Andrei Lugovtsov , Alexey Semenov [1, 2], Petr Ermolinskiy , Anastasiya Maslyanitsina , Larisa Dyachuk , Elena Pavlikova , Yuri Gurfinkel , Alexander Priezzhev [1, 2]
 International Laser Center, M.V. Lomonosov Moscow State University, Leninskye Gory 1-62, 119991
Moscow, Russian Federation
 Department of Physics, M.V. Lomonosov Moscow State University, Leninskye Gory 1-2, 119991
Moscow, Russian Federation
 Medical Research and Education Center, M.V. Lomonosov Moscow State University, Lomonosovsky pr-t, 27-10, 119991, Moscow, Russian Federation
Complex studies of alterations of rheological and microrheological parameters of blood drawn from patients suffering from such a socially significant disease as arterial hypertension were conducted by optical methods. The rheological parameters are mostly related to the deformability and aggregation properties of red blood cells, which are expected to be impaired in patients with arterial hypertension. Thus, it is necessary to control the parameters of the blood flow during diagnostics and treatment.
The light scattering (laser aggregometry) and laser diffractometry techniques allows to assess parameters characterizing the ability of red blood cells to reversibly deform in shear flow and interact (aggregate) on ensembles of erythrocytes. All measurements with these techniques were performed by using the commercially available Rheoscan system (Rheomeditech, Korea). These techniques are convenient, fast and relatively simple for in vitro measuring the deformability and aggregation properties of erythrocytes. The essence of laser diffractometry is in obtaining and subsequent analysis of the obtained diffraction pattern from a highly diluted suspension of RBCs at rest and shear flow. Laser aggregometry technique allows to register the kinetics of the spontaneous aggregation (time dependence of light intensity forward scattered from a sample of whole blood at rest) and shear-induced disaggregation (shear stress dependence of light intensity backscattered from a sample of whole blood under shear flow) of RBCs for obtaining the characteristic time of aggregates formation (aggregation rate), aggregation index as well as hydrodynamic strength of aggregates .
Home-made double channeled optical tweezers (OT) was used for measuring the aggregation speed as well as interaction forces on cellular level . OT are formed by two single-mode Nd:YAG lasers and a water-immersion objective with high numerical aperture. OT allows for freely manipulating the individual cells with a tightly focused laser beam.
One more method that was used to evaluate blood rheology is capillaroscopy. This is simple non-invasive diagnostic technique designed to evaluate small microcirculation in the nailfold vessels.
All experimental measurements were performed with human blood drawn from patients with arterial hypertension (17 patients) and practically healthy volunteers (12 volunteers). Blood samples were stabilized with EDTA to prevent blood clotting. The measurements were performed within two hours after blood sampling.
It was shown that in patients with arterial hypertension the ability of erythrocytes to deform was slightly reduced while the aggregation speed and forces of erythrocyte interaction was significantly increased relatively to the control group. The blood microcirculation in nailfold capillaries was disturbed as well.
The work was supported by the RFBR grants №. 16-52-51050 and 17-02-01200.
 A.V. Priezzhev, N.N. Firsov, J. Lademann, Light backscattering diagnostics of RBC aggregation in whole blood samples, Chapter 11 in Handbook of Optical Biomedical Diagnostics, Editor V. Tuchin, Washington: SPIE Press, pp. 651 – 674 (2012).
 K. Lee, M. Kinnunen, M.D.Khokhlova, E.V.Lyubin, A.V.Priezzhev, I. Meglinski, A. Fedyanin, Optical tweezers study of red blood cell aggregation and disaggregation in plasma and protein solutions, Journal of Biomedical Optics, vol. 21(3), pp. 035001 (2016).
Dr. Andrei Egorovich Lugovtsov
International Laser Center of M.V. Lomonosov Moscow State University, Ph.D., reseacher
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