When Chinese giant salamanders are injured, they discharge white mucus from glands on their skin. As new research shows, this sticky salamander goo makes for an excellent medical glue, sealing wounds and encouraging them to heal.
Effectively and safely closing wounds after surgery is critical. Most wounds are closed using sutures or staples, but oftentimes these “mechanical” approaches cause further tissue damage and stress. Alternative sutureless approaches are needed, but they have to be strong, sticky, bio-friendly, low cost, and easy to produce. Some medical glues currently exist, but they’re far from perfect, with limitations including toxicity, poor elasticity, and excessive heat at the site of the injury.
New research published in Advanced Functional Materials shows that the skin secretions of the Chinese giant salamander (Andrias davidianus) can be used to produce a medical adhesive for wound healing. In a series of tests, the glue was shown to work in pigs and rats, effectively closing wounds and inducing healing. Researchers from Harvard Medical School, Children’s Hospital of Chongqing Medical University, Sichuan University, and several other institutions contributed to the new paper.
Chinese giant salamander. (Image: Robert Murphy)
Growing over 5.9 feet (1.8 metres) in length and weighing more than 140 pounds (64 kg), the Chinese giant salamander is the largest amphibian in the world. These creatures are regarded as living fossils, having emerged over 200 million years ago at the dawn of the Jurassic. Millions of years of evolution has equipped this giant amphibian with a unique healing strategy; after enduring a scrape or other injury, it excretes a white mucus from glands on its skin, which assists with the healing process.
According to historical accounts, and as noted in the new paper, people in China have been using these skin secretions to treat injuries, such as burns, for over 1,600 years. Indeed, a 2015 study found that the mucus contains many desirable properties, such as compounds that trigger tissue regeneration and an immune defence response.
The researchers have aptly named their new medical adhesive “skin secretion of Andrias davidianus,” or simply SSAD. To make the bioadhesive, the scientists directly collected secretions from giant salamanders by irritating their skin. Once in freeze-dried powder form, a gel-like substance was created by adding a saline solution. Essentially nothing extraneous was added to the salamander mucus, according to the authors.
Images showing the production process, from collecting the mucus from giant salamanders (A,B), through to creating a freeze-dried powder (C), and creating and storing the sticky biogel (D, E). (Image: J. Deng et al., 2019)
Tests on pigs and rats showed that the compound worked well and was nicely flexible. That said, it was slightly less durable than other medical glues. Overall, however, it performed better than commonly used medical adhesives. Using the glue, the scientists were able to close bleeding skin incisions in less than 30 seconds. The compound also contributed to wound healing, resulting in practically no scar formation.
“We anticipate that the low cost, environmentally friendly production, healing-promotion ability, and good biocompatibility of SSAD provide a promising and practical option for sutureless wound closure, as shown by the current research,” concluded the study authors. “SSAD will likely overcome some limitations associated with currently available surgical glues and can perhaps be used to heal wounds on other delicate internal organs and tissues.”
Needless to say, giant salamanders will be needed en masse if this medical glue becomes popular among surgeons and other healthcare practitioners. Statistics provided in the study show that more than 20 million giant salamanders currently exist as livestock in China, as the amphibians are already farmed for use as food and in medicine. Study co-author and Harvard Medical School scientist Yu Shrike Zhang told New Scientist, “You don’t have to kill any animals, you just once in a while very gently scratch their skins to harvest the mucus,” adding that it’s “very sustainable, and you can obtain this adhesive for a long time.”
Despite this large captive population, wild Chinese giant salamanders are listed as critically endangered, as they lose habitat to human activities including mining and logging.
Featured image: Michael Lau/IUCN