Direct numerical simulation of detachment of single captured leukocyte under different flow conditions

Antibody-based cell isolation using microfluidics finds widespread applications in disease diagnostics and treatment monitoring at point of care (POC) for global health. However, the lack of knowledge on underlying mechanisms of cell capture greatly limits their developments. To address this, in this study, we developed a mathematical model using a direct numerical simulation for the detachment of single leukocyte captured on a functionalized surface in a rectangular microchannel under different flow conditions. The captured leukocyte was modeled as a simple liquid drop and its deformation was tracked using a level set method. The kinetic adhesion model was used to calculate the adhesion force and analyze the detachment of single captured leukocyte. The results demonstrate that the detachment of single captured leukocyte was dependent on both the magnitude of flow rate and flow acceleration, while the latter provides more significant effects. Pressure gradient was found to represent as another critical factor promoting leukocyte detachment besides shear stress. Cytoplasmic viscosity plays a much more important role in the deformation and detachment of captured leukocyte than cortex tension. Besides, better deformability (represented as lower cytoplasmic viscosity) noteworthy accelerates leukocyte detachment. The model presented here provides an enabling tool to clarify the interaction of target cells with functional surface and could help for developing more effective POC devices for global health.