Objective: To solve the problems of low throughput of current cell migration research methods，which was difficult to establish a stable concentration gradient and observe cell migration behavior in real time，a six-channel array microfluidic chip was designed in this paper． Methods : In this paper，a six-channel array microfluidic chip is designed．Firstly，multiphysics modeling and numerical simulation were performed using the finite element analysis software COMSOL Multiphysics 5．5 to analyze the flow behavior of the main pipeline of cell migration. Then，the throughput advantage of the device was verified by testing the chemotaxis response of healthy human neutrophils to different types of chemokine gradients in this microfluidic chip．Subsequently，by analyzing the migration rate of neutrophils in 6 patients with type II diabetes mellitus and 3 healthy people，the clinical applicability of the annular six-channel array microfluidic chip was further verified．Finally，the Pearson coefficient was used to analyze the correlation between neutrophil chemotaxis function and some physiological indicators in patients with diabetes. Results: The concentration gradient data inside the pipeline simulated by the simulation software was compatible with the real-time fluorescence test data of the pipeline．The average migration rate of healthy human neutrophils was (0．21 ± 0．01 ) μm / s in 100 nmol / L interleukin-8 ( IL-8 ) environment and (0．22 ± 0．01 ) μm / s in 100 nmol / L N-Formyl-Met-Leu-Phe ( fMLP) environment． In the comparison of neutrophil migration experiments between healthy people and diabetic patients，the chemotaxis rate of neutrophils in healthy people was (0．19 ± 0．01) μm / s ，and the neutrophil chemotaxis rate in diabetic patients was (0. 15 ± 0. 02 ) μm / s． Correlation analysis showed that neutrophil migration rate in patients with type II diabetes mellitus was inversely correlated with glycated hemoglobin． Conclusion The high-throughput microfluidic chip proposed in this paper allowed rapid and selective detection of cell migration characteristics at the single-cell level，and it could be used as a new tool for cell migration research.

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.
Humans ; Chemotaxis ; Neutrophils/metabolism* ; Microfluidics ; Cell Movement ; Sepsis/metabolism*