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- In the state of effect: tumors are offered to be treated with light without chemical agents
In the state of effect: tumors are offered to be treated with light without chemical agents
Russian scientists have made a discovery that could change approaches to the diagnosis and treatment of cancer. It allows us to review the traditional methods of photothermal and photodynamic therapy. Now they use light-absorbing agents. These substances are delivered to tumor tissues to convert light into heat or chemical energy to destroy cancer cells. The "agent-free" strategy reduces the toxic load on the body from such substances: the tumor can be treated purposefully without affecting healthy tissues. However, the research is still fundamental, and it will take a long time before the methodology is put into practice, experts interviewed by Izvestia noted.
Electronic light and agent-free treatment
Researchers at Kazan Federal University (KFU) have explained how electronic light causes photorheating of transparent nanomaterials. This mechanism opens up new possibilities for the diagnosis and therapy of oncological diseases.
A study published in the journal Laser & Photonics Reviews shows how optically transparent heterogeneous systems, that is, formed from components with different properties, can capture light through scattering rather than absorption. The team of scientists found out that the interaction of light with spatially limited media changes the momentum of electrons in a similar way as photons transfer momentum to electrons in bulk crystals.
— The intrigue of our research is that an optically transparent medium begins to heat up as soon as it becomes heterogeneous. This reveals a previously unknown mechanism of optical heating of media that do not absorb light," said Sergey Kharintsev, Head of the Department of Optics and Nanophotonics at the Institute of Physics. — Our discovery forces us to reconsider the established methods of photothermal and photodynamic (PDT) therapy.
According to him, they traditionally use light-absorbing agents: photosensitizers, organic dyes and metal nanowells, which are targeted to tumor tissues to convert light into heat or chemical energy that destroys cancer cells. The new approach makes it possible to directly use light in living systems for therapeutic purposes without introducing external agents, he added.
The "agent-free" strategy turns photothermal therapy into a powerful and non-invasive tool: it is possible to treat a tumor in a targeted manner, leaving healthy tissues intact. As the scientists told Izvestia, the first attempts to use light to treat tumor diseases relied on the resonant absorption of super-powerful laser radiation, which damaged both diseased and healthy tissues, so the method was not widely used. In addition, standard photothermal therapy approaches do not allow cancer cells to be diagnosed.
"To demonstrate the physical principle, we deliberately chose a simple chemical system, a dean/water microemulsion stabilized with a surfactant," said Elina Battalova, the first author of the article, an engineer at the Department of Optics and Nanophotonics.
Conceptually, such an environment is capable of simulating a malignant tumor that can be selectively destroyed by nonresonant excitation using inelastic light scattering rather than absorption.
"By selecting the excitation wavelength and pumping power, it is possible to target the tumor by directing non—resonant light directly at the malignant tissue," explained Elina Battalova.
Although the main results of the study were obtained on a model chemical system, in the future they can be applied to living organisms, which expands the horizons of application of thermo-optical technologies. The strategy based on photorheating transparent heterogeneous media through scattering rather than light absorption opens the way to non—invasive, high-precision ablation of structurally complex tumors while fully preserving the surrounding healthy tissues, the scientists said.
Prospects for the emergence of a new method of oncotherapy
The rejection of photosensitizers removes the main harm of classical PDT — chemical toxicity and the recovery period in the dark for the patient, molecular biologist Arina Kholkina told Izvestia. In theory, the new technology is much safer for the patient.
— However, so far the data has been obtained only on microemulsions, and not on living tissues. A tumor is not just a "heterogeneous environment", it contains collagen, blood vessels, and inflammation. It is unknown whether the light will start warming healthy areas with a similar structure (for example, scars or foci of fibrosis) as strongly. The direction is very promising and currently requires a biological check," she said.
There is a long way between an unusual physical effect in microemulsion and real clinical technology: it needs to be proved that this mechanism is reproduced in living tumor tissue at all, that it really selectively damages tumor cells. In addition, malignant neoplasms are extremely heterogeneous and can form resistance to treatment, said Maxim Kotov, a market expert at NTI Helsnet, an oncologist at the N.N. Petrov National Research Medical Center of Oncology.
— Classical photodynamic therapy, by definition, requires a photosensitizer and the formation of reactive oxygen species, therefore it is more correct to speak not about "photodynamic therapy without agents", but about a potentially new mechanism of light heating of inhomogeneous media, — said the specialist.
The researchers have described a new physical mechanism that may have oncological applications in the future, but it is very early to talk about a ready-made breakthrough in cancer treatment, Maxim Kotov noted.
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