A team of U.S. Navy scientists and engineers at Naval Surface Warfare Center, Panama City Division (NSWC PCD) have successfully recreated a natural material used for marine wildlife defense to assist military personnel.
Biochemist Dr. Josh Kogot and Materials Engineer Dr. Ryan Kincer have produced a synthetic component of hagfish slime from the alpha and gamma proteins of the Pacific hagfish.
The Pacific hagfish, also known as slime eels, are bottom-dwelling scavengers which live on the ocean floor. The hagfish can secrete slime to protect themselves by obstructing the gills of predators which come into contact with the slime.
According to Kincer, hagfish slime consists of two protein-based components — a thread and a mucin.
“The coiled up thread behaves like a spring and quickly unravels upon contact with water due to stored energy,” said Kincer. “The mucin binds to water and constrains the flow between the micro channels created by the thread dispersion. The interaction between the thread, mucin, and seawater creates a three-dimensional, viscoelastic network. Over time, the thread begins to collapse on itself, causing the slime to slowly dissipate. Studies have shown the hagfish secretion can expand up to 10,000 times its initial volume.”
The hagfish slime thread has been compared to spider silk. Both are natural, renewable materials which could one day replace synthetic products derived from petroleum-based precursors. Kogot said the slime thread has comparable mechanical properties to Kevlar, a synthetic fiber used as a reinforcing agent for rubber products and protective gear.
During synthetic recreation, alpha and gamma proteins were produced in an Escherichia coli bacteria, or E.coli, where each protein was recovered from the bacteria after a series of isolation and purification steps. The alpha and gamma proteins were later combined together and rapidly assembled in a crosslinking solution. A sample of natural and synthetic hagfish threads were compared using a scanning electron microscope to visually confirm the production of the synthetic threads.
The intended use of the synthetic slime is to provide non-lethal and non-kinetic defense to the fleet.
“The synthetic hagfish slime may be used for ballistics protection, firefighting, anti-fouling, diver protection, or anti-shark spray,” said Kogot. “The possibilities are endless. Our goal is to produce a substance that can act as non-lethal and non-kinetic defense to protect the warfighter.”
Kincer said the addition of using a material such as the slime will be valuable to the U.S. Navy.
“Researchers have called the hagfish slime one of the most unique biomaterials known,” said Kincer. “For the U.S. Navy to have its hands on it or a material that acts similar would be beneficial. From a tactical standpoint, it would be interesting to have a material that can change the properties of the water at dilute concentrations in a matter of seconds.”
The effort to create new synthetic means to behave like the natural hagfish slime is supported by Navy Innovative Science and Engineering (NISE) funding and the Office of Naval Research Code 32, ocean battlespace sensing department. The team is researching ways to increase the slime’s surface attachment capability, potential delivery systems, and enhanced stability in various environments. From there, Kogot and Kincer will continue to look for innovative applications and explore different variations and properties of the material.
They are currently working to increase the slime protein scale and improve protein assembly.
By Katherine Mapp, Naval Surface Warfare Center, Panama City Division Office of Congressional and Public Affairs