Fig. 5
Measurement of migration of neutrophil-like HL-60 cells with the microfluidic device placed in a stage incubator controlled at 5% CO2. (a) Representative phase-contrast microscopy images of neutrophil-like HL-60 cells before and after the 3-h experiment under a pH gradient, and migration trajectories of neutrophil-like HL-60 cells over the period. (b) Temporal and spatial variations in average migration speed of the cells under the pH gradient (mean ± S.D., n = 3). (c) Stacked bar chart of migration speed in the subdivided regions A1–A5 between 2 and 3 h after the experiment under the pH gradient. (d) Spatial variation in average migration speed of the cells between 2 and 3 h after the experiment under the uniform pH conditions and the pH gradient and (e) variation in the migration speed with pH (mean ± S.D., n = 3). (f) Box-and-whisker plots of persistence of the migration direction between 2 and 3 h after the experiment under the uniform pH conditions and the pH gradient. The upper and lower extremes represent the 90th and 10th percentiles, the box plot represents quartiles, and the open square and circle inside each box show the average and the median values, respectively. The variables cL and cR indicate the CO2 concentration in the gas mixtures supplied to the left and right gas channels, respectively. Significant differences in persistence were assessed by the Kruskal–Wallis test followed by Dunn’s post-hoc test. **P < 0.01; ***P < 0.001.
