Injectable polymer curbs blood loss by strengthening clots

A 3D rendering of a blood clot forming, with PolySTAT (in blue) binding strands of fibrin together (Image: William Walker/University of Washington)

With uncontrolled bleeding the major cause of deaths on the battlefield, researchers at the University of Washington (UW) have developed an injectable polymer that could stem bleeding and provide extra time to get the injured to medical care. Called PolySTAT, the new polymer stems blood loss by strengthening blood clots.

Current treatments to enhance clotting often involve the use of other people's platelets, which are expensive, need to be refrigerated and have a short shelf life, meaning they aren't always available in the field. Back in 2009, we saw the development of synthetic platelets made from biodegradable polymers that addressed these issues.

The UW researchers have taken a similar approach, but instead of giving a helping hand to platelets, which are responsible for forming the initial plug at the site of an injury, their injectable polymer assists a protein called fibrin, which strengthens the platelet plug.

The team took inspiration from a natural protein found in the body called factor XIII, which helps strengthen blood clots by binding fibrin strands together and reinforcing the latticework of a blood clot through the addition of "cross-links." Its creators say that PolySTAT performs the same function, but offers additional advantages in that natural enzymes that help with the healing process but dissolve blood clots by cutting fibrin strands, don't target the PolySTAT bonds.

Also, the polymer was found to strengthen clots even when the levels of fibrin were critically low. This is important because the body begins to lose a protein critical to the formation of fibrin in the wake of a traumatic injury.

Furthermore, the researchers say that PolySTAT shouldn't form clots in the body that can result in a stroke or embolism as it only binds to fibrin at the site of a wound, ignoring a precursor of fibrin that circulates throughout the body.

In an initial study involving rats, the team found that 100 percent of those injected with PolySTAT survived an injury to the femoral artery that would usually be lethal, compared to a survival rate of only 20 percent in rats treated with a natural protein that helps blood clot.

"Most of the patients who die from bleeding die quickly," said study 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."

In addition to use on the battlefield, the researchers say PolySTAT could become the first line of defense for everything from rural car accidents and search and rescue missions in isolated areas. They will also examine its potential for treating hemophilia and if it could be integrated into bandages.

Before moving onto human trials, which could occur within five years, the researchers will first move onto testing the polymer in larger animals and conduct further screening to see if it binds with any unintended substances.

The team's study appears in the journal Science Translational Medicine.

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