Slug slime inspires surgical glue that sticks to wet surfaces
Image credit: Wyss Institute
The slimy trail left by everybody’s least favourite gastropod has served as the inspiration for a new family of adhesives: tough adhesives. These are non-toxic, flexible, shock-absorbent and can be stuck to wet surfaces.
Binding to wet surfaces has proved a headache to materials scientists and surgeons. While some surgical glues exist, these fail under wet conditions, such as inside the body. With few other options available, surgeons tend to resort to using stitches and staples to seal internal wounds.
A team of researchers based at Harvard University’s Wyss Institute for Biologically Inspired Engineering turned to slug slime for a solution. Slugs and snails secret different types of mucus to help them slide across rough surfaces without damaging their bodies. Their ‘foot mucus’, which is used for crawling on, has glue-like and lubricant properties.
The researchers focused on the Dusky Arion, an unassuming-looking brown slug capable of sticking to damp surfaces.
Previously, it has been revealed that the strength of this slug’s ‘glue’ is due to positively charged proteins within a negatively charged matrix. On the basis of this discovery, the researchers developed a new type of adhesive. Tough adhesives are made up of charged proteins suspended in a hydrogel; this heavily water-based material has many potential medical applications due to its ability to stretch and adjust to moving bodily parts. The charged proteins are attracted to slightly negatively-charged cells. Covalent bonds form between the molecules, allowing the proteins to permeate the skin.
As well as being flexible and biocompatible, the glue has proved tough. The addition of calcium ions, which form ionic bonds with the hydrogel, renders it highly shock-absorbent. Under stress, these ionic bonds are first to break, allowing the glue to absorb energy.
In a demonstration, the researchers used a tough adhesive to seal a large hole in a beating pig’s heart. The patch adhered to the bloody surface, and did not leak, even after thousands of pumps. The team also used the surgical glue to stem bleeding from a rat’s liver.
Other applications, according to the researchers, could be to fix cartilage discs, or even as everyday plasters to close external wounds.