Moments of enlightenment
To make an accurate diagnosis, the patient's organ can be made transparent for a while
Vasily Yanchilin, "Search" No. 36-2016
Listing all the important scientific achievements, awards, titles and positions of Professor Valery Tuchin of Saratov National Research State University named after N.G. Chernyshevsky could make this introductory part comparable in size with the main material. Therefore, let's just say that both domestic and international assessments of his activities note an "unprecedented contribution" to the scientific and educational spheres. Valery Viktorovich is a recognized authority in the field of biological and medical physics, biophotonics, biomedical optics and in a number of other areas. The scientific school headed by him, as one of the leading ones, received state support this year for the implementation of the innovative project "Optics and biophotonics of biological tissues: methods of medical diagnostics and therapy". The well-known scientist told our correspondent about the features of the study and the planned results.
– Let me remind you that optics, which plays a key role in this study, is one of the oldest scientific disciplines, – says Valery Viktorovich. – Its capabilities and properties have long been successfully used by mankind for various needs, including to improve the quality of life and preserve health. It is enough to name the objects and devices that we often use ourselves or meet in polyclinics and hospitals. These are glasses and contact lenses, ophthalmic and dermatological lamps, fibroscopes, LEDs, lasers.
The rapid development of electronics and its actual integration with optics in the last century led to the emergence of a new scientific discipline of photonics, within which fundamental and applied problems of generation, propagation and interaction of optical signals with various media are being developed.
It should be noted that the use of optical technologies in the diagnosis and treatment of diseases cannot be successful without understanding the interaction of optical radiation with biological tissues and cells. Therefore, in the XXI century, a new scientific discipline was formed – biophotonics, which arose at the junction of innovative disciplines of the last century, namely photonics, biotechnology and nanotechnology. All this has determined the features of technology development, as well as the training of highly qualified personnel in a new scientific direction. The solution of such problems is fully reflected in the well-known monographs and textbooks of the scientific school of the Saratov National Research State University named after N.G. Chernyshevsky.
Our pioneering research has a serious impact on the development of biomedical technologies in the world and the training of a new generation of researchers and teachers in the field of biophotonics. This is also due to the active participation of our research team in the organization of international conferences over the past 20 years – in Russia, the USA, European countries, China. For the first time in the world, we have developed new educational standards for the preparation of bachelors in physics of living systems and masters in biophotonics, which are being successfully implemented at the university and are planned to be used in a number of universities in our country, as well as Finland, Germany, China.
– What methods of medical diagnostics do you use and for what purpose?
– Within the framework of international cooperation, we are developing and offering a number of new medical optical diagnostic technologies for use in clinics and hospitals. For example, based on optical coherence tomography, which is successfully used to diagnose eye diseases and a number of skin diseases, including psoriasis and melanoma. Optical methods have great prospects in the diagnosis of cardiovascular diseases and brain diseases, including atherosclerosis, strokes, brain tumors. Their attractiveness is that it becomes possible to conduct continuous studies of the brain for many hours and days without harming this important organ, which cannot be provided in any other way using, say, ultrasound, MRI or X-ray computed tomography.
Of course, there are serious scientific and technological problems that we are successfully solving step by step. In particular, we are hindered by strong light scattering, which distorts the image of the object of study or even hides it completely. For clarity, examples can be given with an airplane flying in the clouds, or a grain falling into milk. Our eye does not see them. In medical research, similar situations arise when it comes to small cancerous tumors or cancer cells moving through the vessels (metastases).
