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RESEARCH PAPERS: Papers on Cell Biomechanics

Rapid Flow of Passive Neutrophils Into a 4 μm Pipet and Measurement of Cytoplasmic Viscosity

[+] Author and Article Information
D. Needham, R. M. Hochmuth

Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27706

J Biomech Eng 112(3), 269-276 (Aug 01, 1990) (8 pages) doi:10.1115/1.2891184 History: Received November 05, 1989; Revised May 15, 1990; Online March 17, 2008

Abstract

Neutrophils from five different individuals are isolated with a density separation technique. A total of 151 unactivated (passive) cells are rapidly aspirated at constant suction pressure and at room temperature into a pipet with a diameter of 4 μm. The suction pressures in excess of an initial yield threshold are 0.5, 1 and 2 kPa and are comparable to those encountered in the microcirculation. These pressures are well in excess of the small suction pressure of ~ 20 Pa that is required to form a static hemispherical bump on the cell. At a given aspiration pressure, the leading edge of an individual cell is “tracked” as it flows into the pipet. A theory based on the flow of a Newtonian liquid from either a hemisphere or a spherical segment into a cylinder is used to model the entry process. Both theory and experiment show that during most of the entry process the leading edge of the cell moves at a nearly constant velocity with a rapid acceleration at the end. For cells from five different individuals at the three different excess aspiration pressures, Newtonian theory gives a cytoplasmic viscosity of 135 ± 54 Pa·s and overall entry times of 3.3s (0.5 kPa), 1.6s (1 kPa) and 0.82s (2 kPa). These results and those of Evans and Yeung at lower aspiration pressures indicate that the complex cytoplasm inside unactivated neutrophils behaves as a nearly Newtonian fluid with a viscosity on the order of 102 Pa·s over almost a two order of magnitude range in aspiration pressure and, thus, rate of deformation.

Copyright © 1990 by The American Society of Mechanical Engineers
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