Affiliations: Laboratory of Biomedical Engineering, University of Patras, Patras 26500, Greece
Note: [] Corresponding author: G. Athanassiou, Biomedical Engineering Laboratory, Department of Mechanical Engineering and Aeronautics, University of Patras, Patras 26500, Greece. Tel.: +30 2610 969490; E-mail: gathan@mech.upatras.gr
Abstract: In the present study, the role of the nucleus and its contribution to the deformability of the passive neutrophils was investigated. To determine the rheological properties of the nucleus and of the neutrophil itself, deformation tests on single neutrophil and sequestered nucleus have been performed by micropipette under low aspiration pressure (80 Pa = 2–3 Pcr). The stiffness of the nucleus was found to be larger than that of the neutrophil, and its viscosity was found almost ten-fold higher. A subpopulation of neutrophils (Sub-A) showed two phases of deformation, a first rapid phase and a second phase with a constant deformation rate up to their full entrance, with an apparent viscosity μapp-second-Phase(NSub-A) = 286 ± 123 Pa·s, calculated by the liquid drop model. Another subpopulation (Sub-B) of the tested neutrophils displayed three deformation phases: a first one reflecting the rapid entry of cell into the micropipette, a second with constant deformation rate, and a third phase, with a slower, also constant, deformation rate were recorded. The corresponding apparent viscosities were found as μapp-second-Phase(NSub-B) = 341 ± 94 Pa·s and μapp-third-Phase(NSub-B) = 1651 ± 734 Pa·s. The apparent viscosity values of the neutrophilic nucleus, μapp (Nnucl) = 2468 ± 1345 Pa·s and of the whole neutrophil calculated in the third phase of deformation, μapp-third-Phase(NSub-B) = 1651 ± 734 Pa·s were comparable. These results support our hypothesis that the nucleus plays a significant role in the mechanical and rheological behavior of the neutrophil, especially when it has to pass through openings much smaller than its size.
Keywords: Deformability, neutrophil, micropipette, microcirculation, liquid drop model
