Mody Nipa A, King Michael R
Departments of Chemical Engineering and Biomedical Engineering, University of Rochester, Rochester, New York 14627, USA.
Langmuir. 2007 May 22;23(11):6321-8. doi: 10.1021/la0701475. Epub 2007 Apr 7.
We used the platelet adhesive dynamics computational method to study the influence of Brownian motion of a platelet on its flow characteristics near a surface in the creeping flow regime. Two important characterizations were done in this regard: (1) quantification of the platelet's ability to contact the surface by virtue of the Brownian forces and torques acting on it, and (2) determination of the relative importance of Brownian motion in promoting surface encounters in the presence of shear flow. We determined the Peclet number for a platelet undergoing Brownian motion in shear flow, which could be expressed as a simple linear function of height of the platelet centroid, H from the surface Pe (platelet) = . (1.56H + 0.66) for H > 0.3 microm. Our results demonstrate that at timescales relevant to shear flow in blood Brownian motion plays an insignificant role in influencing platelet motion or creating further opportunities for platelet-surface contact. The platelet Peclet number at shear rates >100 s-1 is large enough (>200) to neglect platelet Brownian motion in computational modeling of flow in arteries and arterioles for most practical purposes even at very close distances from the surface. We also conducted adhesive dynamics simulations to determine the effects of platelet Brownian motion on GPIbalpha-vWF-A1 single-bond dissociation dynamics. Brownian motion was found to have little effect on bond lifetime and caused minimal bond stressing as bond rupture forces were calculated to be less than 0.005 pN. We conclude from our results that, for the case of platelet-shaped cells, Brownian motion is not expected to play an important role in influencing flow characteristics, platelet-surface contact frequency, and dissociative binding phenomena under flow at physiological shear rates (>50 s(-1)).
我们使用血小板黏附动力学计算方法，研究了在蠕动流状态下血小板的布朗运动对其在表面附近流动特性的影响。在这方面进行了两项重要表征：（1）根据作用于血小板的布朗力和扭矩，量化血小板与表面接触的能力；（2）确定在存在剪切流的情况下，布朗运动在促进表面接触方面的相对重要性。我们确定了在剪切流中做布朗运动的血小板的佩克莱数，它可以表示为血小板质心距表面高度H的简单线性函数，对于H>0.3微米，佩克莱数（血小板）=（1.56H + 0.66）。我们的结果表明，在与血液中剪切流相关的时间尺度上，布朗运动在影响血小板运动或为血小板 - 表面接触创造更多机会方面作用不显著。在剪切速率>100 s-1时，血小板佩克莱数足够大（>200），以至于在动脉和小动脉血流的计算模型中，即使在非常靠近表面的距离，对于大多数实际目的而言，也可以忽略血小板的布朗运动。我们还进行了黏附动力学模拟，以确定血小板布朗运动对GPIbalpha-vWF-A1单键解离动力学的影响。发现布朗运动对键寿命影响很小，并且由于计算得出的键断裂力小于0.005 pN，所以引起的键应力最小。我们从结果中得出结论，对于血小板形状的细胞，在生理剪切速率（>50 s(-1)）下的流动中，布朗运动预计不会在影响流动特性、血小板 - 表面接触频率和解离结合现象方面发挥重要作用。
