunoglobulin-like structures while bearing diverse amino acid sequences. These natural materials provide great inspiration for designing the next generation of protein-based materials," said Fuzhong Zhang, the Francis F. Ahmann Professor in energy, environmental and chemical engineering at the McKelvey School of Engineering and co-director of the WashU Synthetic Biology Manufacturing of Advanced Materials Research Center.
Zhang and his team, including PhD student and first author Shri Venkatesh Subramani, have published results of the fiber fabrication in the journal Advanced Functional Materials.
Subramani explained that nature has evolved numerous protein materials, like silk, collagen and muscle. These materials are useful, yet they are notoriously difficult to manufacture at scale. So Zhang's lab takes a synthetic biology approach, growing genetically modified microbes in bioreactors to produce protein-based materials.
Researchers at WashU have created protein fibers inspired by various animal muscle proteins. These materials are grown in bioreactors and can be stronger than many synthetic fibers, making them ideal for active wear and biomedical implants.
In this case, the team created various muscle proteins in bioreactors and turned them into strong threads unlike any other. Working in collaboration with Sinan Keten at Northwestern University, the team then used these muscle-inspired fibers to understand the design rules that can lead to an ideal material product.
The team found that fibers derived from the filamin protein showed a combination of high tensile strength, toughness, damping capacity, shape recovery and remarkable mechanical stability under high humidity and high heat conditions. "The more hydrophobic the structure is, the better fiber properties you get," Subramani said.
The fiber is superior to the current roster of protein-based materials in that it does not shrink much under high humidity, a problem that limits the application of many spider silk-based materials.
The process of producing the protein is also more stable and provides higher yields because of the greater variety of amino acids it includes, compared to other protein-based materials, Subramani noted. "That's one limitation of existing materials that we've solved," he said.
There are many possible applications for these new fibers. The next step for the research is to scale up production and evaluate potential in different markets, Subramani said. The researchers believe the fibers could be very valuable for use in designing active wear, biomedical implants and tissue scaffolds — and even for creating "fake meat."
"These are just regular muscle proteins that have the same processes as animal muscle," Subramani said. "It can be processed into a meat-like structure."
S.V. Subramani, Q. Guo, H. Gao, et al. "Muscle-Inspired Fibers from Immunoglobulin Domains Combine Superior Mechanical Performance, Energy Damping, and Shape Memory Properties." Advanced Functional Materials (2026): e29451. https://doi.org/10.1002/adfm.202529451
This work is funded by the United States National Science Foundation (award numbers DMR-2207879 to FZ and OIA-2219142 to FZ and SK).
