ИСТИНА

The composition of the blood, as well as the parameters characterizing the structure and dynamics of blood and tissues surrounding blood microvessels, are the factors that determine the fluidity of the blood and the efficiency of the transport and delivery of gases (oxygen and carbon dioxide) and nutrients throughout the volume of the human body. Age-related changes in the body and most socially significant diseases are accompanied and largely determined by the deviation of these parameters from normal values. Thus, the ability to measure and control these parameters in normal conditions and their changes in pathology is important for an adequate assessment of the state of patients, ways to improve the treatment procedure and to correct the microrheology and microcirculation of the blood of patients. In modern hemorheological studies, laser and optical methods are widely used, which allow performing a comprehensive study of deviations from the norm of various parameters associated with the structure and dynamics of blood, through visualization and measurement. In particular, the following ones are used: diffuse light scattering (DLS); laser diffractometry (LD); optical tweezers (OP), videocapillaroscopy, speckle-contrast spectroscopy, two-photon tomography, and fluorescence imaging. The first three methods are used for in vitro measurements using fresh EDTA-stabilized blood samples drawn from healthy donors or patients suffering from various diseases, such as diabetes mellitus and arterial hypertension. The last four methods are used for in vivo measurements and imaging. Also, parameters associated with erythrocyte aggregation are measured in model solutions of certain plasma proteins known as aggregation agonists or inhibitors to study the mechanisms of aggregation. In particular, the forces of aggregation and disaggregation of individual erythrocytes are measured using the OP, the aggregation index, the characteristic aggregation time and the critical shear stress in whole blood samples are mesured with an aggregometer using the DLS method. In our work, the conventional LD (ektacytometry) method used to measure the average value of the deformability of erythrocytes in a sample is improved in such a way that it becomes possible to measure the parameters of cell distribution in deformability, which is important for the clinical application of the method. The blood flow in capillaries is imaged using the digital capillaroscopy techniques, which allows for determining several parameters of the flow in nail-bed capillaries of human individuals. Also, in vivo imaging of blood flow in larger areas of the microcirculatory system in laboratory animals is performed using the laser speckle-contrast spectroscopy method. The work was supported by the Russian Science Foundation (grant No. 23-45-00027) and performed according to the Development program of the Interdisciplinary Scientific and Educational School of Lomonosov Moscow State University «Photonic and Quantum technologies. Digital medicine».