When injected into the bloodstream of rats with a nick in the femoral artery–the large artery in the thigh muscles–the nanoparticles bound activated platelets at the injury site. The treatment halved bleeding time in the rats from about four minutes to two, proving more effective than NovoSeven. The research was published this week in the journal Science Translational Medicine.
Lavik says the two treatments might prove to be complementary. NovoSeven, she says, “works to help build the fibrin mesh network that’s critical in building clot. Perhaps the synthetic platelets could help start building the clot and the drug might help stabilize it.”
“It sounds like it has the potential to be useful for controlling bleeding on the battlefield,” says John Weisel, a biologist at Penn Medical School, who was not involved in the research.
Early studies suggest the nanoparticles are safe, a major issue for treatments that enhance blood clotting. By studying fluorescently labeled versions of the nanoparticles, researchers found that the particles are easily cleared from the body. And the particles do not accumulate in noninjured tissue, such as the lungs or kidneys, to form dangerous clots. At very high doses–a concentration almost too thick to move through the syringe, says Lavik–the particles did trigger breathing issues in some animals. But such a high dose isn’t necessary to generate blood-clotting benefits, she says.
Nevertheless, extensive testing is needed before the particles can be used in humans. “The early research looks very promising, but the human system is different than a rat’s,” says Rutledge Ellis-Behnke, a researcher at MIT. “Care has to be taken that these do not coat the inside of the lungs and reduce the amount of oxygen transfer into red blood cells.”
Researchers plan to test the particles in larger animals, which more closely approximate the human circulatory system, as well as in different types of injuries, such as those that mimic the blast injuries that are particularly common among troops in Iraq and Afghanistan.