School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, China.
Department of Orthopaedic Oncology, Xi-Jing Hospital, The Fourth Military Medical University, Xi'an, China.
Biomech Model Mechanobiol. 2018 Feb;17(1):223-234. doi: 10.1007/s10237-017-0956-9. Epub 2017 Sep 6.
Cellular adhesion plays a critical role in biological systems and biomedical applications. Cell deformation and biophysical properties of adhesion molecules are of significance for the adhesion behavior. In the present work, dynamic adhesion of a deformable capsule to a planar substrate, in a linear shear flow, is numerically simulated to investigate the combined influence of membrane deformability (quantified by the capillary number) and bond formation/dissociation rates on the adhesion behavior. The computational model is based on the immersed boundary-lattice Boltzmann method for the capsule-fluid interaction and a probabilistic adhesion model for the capsule-substrate interaction. Three distinct adhesion states, detachment, rolling adhesion and firm adhesion, are identified and presented in a state diagram as a function of capillary number and bond dissociation rate. The impact of bond formation rate on the state diagram is further investigated. Results show that the critical bond dissociation rate for the transition of rolling or firm adhesion to detachment is strongly related to the capsule deformability. At the rolling-adhesion state, smaller off rates are needed for larger capillary number to increase the rolling velocity and detach the capsule. In contrast, the critical off rate for firm-to-detach transition slightly increases with the capillary number. With smaller on rate, the effect of capsule deformability on the critical off rates is more pronounced and capsules with moderate deformability are prone to detach by the shear flow. Further increasing of on rate leads to large expansion of both rolling-adhesion and firm-adhesion regions. Even capsules with relatively large deformability can maintain stable rolling adhesion at certain off rate.
细胞黏附在生物系统和生物医学应用中起着至关重要的作用。细胞变形和黏附分子的生物物理特性对黏附行为具有重要意义。在本工作中，数值模拟了可变形囊泡在线性剪切流中与平面基底的动态黏附，以研究膜变形性（用毛细数量化）和键形成/解离速率对黏附行为的综合影响。计算模型基于囊泡-流体相互作用的浸入边界-格子玻尔兹曼方法和囊泡-基底相互作用的概率黏附模型。确定了三种不同的黏附状态，即脱离、滚动黏附和牢固黏附，并在状态图中以毛细数和键解离速率为函数呈现出来。进一步研究了键形成速率对状态图的影响。结果表明，从滚动黏附或牢固黏附到脱离的临界键解离速率与囊泡变形性密切相关。在滚动黏附状态下，为了增加滚动速度并使囊泡脱离，需要较小的脱离速率，而对于较大的毛细数。相比之下，牢固黏附到脱离转变的临界脱离速率随毛细数略有增加。随着键形成速率的减小，囊泡变形性对临界脱离速率的影响更加显著，中等变形性的囊泡更容易受到剪切流的影响而脱离。进一步增加键形成速率会导致滚动黏附区和牢固黏附区的显著扩大。即使是具有较大变形性的囊泡也可以在一定的脱离速率下保持稳定的滚动黏附。
