Traumatic injury is the third leading cause of death in the state of Texas, surpassing strokes, Alzheimer's disease and diabetes, according to the Centers for Disease Control and Prevention. A massive number of these deaths are the result of uncontrolled bleeding.
"Severe blood loss can rapidly lead to hemorrhagic shock," said Dr. Akhilesh Gaharwar , a biomedical engineering professor at Texas A&M University. "Many patients die within one to two hours of injury. This critical period is often referred to as the 'golden hour.'"
Thanks to funding from the U.S. Department of Defense and the National Science Foundation, Gaharwar and his fellow researchers in the biomedical engineering department have found a way to extend this golden hour — using clay.
Gaharwar, Dr. Duncan Maitland and Dr. Taylor Ware are developing a suite of injectable hemostatic bandages — biomedical materials that stop bleeding and promote blood to clot faster. Their research is specifically targeting deep internal bleeding where traditional methods like compression are not possible.
Two papers, recently published in Advanced Science and Advanced Functional Materials demonstrate that these dressings can reduce bleeding time by almost 70%.
"Under normal circumstances, human blood clots within six to seven minutes," said Gaharwar. "Using these hemostatic dressings, we are able to reduce the clotting time to one to two minutes."
The goal is a lifesaving device simple enough that a critically injured person could apply it to themselves immediately after injury.
"For a self-applied or in-the-field-applied device, you can't use the fancy mechanics and apparatus that you would have in the operating room," said Ware. "There can't be any special tools. You have to have something that just works and works quickly."
The research hinges on a class of materials that have been used for wound treatment for thousands of years. Certain naturally occurring clay minerals contain silicate-based particles that can accelerate blood coagulation. The exact mechanics of this effect are still an active area of investigation.
"These clay particles were being used as a hemostat in ancient civilizations in China, Mesopotamia, Egypt, India, Greece and Rome, likely owing to their absorbency and tissue adherent properties" said Gaharwar. "Ancient peoples would make a paste out of water and clay particles and apply it to wounds to stop bleeding faster."
Fascinated by the particle's blood clotting properties, Gaharwar began to explore the potential uses of a synthetic particle, which would avoid the potential risk of infection that comes with natural clays.
The challenge is getting this particle to the injury site and keeping it there. High blood flow washes powders and pastes away. Not only does this fail to stop the bleeding, it risks killing the patient in another way. The nanosilicate particles are small enough to easily travel through blood vessels to non-injured areas of the body, causing life-threatening blood clots and embolism.
With the help of Maitland's lab, the researchers combined the nanosilicate particles with an expanding foam. While completely stable in its applicator device, the particle-laced foam reacts to body heat. Once injected into a wound site, it expands to fill up the entire space, sealing severed blood vessels and holding the blood-clotting nanosilicate exactly where it needs to be. Since the foam forms a single piece, there is no risk of particles breaking away and traveling to form dangerous blood clots in other areas of the body.
In Ware's lab, the researchers took an entirely different approach: micro-ribbons. This biomaterial is delivered in the form of multiple ribbon-like structures, each covered in coagulation-promoting nanosilicate particles.
Like the foam, the micro-ribbons exploit the patient's body heat to trigger a reaction once in place. Each ribbon is made of two different materials, only one of which reacts to body temperature. Once in contact with the patient's body, one side of the ribbon contracts, causing it to curl. As multiple ribbons curl at the injury site, they tangle together to form a single foam-like structure. Even if a single ribbon were able to escape, its size prevents it from traveling through blood vessels, keeping the blood-clotting nanosilicate exactly where it needs to be.
The combined expertise of all three research labs may be responsible for the future of trauma care.
"If these materials get into the first aid kits in an ambulance as well as a soldier's backpack, they can save a lot of lives," said Gaharwar. "If you can save 30-40% of hemorrhagic shock victims, that is a big achievement."
By James Cavin, Texas A&M University College of Engineering