Our task is to provide reliable and high–quality visualization of such objects. To do this, we use different methods. For example, we make cells "sound" under the influence of pulsed laser radiation, which can penetrate deep into biological tissue. It is possible to make the fabric more transparent by impregnating it with substances that temporarily eliminate light scattering. Do you remember the Invisible Man by H.G. Wells? Of course, we cannot make the whole person transparent, but individual organs and tissues are completely transparent. Nature itself has shown us the way to this. The cornea of the eye, through which the light from the object in question falls on the sensitive shell of the eye – the retina, has excellent transparency. The sclera of the eye, covering the eyeball from the outside along with the cornea, is very close to it in its structure. Both tissues consist of collagen fibers, which serve as a kind of reinforcement that gives the eye mechanical strength. However, from the point of view of optics, they are completely different, the cornea is transparent, and the sclera is white, opaque (this is the white of the eye). This difference is due to the heterogeneity of the structure of the sclera. But for a while it can be made more homogeneous – with the help of drops of an illuminating agent, it becomes more transparent. The study of differences in the structure of the cornea and sclera provides valuable information for the development of universal technologies for the enlightenment of other tissues and organs, including skin, muscle tissue, and not only soft, but also hard tissues – cartilage, bone and dental.
Thanks to the advent of high-speed powerful computer tools, it has become possible to control the trajectories of photons in highly scattering media using so-called adaptive (self-adapting) mirrors and screens that correct blurred images of biological tissues, make them clearer and more informative.
– I would like to know about the methods of treatment you offer and their results.
– We are developing a number of phototherapy methods and their combinations. Light is used to trigger photochemical reactions using special dyes or nanoparticles. Dyes can also be produced by the body itself, which is especially interesting if the increased concentration of the dye is due to the development of a pathological process. For example, such widespread diseases among young people as acne or gum inflammation are accompanied by the proliferation of microbes that are pigmented and for this reason absorb light very effectively. By launching chains of photochemical reactions with the generation of free radicals (particles with increased reactivity), it is possible to achieve the complete death of pathogenic microbes in these places.
The technology also works well for specially created dyes, which in one way or another are introduced into the area of pathological formations and, due to the generation of free radicals by light, kill not only microorganisms, but also cancer cells. This is the so-called photodynamic therapy method, which is already used in clinics for the treatment of oncological and inflammatory diseases. Nevertheless, it requires further development to ensure greater effectiveness, especially for the treatment of deep-lying tumors.
Currently, various nanoparticles, which can be metallic, semiconductor or organic, are used as intermediaries for the effect of light on cells and tissues. Under the influence of light, they heat up or generate free radicals and therefore damage or kill pathological cells. Similar processes are used for cell nanosurgery and the introduction of genetic material into the cell. However, many problems need to be solved before such nanotechnologies enter medical practice. One of these problems is related to the delivery of nanoparticles to the objects of impact, it must be vector, that is, strictly directed.
– What have you already done in this topic? How significant are your results in the scientific world, at the international level?
– Our team has carried out a number of priority studies on the optics of biological tissues, the development of methods for measuring the optical parameters of biological tissues in normal and in various pathologies, as well as the development of technology for optical illumination of tissues and cells, which is necessary to significantly improve the effectiveness of optical and laser diagnostic, therapeutic and surgical technologies. The results obtained are summarized in numerous monographs, textbooks, reference books, analytical reviews and special issues of journals and are widely used in practice. Our books and original works are well cited, the total number of citations exceeds 13 thousand. But it's not just about quoting. The results we have achieved serve as the basis for conducting large-scale clinical trials in world scientific centers.
In 2016, my book on the optics of biological tissues received the Joseph Goodman International Prize as a monograph that made a significant contribution to research, teaching and industry development in the field of optics and photonics. I have published the world's first monograph on optical illumination of biological tissues and blood. Our team is a world leader in the field of polarization optics and spectroscopy of biological tissues, optical technologies for measuring blood flow velocity and perfusion of biological tissues, including the brain, in the development of methods of flow optical and photoacoustic cytometry, in the application of plasmon nanocomposites with photodynamic dyes for selective laser destruction of cancer cells and pathogens.
– What tasks is the current project designed to solve, how promising are they for practical use?
– Our new project, supported by a grant from the President of Russia, is dedicated to the further development and application of methods for the quantitative determination of the optical properties of biological tissues, the study of the diffusion rate of optical brightening agents, drugs and dyes in tissues. These studies include a full cycle – from experimental demonstration of effects, their theoretical description using modern mathematical and computational methods to the development of experimental equipment and technology transfer into clinical practice.
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02.09.2016