In Jan 2017, 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. 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.
Synthetic hagfish slime may be used for ballistics protection, firefighting, anti-fouling, diver protection, or anti-shark spray.
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.
The hagfish has proven adept at evading larger predators such as marine mammals, sharks and cephalopods (octopus, squid). In less than a second, a stressed hagfish can emit a coiled thread—known as a skein—which contains mucins and fine fibers. Once ejected, the skein rapidly expands when mixed with seawater. According to research conducted by Dr. Douglas Fudge and his colleagues at the University of British Columbia’s Department of Zoology, the completed slime is comprised of 99.996 percent seawater, with the remaining components being the mucins (0.0015 percent) and fiber threads (0.002 percent). It’s considered to be 1,000 times more dilute than other known animal mucus secretions. Once the skeins are introduced into seawater, the material expands approximately 10,000 times in a matter of milliseconds.
The mucin-fiber thread substance only accounts for approximately three to four percent of the fish’s body mass. To discharge the material, the hagfish has 90 to 200 slime pores running along each side of its body. When attacked, the animal has the capability to eject slime through a selective grouping of pores which are closest to the predator, or specifically within the attacker’s mouth.
The hagfish is the only known animal that secretes fully formed intermediate filaments. While the hagfish filaments are often compared to spider silk, the spider spins silk from a liquid precursor,” he says. “Since the hagfish filament is preformed inside specialized cells along the body, the release of the filaments and mucin causes the slime to be formed instantaneously. This instantaneous expansion was another unique material property that intrigued us as other super absorbing materials usually take minutes to fully hydrate.”
Following the initial study on the naturally-produced material, the research team began to explore ways in which hagfish slime could be synthetically reproduced for Navy use. After roughly six months of research, the scientists introduced alpha and gamma proteins drawn from the Pacific hagfish to the Escherichia coli bacteria—commonly known as E.coli. Alpha proteins are a key plasma or blood protein that binds to copper, nickel, fatty acids and other materials; and gamma proteins fall under a class of spherical, globe-like proteins which respond to antigen stimulation by forming into the common form of immunoglobins (i.e. antibodies). The proteins were retrieved from the bacteria and runthrough a series of isolation and purification processes. Following those steps, the proteins would ultimately be combined together, swiftly joined into a crosslinked solution via centrifuge.
In terms of ballistics protection, the Navy could pursue the hypothesis posed by Dr. Fudge— now with Chapman University—that hagfish filament could serve as a renewable source capable of replacing synthetic, petroleum-based materials. With petroleum being a key component in Kevlar, a material commonly used in military combat helmets and ballistic vests, there is potential for synthetically-produced hagfish slime to be used in the development of innovative protective equipment.
Firefighting applications may be feasible based on the slime’s ability to absorb and retain water. Synthetic slime with the same properties might be useful as a fire suppressant.
Due to the slick nature of the slime, it may also hold promise for antifouling technology on Navy ships. Anti-fouling refers to materials and coatings used to prevent biofouling, the buildup of microorganisms, animals and vegetation on wet surfaces. The accumulation of barnacles, seaweed, mollusks and other stowaways on a hull can add weight and increase drag, which can result in up to a 10 percent speed reduction. Biofouling can also impact fuel efficiency and potentially increase greenhouse gas emissions.