Healing power: Infected wounds will be treated with light and polymers.

Scientists from Russia and China have shown how the effectiveness of photodynamic therapy of infected wounds can be improved. In an experiment on mice, the combination of a photosensitive substance and polymer components accelerated healing, reduced inflammation, and contributed to a more complete restoration of the skin. The method looks promising, but the results of animal experiments cannot be directly transferred to humans: clinical studies are needed to assess the safety of the approach, experts told "Izvestia". For more information on whether such therapy can become an alternative to antibiotics, the resistance of bacteria to which is growing, see the "Izvestia" article.

Healing wounds with light

Scientists at Sechenov University, together with colleagues from the N.N. Semenov Institute of Chemical Physics of the Russian Academy of Sciences and Shanghai Ninth People's Hospital at Jiaotong University, have found a way to improve the treatment of infected wounds with light. This therapy works as follows: a special photosensitive substance is applied to the damaged area, and then light of a certain wavelength is applied to it. Under the influence of radiation, the formation of reactive oxygen species is triggered, which damage bacteria. At the same time, they act on different cellular structures at once, so it is more difficult for microorganisms to develop resistance to such effects than to antibiotics.

The researchers compared several options for such therapy. Methylene blue and an e6 chloride derivative were used as photosensitive substances, and Pluronic F108 polymer and sodium alginate were added to increase their effectiveness. The first helps photosensitive molecules to remain active, and the second creates an environment favorable for tissue repair.

The results of the approach were tested on mice with skin wounds infected with Staphylococcus aureus. The animals underwent two sessions of photodynamic therapy and were monitored for healing for 13 days. The wounds closed most quickly when using combined formulations with polymers: in the most effective groups, they were practically closed by the ninth day. Systems based on methylene blue showed particularly good results.

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When examining the recovered tissues, the scientists found not only a reduction in inflammation, but also the formation of mature connective tissue, ordered collagen fibers and new hair follicles. This indicates the restoration of the normal structure of the skin, and not only the rapid closure of the damage.

— It was important for us to evaluate not only the healing rate, but also the quality of the new tissue. We have seen that the right combination of ingredients helps to suppress inflammation faster and move on to skin repair. When using the most effective formulations, mature tissue with normal collagen organization was formed, and even hair follicles were restored. This indicates the potential of this approach specifically for full—fledged regeneration, and not just wound closure," said Yana Hristidis, head of the Laboratory of Regenerative Veterinary Medicine at the Institute of Regenerative Medicine at Sechenov University.

The prospect of a new method

The work combined the expertise of Russian scientists in the field of photochemistry and regenerative medicine and the research of Chinese colleagues on an experimental model of infected wounds. The results obtained can become the basis for further development of photodynamic systems for the treatment of such complex-healing injuries.

Photodynamic therapy has been formally studied in medicine, biology, and microbiology since 1900. ""The clinical application of the method has a half-century history," Mikhail Poltoratsky, an assistant at the Department of Faculty Surgery No. 1 at the Institute of Surgery at Pirogov University, a surgeon at the Moscow Medical Center "Kommunarka", told Izvestia.

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— The method is already used in oncology and dermatology. This article presents the results of the photodynamic approach in the treatment of wounds. Photosensitizers were studied: a solution of methylene blue in combination with polymers F108 (pluronic) and SA (sodium alginate). Positive results were obtained. When exposed to light, the tissues moved faster from the inflammatory phase to the regeneration phase. My opinion is that the method can be effective and can take its place in clinical practice," he said.

Interest in this method is growing as bacteria become more resistant to antibiotics, said Maxim Sychev, a family doctor and expert at the National Technology Initiative.

— The main difficulty of the method is related to the fact that the photosensitive substance remains in the wound for a long time and acts exactly where it is needed. The selection of polymer components is aimed precisely at this task. The results obtained in mice should be transferred to humans with great care. The skin of rodents heals differently: in humans, recovery is slower and more difficult," he said.

In addition, the most difficult cases in the clinic are associated with chronic infected wounds in patients with diabetes or circulatory disorders, where bacteria form protective films. Only clinical trials will show how effective and safe the method is in such conditions, the expert emphasized.

The results are published in the journal Frontiers in Chemistry.​