Dual-function hydrogel implant helps stop endometriosis, pregnancy

A novel, stimuli-responsive hydrogel implant for reversible occlusion of the fallopian tubes holds promise for preventing pregnancy and endometriosis or halting the latter’s spread, as reported in a study.

Developed by researchers from ETH Zurich and the Swiss Federal Laboratories for Materials Science and Technology (Empa), the implants leverage the swelling ability of hydrogels to achieve gentle and reversible but highly effective tubal occlusion, noted lead author Dr Alexandre Anthis from ETH Zurich, Zurich, Switzerland.

Initially, the implant measures approximately 2 mm in length. However, upon insertion into the fallopian tubes via a minimally invasive hysteroscopic procedure, the hydrogel comes into contact with bodily fluids and significantly swells. This results in a substantial increase in size, effectively blocking both sperm and menstrual blood from passing through the tubes. The hydrogels can withstand pressures up to 255–558 mm Hg, well above the typical abdominal pressure of 95 mm Hg. [Adv Mater 2024;36:e2310301]

Endometriosis is believed to occur when blood shed during menstruation, which contains cells from the uterine lining, flows back into the abdominal cavity via the fallopian tubes, Anthis pointed out. These cells, he added, can subsequently settle in the abdominal cavity, leading to inflammation, pain, and the formation of scar tissue.

Stable

“We discovered that the implant had to be made of an extremely soft gel—similar in consistency to a jelly baby—that does not impact native tissue and is not treated and rejected as a foreign body,” Anthis explained. “We wanted to ensure that the implant was compatible [with the human body] as well as stable.”

Anthis and colleagues first conducted ex-vivo experiments on human and animal fallopian tubes that had for instance been removed in the course of treating ovarian cancer. The implant was found to have low stiffness and negligible cytotoxicity, indicating that the hydrogel poses a low risk of inducing fibrosis and causing cell damage, both of which could lead to decreased fertility and fallopian tube scarring.

In a subsequent experiment, the research team implanted the hydrogel in a live piglet. Histological analysis confirmed that the implant was still in position 3 weeks after the implantation, with no sign of any foreign-body reactions.

Degradable

Another important feature of the hydrogel implant is that it can be removed in a noninvasive or minimally invasive manner.

The hydrogel implant consists of acrylamide-based polymers crosslinked with either poly(ethylene glycol) di-photodegradable acrylate (PEGdiPDA) or N, N'-bis(acryloyl)cystamine (BAC). These crosslinkers impart specific degradation properties to the hydrogels, such that PEGdiPDA hydrogels degrade upon exposure to near-visible UV light, while BAC hydrogels degrade through interaction with glutathione. Both options allow for controlled implant breakdown within a clinically relevant timeframe (ie, 30 min).

“Our hydrogel implant can be easily and quickly destroyed … so that recipients don’t have to have an invasive and risky operation should they decide to reverse the procedure,” said senior study author Prof Inge Herrmann from ETH Zurich.

The next step in the research is to determine how the hydrogel implant will behave long-term once in position in the fallopian tubes, especially when recipients engage in strenuous physical activities like sport.

“So far, very little research has been done at the point where materials science, process engineering, and gynaecology meet. But this is a vitally important area of research. We hope that our work will count as a meaningful step in the right direction,” Hermann said.