For people living with heart valve disease, medical devices such as heart valves and stents are critical in saving lives. These implants face constant pressure within the human body, with heart valves working under high pressure to pump blood, opening and closing hundreds of millions of times over a span of ten years. Proteins in the blood can accumulate on the surfaces of these implants, gradually forming blood clots. This often necessitates invasive surgery to either replace or remove the implant. In response to this challenge, scientists are exploring the use of a common macromolecule found in human cells to create materials that could prevent blood clots from forming in medical devices and implants.

Zwitterions, a type of macromolecule present in human cells, are unique in that they carry both positive and negative charges simultaneously, making them neutral overall. The term ‘Zwitter’ comes from the German word for ‘hybrid,’ reflecting this dual-charge characteristic. These molecules are highly effective at forming bonds with water molecules. Zwitterions are already naturally occurring in cell membranes, where they help to create a thin layer of water, ensuring that blood and other proteins flow smoothly through the heart and organs without sticking to surfaces. Drawing on the zwitterion's ability to attract water while remaining chemically neutral, researchers at the University of Sydney (Sydney, Australia) have developed a zwitterionic coating that binds with water to create a thin watery layer. Inspired by the natural properties of cell membranes, the research team is working to replicate this function to design materials that could prolong the lifespan of medical implants.

So far, the team has created a zwitterionic coating that, when applied to material surfaces, forms a thin layer of water just a few nanometers thick, essentially creating a protective watery "armor." In contrast, materials without the coating repel and spread water away from the surface. The researchers are now focusing on developing new formulations that can be chemically bonded to the surface of various types of implants, whether made from tissue, metal, plastic, or rubber. The goal is to minimize their interaction with blood, thereby preventing clot formation. The team has published a detailed review in Cell Biomaterials, outlining the potential applications of zwitterions in biomedicine and providing a comprehensive blueprint for designing surface coating technologies.

By using Zwitterion-coated materials, we aim to decrease the risk of blood clots and increase the lifespan of heart valves and other medical implants,” said Dr Sina Naficy, who is leading the research team developing heart valves that are more resistant to blood clots.

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