ИСТИНА

Laser tweezers (LT) are scientific tools allowing to trap and manipulate of living cells without direct mechanical contact with them using highly focused laser beam [1]. Red blood cells (RBC) and interaction forces between them as well as the effect of optical trapping on the RBC elastic properties were extensively studied by LT [2]. However, there is no full understanding of the shape changes of RBC in the field of the laser beam as well as the influence of laser exposure on RBC membrane. The aim of this work was to study the effect of the highly focused laser beam with the wavelength of 1064 nm (at the power from 10 to 160 mW) on the trapped RBC using LT. The single RBC in the optical trap changes its orientation and acquires an asymmetric shape depending on the laser beam power at the focal point. In our study, RBC does not undergo significant changes during 5 min at the laser beam power less than 60 mW. At the power higher than 80 mW the RBC starts to fold and at that higher than 130 mW the RBC’s membrane breaks after 4-5 min of trapping. Additionally, it was found that the amplitude of the change in linear dimensions decreases with repeated short-term trapping of the cell by the laser beam of fixed power. It indicates a change in the rigidity of the RBC membrane. The obtained results are important both for understanding the mechanisms of the laser beam interaction with trapped RBC and for optimizing the technique when conducting optical experiments with them, especially for performing measurements of membrane mechanical properties using LT. This work was supported by the Russian Scientific Foundation (Grant No. 20-45-08004). [1] A.V. Priezzhev et al., “Optical Study of RBC Aggregation in Whole Blood Samples and Single Cells,” Chapter 1 in “Handbook on Optical Biomedical Diagnostics”, V. V. Tuchin – editor, 2nd Edition, SPIE Press Bellingham, WA, United States, 2016. [2] A. Ghosh et al. “Euler buckling-induced folding and rotation of red blood cells in an optical trap” Phys. Biol. 3, 67-73 (2006).