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Spray-On Hydrogel Reduces Heart Surgery Scar Tissue


(Sasin Tipchai, Pixabay)

8 Aug. 2019. A biocompatible polymer gel, sprayed on the hearts of lab animals, reduces the severity of scar tissue that can build up after cardiac surgery. A team of medical researchers and materials scientists from Stanford University in California describe the spray-on gel and its tests in yesterday’s issue of the journal Nature Biomedical Engineering (paid subscription required).

Researchers from the labs of biomaterials and engineering professor Eric Appel and cardiac surgery professor Joseph Woo are seeking better options for controlling the growth of scar tissue, known as adhesions, following surgery. While some post-surgical adhesions are considered normal, they can be troublesome for cardiac patients, particularly those who need follow-up surgery. In these heart patients, surgeons need to first remove the built-up scar tissue from the heart, which increases the risk of further injury to the heart or lungs, and lengthens the amount of time in surgery for the patient. While some treatments to prevent adhesions are commercially available, the researchers say the treatments’ results are uneven and thus not often used.

Appel’s biomaterials lab studies hydrogels for drug delivery. Hydrogels are water-based biocompatible polymers with a chemical structure that in some cases can change form after they’re applied. Doctoral student and first author Lyndsay Stapleton is developing an injectable hydrogel with nanoscale particles to reduce tissue damage, and altered the gel’s viscosity and flow properties to work as a spray.

When sprayed on the hearts of lab rats undergoing surgery to repair induced heart attacks, the hydrogel remained on the hearts and prevented adhesions from forming. Stapelton and colleagues prepared five hydrogels with a range of properties and tested the gels on simulated heart surgeries in lab rats, as well as currently available adhesion-prevention products. The results show the original gel formula the team code-named PNP 1:10 completely prevents adhesions from forming after four weeks, while the other hydrogels had varying success. The researchers say the commercially-available products did not reduce any adhesions in the rats.

The team then tested PNP 1:10 in sheep — animals with hearts similar in size to humans — induced with heart disease and undergoing coronary bypass surgery. The results with sheep were similar to rats, with spray-on PNP 1:10 reducing adhesions in the animal hearts. PNP 1:10, say the researchers, is made with materials already approved by FDA for other products, and the animals do not show adverse effects from its use. After two weeks, the hydrogel dissolves and is absorbed into the body.

The researchers say the PNP 1:10 formula gives the hydrogel enough viscosity to cover the organs, yet remain attached and not impair their functioning. “The gel doesn’t prevent tissues from moving around,” says Appel in a university statement. “It simply provides a physical barrier to keep them from sticking to each other.” Woo adds, ““It covers all of the irregular surfaces of the heart, adhering to the tissues, but not to itself.”

The team is further developing PNP 1:10 to prevent surgical adhesions in other organs. They next plan to test the hydrogel spray in lab rats undergoing abdominal surgery.

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