In silico studies of the interaction of wavelengths of direct optical excitation of molecular oxygen with biological tissues

Abstract

Oxygen and its partially reduced chemical products, known as reactive oxygen species (ROS), have important regulatory and signaling functions. ROS, along with active forms of nitrogen, play a special role in the regulation of vascular tone. The accumulated experience in studying the physiological and pathological role of ROS and identifying the mechanisms of their generation allowed to develop an interest in the singlet form of oxygen. It seems promising to use it in the field of fundamental and practical medicine to change the mechanisms of vascular tone regulation, start the processes of vasoconstriction and vasodilation, as well as the angiogenesis regulation.
To date, in addition to the classical mechanism of singlet oxygen excitation using photosensitizers, it has become possible to directly excite an oxygen molecule with light at certain wavelengths. The basic triplet state of oxygen has several absorption bands in the infrared and visible regions, at which singlet oxygen can be produced. Since oxygen absorbs light weakly enough, low absorption can be compensated by changes in light intensity and exposure time. The choice of the optimal combination of these parameters is important from the position of high absorption of laser radiation in biological tissue and heat generation, which can induce a number of effects and directly affect the analyzed processes.
In order to select the optimal ratio of laser radiation parameters and exposure time for subsequent research and to identify the effect of optical dose-dependent generation of singlet oxygen on changes of vascular tone regulation, in silico studies of the interaction of optical radiation of various wavelengths of direct optical generation of singlet oxygen with biological tissues and modeling of thermal effects were carried out. The brain tissues containing functionally active blood vessels and the nail bed area of the fingers were considered as analyzed objects.
Using the numerical Monte Carlo method, maps of the fluence rate (radiation power distribution) over the brain volume and the nail bed area and the corresponding radiation attenuation over the depth were obtained. The temperature distribution was calculated using the COMSOL Multiphysics heat transfer module by combining the Beer-Lambert law with the Pennes bioheat transfer equation. The study took into account the radiation energy, exposure time and the absorption coefficient of brain tissue and the of the nail bed of the fingers, including blood filling parameters. The simulation allows us to predict the optimal parameters of experimental singlet oxygen generation systems excluding heating of tissues in the brain and in the nail bed area.
The work was supported by the Russian Science Foundation under project No. 21-75-00086.

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Irina N. Novikova
Orel State University
Russia

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