Whether or not to perform foetal surgery is a heart-wrenching decision. This type of surgery involves penetrating the highly delicate amniotic sac, increasing health risks to the foetus. Now researchers report the development of a glue, inspired by the tenacious grip of mussels on slippery rocks, that could one day help save the lives of the youngest patients.
“One of the biggest risks in performing surgery on foetuses is not the surgical procedure itself, but the insertion of a foetal scope through the amniotic sac, which is very fragile,” Diederik Balkenende says. “After the surgery, the small hole where the scope penetrated the membrane can start to tear. If it tears completely, premature labour is likely. Because these operations are often done in the second trimester well before the foetus is fully developed, early delivery increases the risk of foetal morbidity. An adhesive that can prevent the amniotic sac from tearing could help the foetus remain in the womb longer, which would potentially lead to a healthier future for the baby.”
A well-known example of a severe birth defect that would make a foetus a candidate for surgery is spina bifida.
To fix such problems a few decades ago, surgeons had to cut open a woman’s abdomen and womb. Now, doctors can use skinny endoscopic tools to perform operations through a small hole. Still, to reach the fetus, the instruments must penetrate the amniotic sac, which cannot heal or easily be sewn shut because it is so fragile. Sealing it with an adhesive is a challenge because the membrane is wet; additionally, delivering a surgical glue post-operation is a major hurdle.
Balkenende, a postdoctoral researcher in the lab of Philip Messersmith at the University of California, Berkeley, wanted to eliminate the crosslinkers. So he infused an adhesive ingredient from the mussel foot called dihydroxyphenylalanine, or DOPA, into a special polymer that can dissolve in a biocompatible solvent. The solution can then be drawn into a syringe.
To test their material, the researchers used pieces of a membrane that surrounds a cow’s heart as a model of the amniotic sac. They applied the solution with the syringe to overlapping pieces of the wet, filmy tissues. On contact with moisture on the tissues, the mixture immediately became rubbery. After about an hour, the glue set and held the pieces together.
But even with the right polymer and solvent, the researchers still needed to figure out how the solution might work in a real surgery.
“Repairing a hole in the amniotic sac is a daunting engineering challenge,” 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.”
Getting the adhesive into clinical practice will take additional work. The researchers are still perfecting their glue and examining biocompatibility. Preclinical testing in animals also has to be completed, Balkenende says.