RHTU of Mendeleyev: Aero gels for a stop of severe bleedings

Main article: Polymers in medicine

2020: The announcement of aero gel on the basis of chitosan biopolymer for a fast stop of massive bleedings

On September 24, 2020 it became known that scientists from RHTU of D.I. Mendeleyev developed aero gels on the basis of biopolymer chitosan for a fast stop of massive bleedings. These are porous particles which can be entered into wounds locally: they inflate, absorbing erythrocytes and other components of blood, and the dense blood clot is as a result formed. Together with colleagues from SPKHFU Ministry of Health Russia scientists tested on laboratory animal (pigs) who showed that particles of aero gels stop bleeding in 2-3 minutes, and have no characteristic shortcomings or side effects of the direct analogs presented at the market. Article about a research is published in September in the Polymers magazine.

(A) Drawing a wound to a laboratory animal (B) Appearance of a wound after introduction of aero gel of chitosan (B) appearance of a wound after removal of aero gel. During creation of the image illustrations from the Polymers (MDPI) magazine are used.

As it was explained, according to the statistics abundant blood losses serve as the first reason of death at injuries, at the same time it is possible to stop a wound by different methods. Often for a bleeding stop enough dressing means like a gauze or bandage. But chances of the massive pulsing bleedings during which the person can lose critical amount of blood in read minutes, and normal methods not to cope with them. For September, 2020 they are stopped generally using porous materials on the basis of zeolites, but they have serious side effect - at hit of zeolites in wounds reactions with heat production begin, and as a result on a body there are burns. Therefore scientists look for other styptic materials which will be at the same time effective and safe.

Development of the Russian scientists is based on chitosan - biopolymer which is received from armors of Crustacea. It has a suitable biocompatibility and therefore chitosan is used in coverings of prostheses (including artificial valves of heart), the systems of address delivery of drugs, frameworks for recovery of a bone tissue and other biomedical purposes. And in this work scientists made aero gel on the basis of chitosan - so call solid, porous materials which for 99% consist of air. They have such total area of a time that if their everything could be rolled on one plane, then there would be enough 10 grams of aero gel for one football field.

We combined properties of chitosan with properties of aero gels and so received effective styptic material which works not simply better, than chitosan in itself, but also it is better, than many modern analogs - it is safer and more convenient at comparable cost value and styptic properties. Together with colleagues from the St. Petersburg state chemical pharmaceutical university we tested on pigs: put them damage of a trunk vessel then 45 seconds went active bleeding, and then using the applicator entered aero gel particles into a wound. In 2-3 minutes the steady blood clot skintight to edges of a wound formed and bleeding completely stopped. Darya Lovskaya, the original author of work, the research associate of the International educational scientific center of a transfer pharmaceutical and biotechnologies of RHTU told

After particles of aero gel of chitosan get to a wound they begin to bulk up promptly: absorb the different biological liquids and gases which are selected from a wound and also at the expense of a positive charge of molecules of chitosan erythrocytes which surface is loaded negatively are attracted. As a result aero gel inflates and completely closes a wound, stopping bleeding.

Aero gel was received in several stages: at first synthesized chitosan hydrogel, i.e. mesh structure with abundance of the time filled with water. After that hydrogel was processed alcohol so that to replace all water. And at last, after that, the received gel was dried in the environment of a critical fluid - a carbon dioxide gas which is in the special device with a pressure of 73 atmospheres and temperature of 31 degree. In such conditions the fluid gradually forced out all alcohol, releasing a time, but at the same time without destroying structure of material, and as a result hydrogel at last turned into aero gel.

Scientists used chitosan with a different molecular weight and analyzed structure of the received materials. The best characteristics showed aero gels on the basis of the shortest molecules of chitosan: their porosity was 97%, and density - only 28.6 kg/m3, i.e. almost all volume of material fell on the time filled with air (for comparison: the brick of the standard size made of such aero gel would weigh no more than 60 grams). At the same time the most part of a time had a diameter more than 0.5 microns that is ideal for adsorption of erythrocytes.

Appearance of aero gel of chitosan

After scientists tested the best samples on laboratory animals - six adult pigs. Put to pigs the injury of a femoral artery imitating a bullet wound and after 45 seconds of the free expiration of blood, injected drugs and then determined their action by the standard procedure of testing of styptic means. To estimate efficiency of materials scientists compared action of particles of aero gels on the basis of chitosan to pure chitosan in the form of powder.

Aero gels of chitosan and pure chitosan showed similar results: bleedings stopped in 2-3 minutes after introduction of medicine and did not renew within three hours of observations, the average volume of the lost blood was 425 ml, and at the end of tests all animals underwent mid-flight test: to them bent and unbent the injured leg, imitating walking, but bleeding did not renew.

At the same time aero gels had several advantages before particles of pure chitosan. First, pure chitosan in the form of powder can be distributed unevenly on a wound surface, i.e. it will be partially open for an infection while it is possible to enter particles of aero gel locally and precisely using the applicator, and after their fast swelling they will close all wound without gaps. Secondly, chitosan powder often sticks to edges of a wound and then it is very difficult to separate them from fabrics that complicates surgical work after a bleeding stop while with aero gels of such problems does not arise, and it is easy to delete them from a wound.

Haemo static medicines on the basis of powders of pure chitosan are already provided in scientific works and are even brought to the market, but except other shortcomings they have one more serious side effect - are net chitosan can disperse on an organism together with a blood-groove and to cause thrombosis. Chitosan aero gels have no such ghost effects as they have the form of spherical particles from 1 to 3 cm in size: such particles owing to the sizes cannot go to a blood-groove, and separate molecules of chitosan from the sewed structure of aero gel do not separate. However as haemo static materials chitosan aero gels before they were not considered - there are only separate scientific works where the structure of similar materials is optimized for sorption of oil spills. Nevertheless all experiments showed prospects of aero gels of chitosan as styptic means and therefore researchers are going to develop the production technology of the created material further.

In military medicine there is such term as gold hour - if within the first hour not to render the due help, then it can become a cause of death. And with massive venous or arterial bleedings the account in general goes for minutes and if any means wins even one minute in comparison with analogs this already great achievement. We showed that our means stops bleedings at scales of 2-3 minutes without characteristic ghost effects of analogs - it does not cause burns as zeolites and is not capable to cause thromboses as pure chitosan. Darya Lovskaya, the original author of work, the research associate of the International educational scientific center of a transfer pharmaceutical and biotechnologies of RHTU added

Scientists already took out the patent for the material, further they will upgrade its structure so that to reduce even more bleeding time, having saved all other advantages and features of material.