GoKawiilNatural blood clots, which include platelets (light blue clumps) and red blood cells in a fibrin mesh, can take minutes to form.Credit: Anne Weston, EM STP, The Francis Crick Institute/Science Photo Library
Red blood cells modified with Nobel-prizewinning chemistry can snap together to form clots that staunch bleeding in seconds. That’s according to a study, published on 29 April in Nature1, that tested the technology in rats.
The method, called click clotting, produces clots that are stronger than either natural clots or a commercial product used to stop bleeding. If shown to be safe and effective in people, the approach could provide a rapid way to induce haemostatis, the body’s natural process for controlling bleeding, and to stem potentially deadly blood loss during surgery or after injuries.
“It’s really cool,” says Ashley Brown, a biomedical engineer jointly at the University of North Carolina in Chapel Hill and North Carolina State University in Raleigh, who was not involved in the study. “Particularly in emergency medicine, there’s a large need for materials that can be easily transported and rapidly induce haemostasis.”
Thinking outside the clot
The engineered clots are unusual: red blood cells are not primarily responsible for initiating natural blood clots. Instead, specialized cells called platelets, working with other coagulation factors, seed a clot by sticking to blood-vessel walls and forming a plug. Many efforts to develop artificial blood clots have focused on mimicking platelets.
This tiny device spins blood clots away
But Jianyu Li at McGill University in Montreal, Canada, trained his mechanical engineer’s eye on natural clots and found them lacking. “They are mechanically very weak, and easy to rupture and detach, causing re-bleeding,” Li says. They are also slow to form — taking minutes — which is a delay that can spell the difference between life and death on the operating table or in the emergency department.
So, the researchers looked at the clot environment and decided to focus on an abundant alternative to platelets: the red blood cell. If they could cross-link red blood cells together, Li reasoned, they could harness the cells’ elasticity and durability. Red blood cells can circulate through the body for months.
To modify the cells, Li and his team relied on ‘click chemistry’, a suite of reactions that snap two molecules together like the ends of a seat belt, and are remarkably quick, simple and clean. The application of click chemistry in a biological system is often called bioorthogonal chemistry, because the reactions do not perturb the usual functioning of cells.
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