Computational modeling of bio-fluid mechanics of white blood cells

Abstract

ABSTRACT The white blood cell is a soft biomaterial that exhibits unique behavior when exposed to the action of a flowing fluid. This behavior often determines the structure-function relationships of the cell-fluid system and gives information on many important processes taking place in living systems. The equilibrium behavior of leukocytes in solvent is relatively well known, but their dynamics is not yet investigated extensively. In the present thesis, the cell is modeled as a viscous fluid that moves in a surrounding less viscous fluid. The dynamics of large-scale deformations of the leukocytes in a given flow field is investigated. In particular; the micro-pipette aspiration of leukocytes is analyzed; and the adhesion dynamics of leukocytes to ligand-coated surfaces is modeled and simulated within the framework of finite-difference/front-tracking methodology. The events such as attachment, detachment, and rolling of leukocytes in shear flow are analyzed. The nucleus of the white blood cell is modeled as a compound drop and uniformly distributed linear springs are used between the nucleus and the cortex to model the effects of the internal structures such as microtubles and microfilaments in the cytoplasm. The new model allows both co-centric and off-centric configurations of the nucleus and cortex; and it is fully reversible, i.e., the cell restores to its initial undeformed configuration when the external forces are removed. Keywords: Cell Deformation, Micro-pipette aspiration, Cell Adhesion, Eront-tracking. IV