Gravitational effect on the cell in bio-fluid suspension

Abstract

The fascination with space and human spaceflight has significantly increased in recent years. Nevertheless, microgravity has a significant impact on humans. Immune and red blood cells utilize hematic or lymphatic streams (bio-fluid) as their primary mode of transport, and these streams have been identified as a significant concern under microgravity. This study aims to quantitatively address the puzzle of how cells are influenced by gravity when they are suspended in bio-fluid. The Dissipative Particle Dynamics (DPD) approach was used to model blood and the cell by applying gravity as an external force along the vertical axis and varied from 0g to 2g during parameter sweeps. It was observed that the cell undergoes shape change and spatially aligns under the influence of gravity, and this was quantified with metrics such as Elongation and Deformation indices, pitch angle, and normalized center of mass. The Elongation Index increased linearly, and the normalized center of mass declined linearly with the applied gravity. Correlation analysis showed a strong correlation between applied gravity and the aforementioned variables. Forces exerted on the solid, specifically drag, shear stress, and solid forces, declined in magnitude as the gravitational force exerted on the cell was increased. Further analysis showed that increasing gravity affected the cell velocity, leading to extended proximity near the wall and increased viscous interaction with the surrounding fluid particles, triggering a shape change. This study marks a significant step in understanding gravity effects on blood cells.