Light that kills bacteria
An alternative to antibiotics is being created in Russia
According to the World Health Organization, one of the most serious threats to humanity is the resistance of bacteria to antibiotics, which is rapidly growing due to their uncontrolled use. In the project of Russian scientists, the physical part of which is implemented by specialists of the National Research Nuclear University "MEPhI" (NRU MEPhI), a possible solution to this problem is proposed. The new development, according to the authors, will facilitate the treatment of difficult-to-heal wounds, burns and other foci of bacterial threat. About the latest achievements of Russian scientists – in the new material of RIA Novosti.
Zero resistance
One of the solutions to this global problem, according to scientists, may be the development of methods of antibacterial photodynamic therapy (PDT). According to the results of many studies, pathogenic microorganisms are unable to develop resistance to this type of treatment.
The principle of operation of PDT is based on the use of special substances, photosensitizers, injected into the body and irradiated with light during treatment using a special emitter. The resulting light energy is transferred to oxygen molecules and transforms them into an active form that fights infection.
A team of scientists, including physicists from IOF RAS and NRU MEPhI, microbiologists from N.F. Gamalei NITSEM and chemists from the Research Center "NIOPIC", proposed using synthetic polycationic bacteriochlorins as photosensitizers. Unlike most antibiotics that target only one type of bacteria, these compounds have a universal effect when treated with PDT. According to scientists, in clinical practice, this will allow us to abandon the definition of the type of bacterial threat, thereby saving time and resources.
According to the WHO definition, an effective antibacterial agent is a drug that reduces the number of active pathogen cells by at least 1000 times. According to the scientists of the MEPhI Research Institute, the bacteriochlorins they use exceed this indicator by at least 10 times.
What are bacteria afraid of?
This efficiency is achieved, firstly, due to the ability of bacteriochlorins to strong light absorption and subsequent energy transfer to oxygen present in the body. The rapid death of bacteria is ensured by the action of the active form of oxygen, "charged" with energy from the photosensitizer.
Secondly, bacteriochlorins in solution have a positive electric charge, which, according to recent studies, increases the effectiveness of photosensitizers on bacteria both in the free state and in the form of biofilms.
Thirdly, bacteriochlorins perfectly absorb light in the near infrared range. As the scientists explained, in this region of the spectrum there is a so-called "window of transparency of biological tissue", that is, light with such a wavelength is able to penetrate much deeper into the tissues of the body. In addition, the light absorption of pigments released by some types of pathogenic bacteria is reduced in this range, so that much more energy will be supplied to activate the photosensitizer.
"Experiments have shown high efficiency of bacteriochlorins on strains of bacteria that are resistant to antibiotics, and these were both less aggressive gram-positive bacteria and more aggressive gram-negative ones. This seriously increases our chances of success in real clinical work," said Ekaterina Akhlyustina, a graduate student of the Engineering Physics Institute of Biomedicine at MEPhI.
Let there be light
The most promising field of application of antibacterial PDT is the treatment of severe and long–lasting infected wounds and burns, according to the scientists of the MEPhI Research Institute. According to them, such a technique can not only accelerate recovery, but also provide a good cosmetic effect.
"At the current stage of testing, these compounds can already be used for technical purposes – for example, for high-quality disinfection of surfaces in hospitals. We hope that later a dosage form for use in medicine and veterinary medicine will be developed on the basis of bacteriochlorins," Ekaterina Akhlyustina said.
According to scientists, one of the physical problems in the development of the PDT method is the aggregation of the photosensitizer, that is, the formation of "lumps" of the substance that significantly reduce the effectiveness of therapy. Specialists of the NRU MEPhI are conducting active research to combat this phenomenon.
When developing new photosensitizers, as explained by the specialists of the MEPhI Research Institute, it is also necessary to carefully study the stability and photodynamic properties of the synthesized compounds. Subsequently, this will allow you to choose the right doses of drugs to create a dosage form of new compounds. The main thing in effective PDT, as explained by scientists, is to choose the necessary concentrations of substances and the right dose of light irradiation.
A patent has already been obtained for chemical compounds used by the research team as photosensitizers. The immediate task facing the researchers of the MEPhI Research Institute is spectroscopic studies of stable compounds of bacteriochlorins with minimal aggregation, as well as preparation for experiments on organs and tissues of experimental animals and humans.
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