Blood cells circulate in a dynamic fluidic environment, and during hematologic processes such as hemostasis, thrombosis, and inflammation, blood cells interact biophysically with a myriad of vascular matrices—blood clots and the subendothelial matrix. While it is known that adherent cells physiologically respond to the mechanical properties of their underlying matrices, how blood cells interact with their mechanical microenvironment of vascular matrices remains poorly understood. To that end, we developed microfluidic systems that achieve high fidelity, high resolution, single-micron PDMS features that mimic the physical geometries of vascular matrices. With these electron beam lithography (EBL)-based microsystems, the physical interactions of individual blood cells with the mechanical properties of the matrices can be directly visualized. We observe that the physical presence of the matrix, in and of itself, mediates hematologic processes of the three major blood cell types: platelets, erythrocytes, and leukocytes. First, we find that the physical presence of single micron micropillars creates a shear microgradient that is sufficient to cause rapid, localized platelet adhesion and aggregation that leads to complete microchannel occlusion; this response is enhanced with the presence of fibrinogen or collagen on the micropillar surface. Second, we begin to describe the heretofore unknown biophysical parameters for the formation of schistocytes, pathologic erythrocyte fragments associated with various thrombotic microangiopathies (poorly understood, yet life-threatening blood disorders associated with microvascular thrombosis). Finally, we observe that the physical interactions with a vascular matrix is sufficient to cause neutrophils to form procoagulant neutrophil extracellular trap (NET)-like structures. By combining electron beam lithography (EBL), photolithography, and soft lithography, we thus create microfluidic devices that provide novel insight into the response of blood cells to the mechanical microenvironment of vascular matrices and have promise as research-enabling and diagnostic platforms.

中文翻译：

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在单微米水平上探查血液学过程的血液细胞力学

血细胞在动态的流体环境中循环，在止血，血栓形成和炎症等血液学过程中，血细胞与多种血管基质（血凝块和内皮下基质）进行生物物理性相互作用。虽然已知贴壁细胞在生理上对其下层基质的机械特性作出反应，但是血细胞如何与其血管基质的机械微环境相互作用仍然知之甚少。为此，我们开发了微流体系统，该系统可实现高保真，高分辨率的单微米PDMS功能，可模拟血管基质的物理几何形状。使用这些基于电子束光刻（EBL）的微系统，可以直接可视化单个血细胞与基质机械性能的物理相互作用。我们观察到，基质本身的物理存在本身介导了三种主要血细胞类型的血液学过程：血小板，红细胞和白细胞。首先，我们发现单个微米微柱的物理存在会产生剪切微梯度，足以引起快速，局部的血小板粘附和聚集，从而导致完全的微通道阻塞。微纤毛表面上存在纤维蛋白原或胶原蛋白时，这种反应会增强。其次，我们开始描述迄今未知的血吸虫形成，与各种血栓性微血管病相关的病理性红细胞片段的生物物理参数（人们普遍了解，但与微血管血栓形成有关的危及生命的血液疾病）。最后，我们观察到与血管基质的物理相互作用足以引起嗜中性粒细胞形成促凝性嗜中性粒细胞细胞外陷阱（NET）样结构。通过结合电子束光刻（EBL），光刻和软光刻，我们创建了微流控设备，这些设备可提供对血细胞对血管基质机械微环境的反应的新颖见解，并有望作为研究支持和诊断平台。