Reduced chemotactic migration of polymorphonuclear neutrophil (PMN) in sepsis patients leads to decreased bacterial clearance and accelerates the progression of sepsis disease. Quantification of PMN chemotaxis in sepsis patients can help characterize the immune health of sepsis patients. Microfluidic microarrays have been widely used for cell chemotaxis analysis because of the advantages of low reagent consumption, near-physiological environment, and visualization of the migration process. Currently, the study of PMN chemotaxis using microfluidic chips is mainly limited by the cumbersome cell separation operation and low throughput of microfluidic chips. In this paper, we first designed an inertial cell sorting chip to achieve label-free separation of the two major cell types by using the basic principle that leukocytes (mainly granulocytes, lymphocytes and monocytes) and erythrocytes move to different positions of the spiral microchannel when they move in the spiral microchannel under different strength of inertial force and Dean's resistance. Subsequently, in this paper, we designed a multi-channel cell migration chip and constructed a microfluidic PMN inertial label-free sorting and chemotaxis analysis platform. The inertial cell sorting chip separates leukocyte populations and then injects them into the multi-channel cell migration chip, which can complete the chemotaxis test of PMN to chemotactic peptide (fMLP) within 15 min. The remaining cells, such as monocytes with slow motility and lymphocytes that require pre-activation with proliferative culture, do not undergo significant chemotactic migration. The test results of sepsis patients ( n=6) and healthy volunteers ( n=3) recruited in this study showed that the chemotaxis index (CI) and migration velocity ( v) of PMN from sepsis patients were significantly weaker than those from healthy volunteers. In conclusion, the microfluidic PMN inertial label-free sorting and chemotaxis analysis platform constructed in this paper can be used as a new tool for cell label-free sorting and migration studies.
脓毒症患者中性粒细胞（PMN）的趋化迁移能力减弱，导致细菌清除率下降，加速了脓毒症病程的发展。对脓毒症患者PMN的趋化性进行量化，有助于表征脓毒症患者的免疫健康状况。微流控芯片具有试剂消耗低、近生理环境、迁移过程可视化等优点，被广泛用于细胞趋化性分析。目前，采用微流控芯片进行PMN趋化性的研究，主要受限于细胞分离操作繁琐和微流控芯片通量低。本文首先设计了一款惯性细胞分选芯片，利用白细胞（主要包括粒细胞、淋巴细胞和单核细胞）和红细胞在螺旋微通道中运动时，会受到不同大小惯性力和迪恩阻力的作用，而移动至螺旋微通道的不同位置聚焦这一基本原理，实现两大类细胞无标记分离。随后，本文设计了多通道细胞迁移芯片，构建了微流控PMN惯性无标记分选及趋化性分析平台，惯性细胞分选芯片分离出白细胞群后注入多通道细胞迁移芯片，可在15 min内完成PMN对趋化肽（fMLP）的趋化性测试。其余细胞，如单核细胞运动缓慢、淋巴细胞需要预先激活与增殖培养，而不会发生明显趋化迁移现象。本研究招募的脓毒症患者（ n = 6）和健康志愿者（ n = 3）测试结果表明，脓毒症患者PMN的趋化性指数（CI）和迁移速度（ v）明显弱于健康志愿者。综上，本文构建的微流控PMN惯性无标记分选及趋化性分析平台可以作为细胞无标记分选及迁移研究的新工具。.
Keywords: Microfluidic chip; Polymorphonuclear neutrophil; Sepsis; Sorting; chemotaxis.