Synthetic platelets will stop the bleeding
Scientists at Case Western University (Cleveland, Ohio), working under the leadership of Erin Lavik, have developed synthetic nanoparticles that, when glued together with platelets contained in the blood, double the formation of a blood clot. When conducting experiments on rodents, their effectiveness turned out to be much higher than the effectiveness of the drug used to stop arterial bleeding.
The developers hope that in the future the new nanoparticles will primarily be useful to paramedics and military doctors. Preliminary testing of the safety of nanoparticles shows promising results, but the blood clotting system is very complex, and so far the creation of drugs that accelerate the formation of blood clots has been associated with quite great difficulties due to the risk of life-threatening side effects, such as a heart attack or stroke.
Uncontrolled blood loss is the main cause of post-traumatic death of people. The existing methods of stopping bleeding are mainly suitable only for the treatment of open wounds and use in the operating room. None of the currently used approaches can stop internal bleeding before arriving at a medical facility.
Traumatic damage to tissues and blood vessels triggers a cascade of blood clotting, starting with the activation of platelets. These small blood plates begin to stick together with each other and other blood cells, forming a clot. Doctors can accelerate the process of thrombosis with the help of drugs or materials containing protein components of the coagulation cascade. One of these drugs, NovoSeven, is a protein synthesized in accordance with the decoded sequence of a human gene. However, the cost of this drug is very high (from 10,000 to 30,000 US dollars) and some trauma surgeons express doubts about its effectiveness.
Attempts to create artificial platelets have so far failed. Previously proposed by scientists, particles and compounds that activate platelets have a certain effectiveness, but increase the risk of life-threatening blood clotting inside the capillaries.
The authors have developed nanoparticles that freely pass through the lumen of capillaries and selectively bind to the surface of activated platelets. Each nanoparticle has a polymer core covered with a layer of water-soluble polyethylene glycol (PEG) polymer molecules, preventing them from sticking to each other and the walls of blood vessels. Peptide sequences are attached to polyethylene glycol molecules, providing selective binding of nanoparticles with activated platelets.
When injected into rats with a damaged femoral artery, nanoparticles (in the picture they are colored green) bound to activated platelets in the damaged area (colored blue). As a result, the bleeding stopped within two minutes, whereas when using NovoSeven, it took four minutes. The results obtained by the authors are published in the December issue of the journal Science Translational Medicine in the article "Intravenous Hemostat: Nanotechnology to Halt Bleeding".
According to Lavik, NovoSeven accelerates the formation of fibrin fibers necessary for the formation of a clot. Perhaps its use to stabilize the clot formed with the help of nanoparticles will further reduce the time required to stop bleeding.
The results of preliminary tests indicate the safety of nanoparticles. Observation of the behavior of nanoparticles labeled with fluorescent dye showed that they are rapidly excreted from the body. They also do not accumulate in healthy tissues, which excludes the possibility of the formation of life-threatening blood clots. The introduction of extremely high doses of nanoparticles caused breathing problems in some animals, but Lavik claims that there is no need to introduce such doses to achieve the desired effect.
However, the human coagulation system is different from that of rats, so the researchers plan to test the nanoparticles on larger animals whose circulatory system is more similar to that of humans. They note that it is necessary to pay special attention to the fact that nanoparticles do not cover the inner surface of the vessels of the lungs, making it difficult for erythrocytes to saturate with oxygen.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of TechnologyReview: Synthetics Stop the Bleeding
21.12.2009