Balsara Hiren D, Banton Rohan J, Eggleton Charles D
Department of Mechanical Engineering, University of Maryland, Baltimore County, Baltimore, MD, 21250, USA.
US Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD, USA.
Biomech Model Mechanobiol. 2016 Oct;15(5):1055-68. doi: 10.1007/s10237-015-0742-5. Epub 2015 Nov 13.
Understanding, manipulating and controlling cellular adhesion processes can be critical in developing biomedical technologies. Adhesive mechanisms can be used to the target, pattern and separate cells such as leukocytes from whole blood for biomedical applications. The deformability response of the cell directly affects the rolling and adhesion behavior under viscous linear shear flow conditions. To that end, the primary objective of the present study was to investigate numerically the influence of capsule membrane's nonlinear material behavior (i.e. elastic-plastic to strain hardening) on the rolling and adhesion behavior of representative artificial capsules. Specifically, spherical capsules with radius of [Formula: see text] were represented using an elastic membrane governed by a Mooney-Rivlin strain energy functions. The surfaces of the capsules were coated with P-selectin glycoprotein-ligand-1 to initiate binding interaction with P-selectin-coated planar surface with density of [Formula: see text] under linear shear flow varying from 100 to [Formula: see text]. The numerical model is based on the Immersed Boundary Method for rolling of deformable capsule in shear flow coupled with Monte Carlo simulation for receptor/ligand interaction modeled using Bell model. The results reveal that the mechanical properties of the capsule play an important role in the rolling behavior and the binding kinetics between the capsule contact surface and the substrate. The rolling behavior of the strain hardening capsules is relatively smoother and slower compared to the elastic-plastic capsules. The strain hardening capsules exhibits higher contact area at any given shear rate compared to elastic-plastic capsules. The increase in contact area leads to decrease in rolling velocity. The capsule contact surface is not in complete contact with the substrate because of thin lubrication film that is trapped between the capsule and substrate. This creates a concave shape on the bottom surface of the capsule that is referred to as a dimple. In addition, the present study demonstrates that the average total bond force from the capsules lifetime increases by 37 % for the strain hardening capsules compared to elastic-plastic capsules at shear rate of [Formula: see text]. Finally, the model demonstrates the effect of finite membrane deformation on the coupling between hydrodynamic and receptor/ligand interaction.
理解、操纵和控制细胞粘附过程对于开发生物医学技术至关重要。粘附机制可用于靶向、图案化和分离细胞，如从全血中分离白细胞，以用于生物医学应用。细胞的变形性响应直接影响粘性线性剪切流条件下的滚动和粘附行为。为此，本研究的主要目的是数值研究胶囊膜的非线性材料行为（即从弹塑性到应变硬化）对代表性人工胶囊滚动和粘附行为的影响。具体而言，半径为[公式：见原文]的球形胶囊用由穆尼 - 里夫林应变能函数控制的弹性膜表示。胶囊表面涂有P - 选择素糖蛋白配体 - 1，以便在100至[公式：见原文]的线性剪切流下，与密度为[公式：见原文]的P - 选择素包被的平面表面引发结合相互作用。该数值模型基于用于剪切流中可变形胶囊滚动的浸入边界方法，并结合了使用贝尔模型建模的受体/配体相互作用的蒙特卡罗模拟。结果表明，胶囊的力学性能在滚动行为以及胶囊接触表面与底物之间的结合动力学中起着重要作用。与弹塑性胶囊相比，应变硬化胶囊的滚动行为相对更平滑且更慢。在任何给定剪切速率下，应变硬化胶囊比弹塑性胶囊表现出更高的接触面积。接触面积的增加导致滚动速度降低。由于夹在胶囊和底物之间的薄润滑膜，胶囊接触表面并未与底物完全接触。这在胶囊底表面形成了一个凹形，称为凹坑。此外，本研究表明，在[公式：见原文]的剪切速率下，与弹塑性胶囊相比，应变硬化胶囊在其整个生命周期内的平均总结合力增加了37%。最后，该模型展示了有限膜变形对流体动力学与受体/配体相互作用之间耦合的影响。
