Department of Biomedical Engineering, Tulane University, New Orleans, LA 70118, USA.
Lab Chip. 2011 Oct 7;11(19):3231-40. doi: 10.1039/c1lc20293f. Epub 2011 Aug 17.
Traffic of leukocytes in microvascular networks (particularly through arteriolar bifurcations and venular convergences) affects the dynamics of capillary blood flow, initiation of leukocyte adhesion during inflammation, and localization and development of atherosclerotic plaques in vivo. Recently, a growing research effort has been focused on fabricating microvascular networks comprising artificial vessels with more realistic, rounded cross-sections. This paper investigated the impact of the cross-sectional geometry of microchannels on the traffic of leukocytes flowing with human whole blood through a non-symmetrical bifurcation that consisted of a 50 μm mother channel bifurcating into 30 μm and 50 μm daughter branches. Two versions of the same bifurcation comprising microchannels with rectangular and rounded cross-sections were fabricated using conventional multi-layer photolithography to produce rectangular microchannles that were then rounded in situ using a recently developed method of liquid PDMS/air bubble injection. For microchannels with rounded cross-sections, about two-thirds of marginated leukocytes traveling along a path in the top plane of the bifurcation entered the smallest 30 μm daughter branch. This distribution was reversed in microchannels with rectangular cross-sections--the majority of leukocytes traveling along a similar path continued to follow the 50 μm microchannels after the bifurcation. This dramatic difference in the distribution of leukocyte traffic among the branches of the bifurcation can be explained by preferential margination of leukocytes towards the corners of the 50 μm mother microchannels with rectangular cross-sections, and by the additional hindrance to leukocyte entry created by the sharp transition from the 50 μm mother microchannel to the 30 μm daughter branch at the intersection. The results of this study suggest that the trajectories of marginated leukocytes passing through non-symmetrical bifurcations are significantly affected by the cross-sectional geometry of microchannels and emphasize the importance of using microfludic systems with geometrical configurations closely matching physiological configurations when modeling the dynamics of whole blood flow in the microcirculation.
白细胞在微血管网络中的流动（特别是通过动脉分支和静脉汇合处）会影响毛细血管血流的动力学、炎症过程中白细胞黏附的启动，以及体内动脉粥样硬化斑块的定位和发展。最近，越来越多的研究致力于制造具有更真实、圆形横截面的人工血管的微血管网络。本文研究了微通道的横截面几何形状对白细胞与人体全血流动通过非对称分叉的影响，该分叉由一个 50μm 的母通道分叉成 30μm 和 50μm 的子分支组成。使用传统的多层光刻技术制造了两种具有矩形和圆形横截面的相同分叉的版本，以产生矩形微通道，然后使用最近开发的液体 PDMS/气泡注入原位将其圆形化。对于具有圆形横截面的微通道，大约三分之二沿分叉顶部平面行进的边缘白细胞进入最小的 30μm 子分支。在具有矩形横截面的微通道中，沿类似路径行进的大多数白细胞在分叉后继续沿 50μm 微通道行进。这种分支中白细胞流动分布的显著差异可以通过边缘白细胞优先向具有矩形横截面的 50μm 母微通道的角部迁移来解释，并且由于从 50μm 母微通道到 30μm 子分支在交点处的急剧过渡，白细胞进入的额外阻碍。这项研究的结果表明，通过非对称分叉的边缘白细胞的轨迹会受到微通道的横截面几何形状的显著影响，并强调了在模拟微循环中全血流动动力学时使用几何形状与生理配置紧密匹配的微流控系统的重要性。
