Citric Acid-Crosslinked PVA/CMC Composite Membranes with Enhanced Wet-State Stability for Prevention of Postoperative Pericardial Adhesions
Citric acid-crosslinked PVA/CMC composite membranes, particularly the PCC15 formulation, demonstrate enhanced wet-state stability, mechanical integrity, and biocompatibility, effectively preventing postoperative pericardial adhesions in a rabbit model.
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After a heart surgery, the body's natural healing process can sometimes work too well. When the protective sac around the heart, known as the pericardium, is cut or rubbed during an operation, it often tries to heal by sticking to nearby tissues, like the breastbone or the chest wall. These sticky connections, called adhesions, are dense and tough. If a patient needs a second heart surgery years later, these adhesions can hide the clear paths surgeons need to see, making the procedure much harder and riskier. To prevent this, doctors use thin, flexible sheets placed between the heart and the chest wall to act as a temporary shield. However, keeping such a sheet intact is difficult. The heart is constantly moving, beating against the chest, and the sheet is soaked in blood and body fluids. If the material gets too soft, swells up, or falls apart in this wet environment, it stops working as a barrier.
Researchers at Zhengzhou University and Beijing University of Chemical Technology set out to create a better shield. They started with two common materials: poly(vinyl alcohol), a synthetic plastic known for making strong films, and carboxymethyl cellulose, a substance derived from plants that is gentle on the body. While mixing these two made a promising sheet, it was too sensitive to water. When soaked, it would swell up like a sponge and lose its strength, making it unsuitable for the wet, moving environment of the heart. To fix this, the team turned to citric acid, the same compound found in lemons and oranges, to act as a chemical bridge. They treated the mixture with heat, allowing the acid to link the polymer chains together, creating a tighter, more durable network.
The team tested how different amounts of this citric acid changed the behavior of the new sheets. They found that adding more acid made the material much more resistant to water. Without the acid, the sheet absorbed a massive amount of water and swelled up significantly, losing nearly half of its weight after a month in a saltwater solution that mimics the body. As they increased the acid content, the sheets absorbed far less water, swelled much less, and held onto their mass better. The best version, which contained the highest amount of acid tested, still swelled by 93% and lost about 34% of its mass after a month, but this was a significant improvement over the untreated version, allowing it to retain its shape and strength far more effectively.
This resistance to water also meant the material stayed strong when wet. In a dry state, the sheets were already tough, but once soaked, the untreated version became very weak, losing most of its ability to stretch without breaking. The best version, however, remained remarkably strong even when fully saturated. It could stretch to nearly twice its original length without snapping, a flexibility that is crucial for a material sitting on a beating heart. This specific formulation was strong enough to match the natural strength of human heart tissue while remaining flexible enough to move with it.
The researchers then checked if the material was safe for the body. They exposed rat red blood cells to the sheets and found that very few cells were damaged, indicating the material would not cause bleeding issues. They also tested how mouse cells reacted to extracts from the sheets, and the cells remained healthy and active. Furthermore, when they placed fibroblasts, the cells responsible for building scar tissue, directly onto the sheets, the cells did not stick to the surface as readily as they did to standard plastic dishes. This lack of attachment is a good sign, as it suggests the material would not encourage the formation of new scar tissue that could lead to adhesions.
To see if the material worked in a living system, the team used a rabbit model. They created a small injury on the heart surface of the rabbits to simulate surgical trauma. One group of rabbits received the new citric acid-treated sheet over the injury, while another group received no treatment. After thirty days, the rabbits without the sheet had developed severe, tough adhesions between the heart and the chest wall that required sharp tools to separate. In contrast, the rabbits with the sheet had almost no adhesions. The heart moved freely, and the sheet could be peeled away easily. Microscopic examination showed that the treated hearts had far less scar tissue and inflammation than the untreated ones. The study concludes that this simple chemical adjustment creates a flexible, strong, and safe barrier that can effectively prevent the heart from sticking to the chest wall during healing.
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