If you’ve ever tried to pull a mussel off a rock, you’ll know that the task is a lot harder than it appears.
The ability of the shellfish to adhere firmly to its base while surrounded and buffeted by water has long been noted. So too has the obvious subsequent thought: if the same level of efficient wet adhesion could be duplicated in a surgical context, then certain operations that are currently very dangerous would become a great deal safer.
Prime among these is surgery conducted on fetuses to address heart or spinal abnormalities. Under current circumstances, the surgery itself – although of course involving minuscule endoscopic procedures – is relatively safe.
The danger arises because in order to gain access to the foetus, a surgeon must first penetrate the amniotic sac, the tough transparent pair of membranes that enclose the developing baby in protective fluid.
After being breached during surgery, the sac often fails to heal properly, resulting in a structural weakness that can lead to tearing, infection and even premature labour.
This is where the mussels come in. The fact that mussel adhesive strength is derived from the presence of an amino acid called dihydroxyphenylalanine (DOPA) has been known since at least 1981.
However, attempts to adapt it for use in humans have been challenging. To do so requires incorporating it into a hydrogel. In most experimental cases, this has required the addition of oxidative cross-linkers, which damage biological tissues.
Other approaches have avoided the problem, but the results, while bio-friendly, have weakened the DOPA’s stickiness.
Now, a team led by Diederik Balkenende from the Messersmith Research Laboratory at the University of California Berkeley has succeeded in incorporating DOPA into a non-toxic medium without loss of strength.
To do so, Balkenende and colleagues mixed the adhesive with a newly created polymer that dissolves into a biocompatible solvent. The substance is liquid enough to be administered using a syringe.
As proof of concept the researchers tested it on a ruptured cow’s heart and found that after an hour the overlapping wet tissues were stuck firmly together.
Despite this success, however, the researchers acknowledge that the novel glue by itself is not enough to guarantee successful repair of a human amniotic sac.
To achieve this, they say, there will need to be changes made to operating procedure. In particular, the mussel glue will need to be applied in two stages – the first before the amniotic sac is penetrated.
“Repairing a hole in the amniotic sac is a daunting engineering challenge,” lab boss Philip Messersmith says.
“So in addition to the novel polymer that we’re making, we’re approaching its delivery from a new angle, which is what we call pre-sealing. Injecting the liquid polymer between the inner wall of the uterus and the amniotic sac and letting it harden before surgery could provide the mechanical support needed to prevent the hole from tearing and causing a catastrophic rupture.”
Balkenende will present his research at the 254th National Meeting & Exposition of the American Chemical Society (ACS).