ИСТИНА

With the advent of laser tweezers, for the invention of which Arthur Ashkin (USA) was awarded the 2018 Nobel Prize, optical trapping and manipulation of live cells without mechanical contact became practically feasible. The use of laser tweezers has opened new horizons for scientific and technological advances and developments, since it has provided new opportunities for studying the many phenomena in the molecular-cell interface that form the basis of living matter. However, the absence of mechanical contact does not always ensure the integrity of the living cell trapped by the laser beam, even though the laser wavelength is selected so as to be outside the absorption spectrum of the cell. This circumstance requires additional research. The principle of operation of laser tweezers is based on the property of a sharply focused laser beam to exert an effect on dielectric microparticles located near the waist of this beam with a force that brings the particles to an equilibrium position and holds them there. A change in the spatial position of the beam waist leads to a change in the position of the trapped particle. The removal of a particle captured by the laser tweezers from the equilibrium position by external forces can be calibrated so that these forces can be accurately measured in the range of 0.1-100 pN. This is the range of forces of elastic deformation of living cells and their interaction with each other. The ability to measure these forces without mechanical contact makes it possible to study the mechanisms of their interaction at the level of individual cells, which was previously impossible. In this paper, we show the possibilities of studying with the help of laser tweezers various phenomena underlying the interaction of individual red blood cells (RBC) suspended in autologous plasma or in solutions of different macromolecules, somehow affecting the properties of these cells [1-3]. We demonstrate the phenomenon of synergy discovered by us in the action of various components of blood plasma, which plays a significant role in the aggregation of RBC and significantly affects blood mirocirculation. Also, we demonstrate that the microrheologic properties of RBC depend on their age, i.e. the duration of their presence in the microcirculation after they leave the blood marrow. This is caused, in particular, by the difference in adsorption of macromolecules by the membranes of RBC of different age and, also, by pathologic alterations [4-6]. We present our preliminary results in measuring the forces of interaction of RBC with endothelial cells in vitro ranging from 0 to 21 pN depending on the shape of RBC (discocytes or ehinocytes), concentration of macromolecules (fibrinogen or dextran) in the suspending medium, and preactivation of the endothelial cells with the tumor necrosis factor TNF-α [7]. The work was supported by the Russian Foundation for Basic Research (grant No. 19-52-51015). [1] A.V. Priezzhev and K. Lee, Potentialities of laser trapping and manipulation of blood cells in hemorheologic research, Clin. Hemorheol. Microcirc. 64, 587–592 (2016). [2] K. Lee, A.V. Danilina, M. Kinnunen, A.V. Priezzhev, and I. Meglinski, Probing the red blood cells aggregating force with optical tweezers, IEEE J. Sel. Topics in Quant. Electron. 22(3), 7000106 (2016).
 [3] K. Lee, C. Wagner, and A.V. Priezzhev, Assessment of the “cross-bridge”-induced interaction of red blood cells by optical trapping combined with microfluidics, J. Biomed. Opt. 22(9), 091516 (2017). [4] P.B. Ermolinskiy, A.E. Lugovtsov, A.I. Maslyanitsina, A.N. Semenov, L.I. Dyachuk, and A.V. Priezzhev, Interaction of erythrocytes in the process of pair aggregation in blood samples from patients with arterial hypertension and healthy donors: measurements with laser tweezers, JBPE 4(3), 030303 (2018). [5] K. Lee, E. Shirshin, N. Rovnyagina, F. Yaya, Z. Boujja, A. Priezzhev, and C. Wagner, Dextran adsorption onto red blood cells revisited: single cell quantification by laser tweezers combined with microfluidics, Biomed. Opt. Express 9(6), 2755-2764 (2018). [6] A.N. Semenov, E.A. Shirshin, A.V. Muravyov and A.V. Priezzhev, The effects of different signaling pathways in adenylyl cyclase stimulation on red blood cells deformability, Frontiers in Physiology 10, №923б 1-10 (2019). [7] A.A. Kapkov, A.N. Semenov, P.B. Ermolinskiy, A.E. Lugovtsov, and A.V. Priezzhev, Forces of RBC interaction with single endothelial cells in stationary conditions: measurements with laser tweezers. Submitted to JIOHS.