Injectable polymer could stem battlefield injuries

University of Washington researchers have developed PolySTAT, a new injectable polymer that strengthens blood clots.

Administered via injection, the polymer is claimed to find any unseen or internal injuries and starts working immediately.

The University said the new polymer – described in Science Translational Medicine – could become a first line of defence in a host of trauma scenarios.

A 3D rendering of fibrin forming a blood clot, with PolySTAT (in blue) binding strands together
A 3D rendering of fibrin forming a blood clot, with PolySTAT (in blue) binding strands together

It has been tested in rats, and the researchers said it could reach human trials in five years.

In the initial study with rats, 100 per cent of animals injected with PolySTAT survived a typically lethal injury to the femoral artery. Only 20 per cent of rats treated with a natural protein that helps blood clot survived.

“Most of the patients who die from bleeding die quickly,” said co-author Dr. Nathan White, an assistant professor of emergency medicine who teamed with UW bioengineers and chemical engineers to develop the macromolecule. “This is something you could potentially put in a syringe inside a backpack and give right away to reduce blood loss and keep people alive long enough to make it to medical care.”

According to a statement, the UW team was inspired by factor XIII, a natural protein found in the body that helps strengthen blood clots.

Normally after an injury, platelets in the blood begin to congregate at the wound and form an initial barrier. Then a network of specialised fibres called fibrin start weaving themselves throughout the clot to reinforce it.

If that scaffolding can’t withstand the pressure of blood pushing against it, the clot breaks apart and the patient keeps bleeding.

Both PolySTAT and factor XIII strengthen clots by binding fibrin strands together and adding cross-links that reinforce the latticework of that natural bandage.

The synthetic PolySTAT offers greater protection against natural enzymes that dissolve blood clots. Those help during the healing process, but they work against doctors trying to keep patients from bleeding to death.

The enzymes, which cut fibrin strands, don’t target the synthetic PolySTAT bonds that are now integrated into the clot. That helps keep the blood clots intact in the critical hours after an injury.

The synthetic polymer offers other advantages over conventional haemorrhaging treatments, said White, who also treats trauma patients at Harborview Medical Center.

Blood products are expensive, need careful storage, and they can grow bacteria or carry infectious diseases, he said. Plus, the hundreds of proteins introduced into a patient’s body during a transfusion can have unintended consequences.

After a traumatic injury, the body also begins to lose a protein that’s critical to forming fibrin. Once those levels drop below a certain threshold, existing treatments stop working and patients are more likely to die.

In the study, researchers found PolySTAT worked to strengthen clots even in cases where those fibrin building blocks were critically low.

The UW team also used a highly specific peptide that only binds to fibrin at the wound site. It does not bind to a precursor of fibrin that circulates throughout the body. That means PolySTAT shouldn’t form dangerous clots that can lead to a stroke or embolism.

The team said next steps include testing on larger animals and additional screening to find out if it binds to any other unintended substances. They also plan to investigate its potential for treating haemophilia and for integration into bandages.