ИСТИНА

AIM Laser trapping and manipulation of blood cells without mechanical contact have become feasible with implication of laser tweezers. They open up new horizons for the hemorheologic research as they offer new possibilities for studying live cells interactions on individual cell level under the influence of different endogenous and exogenous factors. Here we discuss the basic features of these techniques and some examples of challenging hemorheologic studies. METHODS The operation principle of laser tweezers is based on the property of strongly focused laser beam to act on the dielectric microparticles located in the vicinity of the beam waist with a force that drives the particle to the equilibrium location and holds it there. If the beam waist position is manipulated, so is the position of the particle. The displacement of the particle from the equilibrium position by external forces can be calibrated so that these forces can be precisely measured in the range ca. 0.1 – 100 pN. RESULTS This is the range of forces of elastic deformation of blood cells, e.g., by shear stresses, and of their interaction with each other, e.g., during aggregation, and with vessel walls. CONCLUSIONS We conclude that being able to measure these forces without mechanical contact allows for studying on single cell level the mechanisms of interactions that was impossible earlier.