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Text: Angelika Jacobs

In the event of a serious injury, the body can hardly stop the bleeding itself. Artificial molecules are said to help improve blood clotting.

An accident. Severe blood loss. Things have to be done quickly in the emergency room. The body copes well with small injuries: With blood clotting, it has a sophisticated system for closing wounds. If the bleeding is profuse, however, the organism is unable to provide sufficient coagulation factors at the crucial location. A clot of blood cannot form to stop the flow of blood. Medical staff can help with clotting factors that are isolated from donated blood and given in an emergency. "However, isolating these factors is expensive, they do not last long and are not particularly efficient," says Michael Nash.

With his research team, the professor of molecular engineering is developing smart molecules that can latch into the body's own coagulation mechanism. The aim is to strengthen the blood clot in order to close an injury faster and more stably - not only in severe wounds, but also in hereditary coagulation disorders or if the use of blood-thinning medication inhibits coagulation.

Platelets and fiber network

If a wound bleeds, the blood flow changes, and this mechanical stimulus gives the platelets the signal to collect at the injured site. The platelets in turn release a messenger substance that stimulates the formation of a network of so-called fibrin fibers. Platelets and fibrin network combine to form a blood plug that closes the wound.

“This plug has interesting mechanical properties: the more tension is exerted on it, the stiffer it becomes,” says Nash. This is in contrast to the everyday experience that an elastic object such as a tension spring loses its structure if it is stressed too much: the spring breaks irreversibly and can no longer contract or expand elastically. The blood clot, on the other hand, becomes more stable, so to speak, the stronger the forces that the blood exerts on it.

Nash's team wants to strengthen these special characteristics. To do this, they work with macromolecules, which consist of elastic protein building block chains. Experts call them "elastin-like polypeptides" (ELPs). As part of a project funded by the European Research Council ERC, Nash's research group has further developed these ELPs so that the body's own coagulation factors recognize them at the site of the injury and incorporate them into the fibrin network.

Like oil in water

But that's not all: With another trick, these molecules further improve coagulation. Due to their special design, the ELPs change their properties when a certain temperature threshold is exceeded. They are water-soluble at room temperature and can therefore be easily stored for later use. However, at an ambient temperature of around 37 degrees, they become hydrophobic: like oil in water that collects in droplets, the ELPs agglomerate to form nanoparticles, which allows them to circulate in the blood longer and remain stable. In addition, this strong accumulation of ELPs in nanoparticles promotes their chemical crosslinking with the fibrin fibers.

In laboratory tests, Nash and his colleagues were able to observe that these special properties of the designed macromolecules lead to the blood clot having a thinner, but at the same time denser and stiffer network, which makes it more stable. In addition, the modified clot is broken down more slowly by the body's enzymes, which could improve wound healing in certain cases. In the meantime the development has been registered for a patent; now preclinical studies on laboratory animals are to follow.

Mechanical feelers

What the researchers are researching and developing in the context of blood coagulation is embedded in a larger topic: the stability of macromolecules, as they are increasingly used in medicine; mostly antibodies and enzymes. In addition to designing macromolecules as potential therapeutics, the team is also researching natural phenomena that could serve as inspiration for the properties of these new molecules. The focus is on reactions to mechanical stimuli, such as the aforementioned signal for the start of blood clotting. “How exactly proteins perceive and process mechanical stimuli is a field that has not yet been explored,” says Nash.

In the world of proteins, for example, there are mechanisms by which a protein “clings” to an object to which it binds under tensile force. The Basel research team was recently able to describe such a mechanism in intestinal bacteria that can cling to cellulose fibers despite the strong shear forces in the digestive tract.

Such tricks from nature could possibly also be built into biopharmaceuticals, which then react to mechanical stimuli and, for example, change the way they work. Such properties would be useful, for example, for nanoparticles that should cling to tumors despite strong blood flow. “Designing biomolecules in such a way that they adhere specifically to certain structures, tissues or cells: That will be the key to developing targeted therapies that only work where they are needed, but protect the rest of the organism,” concludes Nash. "We are excited to see where our approach will lead us."

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