Massachusetts
Institute of Technology (MIT) engineers have developed a nanoscale biological
coating that can halt bleeding nearly instantaneously, an advance that could
dramatically improve survival rates for soldiers injured in battle.
The
researchers, led by Paula Hammond and funded by MIT’s Institute of Soldier
Nanotechnologies and a Denmark-based company,
Ferrosan Medical Devices A/S, created a spray coating that includes thrombin, a
clotting agent found in blood. Sponges coated with this material can be stored
stably and easily carried by soldiers or medical personnel. The sponges could
also prove valuable in civilian hospitals, says Hammond, the David H. Koch
Professor in Engineering.
“The
ability to easily package the blood-clotting agent in this sponge system is
very appealing because you can pack them, store them, and then pull them out
rapidly,” she says.
Hammond
and her colleagues described the technology in an online edition of Advanced
Materials. Lead author of the paper is Anita Shukla PhD ’11, who is now a
postdoc at Rice University.
Uncontrolled
bleeding is the leading cause of trauma death on the battlefield. Traditional
methods to halt bleeding, such as tourniquets, are not suitable for the neck
and many other parts of the body. In recent years, researchers have tried
alternative approaches, all of which have some disadvantages. Fibrin dressings
and glues have a short shelf life and can cause an adverse immune response, and
zeolite powders are difficult to apply under windy conditions and can cause
severe burns. Another option is bandages made of chitosan, a derivative of the
primary structural material of shellfish exoskeletons. Those bandages have had
some success but can be difficult to mold to fit complex wounds.
Many
civilian hospitals use a highly absorbent gelatin sponge produced by Ferrosan
to stop bleeding. However, those sponges need to be soaked in liquid thrombin
just before application to the wound, making them impractical for battlefield
use. Hammond’s
team came up with the idea to coat the sponges with a blood-clotting agent in
advance, so they would be ready when needed, for either military or civilian
use.
To
do that, the researchers developed a nanoscale biological coating that consists
of two alternating layers sprayed onto a material, such as the sponges used in
this study. The researchers discovered that layers of thrombin, a natural
clotting protein, and tannic acid, a small molecule found naturally in tea,
yield a film containing large amounts of functional thrombin. Both materials
are already approved by the U.S. Food and Drug Administration, which could help
with the approval process for a commercialized version of the sponges, Shukla
says.
A
key advantage of the spray method is that it allows a large amount of thrombin
to be packed into the sponges, coating even the interior fibers, says David
King, a trauma surgeon and instructor in surgery at Massachusetts General
Hospital who was not involved in this research.
“All
of the existing hemostatic materials suffer from the same limitation, which is
being able to deliver a dense enough package of hemostatic material to the
bleeding site. That’s why this new material is exciting,” says King, also an
Army reservist who has served in Afghanistan as chief of trauma
surgery.
Once
sprayed, the sponges can be stored for months before use. The sponges can also
be molded to fit the shape of any wound. “Now we have an alternative that could
be used without applying a large amount of pressure and can conform to a
variety of wounds, because the sponges are so malleable,” Shukla says.
In
tests with animals at Ferrosan, the coated sponges were applied to wounds, with
light pressure (from a human thumb), for 60 sec—and stopped the bleeding within
that time. Sponges lacking thrombin required at least 150 sec to stop the
bleeding. A simple gauze patch, applied for 12 min (the length of the experiment),
did not stop the bleeding.
The
researchers have filed a patent application on this technology and on similar
sponges coated with the antibiotic vancomycin. Hammond’s laboratory is now working on
combining the blood-clotting and antibiotic activities in a single sponge.
