Slimy hagfish inspire 'super hydrogels'

The unusual secretions of the Atlantic hagfish are being studied by scientists who want to harness the viscous and elastic properties of the creature's slime for human use. When attacked or threatened by a predator the marine creature defends itself by secreting a milky-white substance from its glands. This instantly reacts with the seawater around it to form a mass of slime that clogs the mouth and gills of the would-be attacker. But this slime has special properties that could benefit mankind, according to scientists from ETH Zurich (Swiss Federal institute of Technology). Hagfish slime is an extremely diluted hydrogel, consisting of over 99.99 percent water. Hydrogels are used in a multitude of everyday products including diapers, moisturisers and contact lenses. But hagfish slime is more efficient and fast-forming than other types of hydrogel, such as conventional animal gelatin. "Hydrogels are present in many everyday products; from diapers to face creams to food materials. And by studying the slime, we're trying to find out how we can make super hydrogels, so hydrogels that can entrap large amounts of water," said PhD student Lukas Böni. The glandular secretion the hagfish produces when attacked is made from mucin vesicles and tightly coiled skeins of protein measuring just 150 micrometres in diameter. When released by the hagfish they quickly interact with seawater; the mucin vesicles releasing a saliva-like substance and the skeins unwinding into long threads. Together they form a matrix of slime that can disable much bigger marine animals. How the coiled thread unwinds with such speed and efficiency when it comes into contact with seawater is still a mystery the team is working to understand. "One protein thread is coiled up into one skein, and if you extend this thread it is up to 30 centimetres long. And when these skeins come into contact with water they unravel and form these long protein threads, which span a network that together with the mucin entraps the water," said postdoctoral researcher Patrick Rühs, adding that the protein threads have a similar property to spider silk and are extremely tear-resistant and elastic. The researchers travelled to Norway to collect samples of the hagfish's secretion before transporting it back to their laboratory in Zurich. "We bring in the fish, we sedate them, we blot them dry. And once they're sedated we put them on a dissection tray and then we mildly stimulate the ventral side of the fish. This causes the muscles to contract and the exudate, this glandular secrete, to be expelled," said Böni, adding: "After the sampling the fish wakes up again; so the fish is not harmed by taking the sample." They are now working to unlock the secret of the slime formation and its huge capacity to absorb water with the hope of recreating it artificially in the lab. Böni believes that the hagfish's natural system is far too complex to completely replicate, but is hopeful they can develop a gel that follows the principle of the natural slime. Similar research from the University of Guelph in Canada has proposed that the fibres of the hagfish slime could be used to make textiles.