Label-free Monitoring of the Neutrophil Differentiation Progress of Hl60 Cells Using Microcapillary Electrophoresis Chips

To exploit the application of the on-chip cell electrophoresis system to the monitoring of the progress of cellular differentiation, the temporal change in the electrophoretic mobility (EPM) of human promyelocytic leukemia cell lines (HL60) during neutrophil differentiation was systematically investigated. Firstly, to confirm the action of two differentiation inducers, all-trans retinoic acid (ATRA) and dimethyl sulfoxide (DMSO), the cells were subjected to WrightGiemsa staining and observed by light microscopy for morphologically classification 2, 4, and 6 days after initiation of differentiation. The differentiated cells showed a gradual progress of differentiation. Subsequently, the EPM of the cells prepared under the same conditions described above was measured using an on-chip cell electrophoresis system. The EPM also showed a gradual change with the progress of differentiation. To clarify the relationship between differentiational state and EPM, the experimental data were analyzed by principal component analysis (PCA). There is a strong correlation between the percentage of cells classified morphologically as metamyelocytes, band neutrophils and segmented neutrophils and the percentage of cells whose EPMs were between −0.5×10 and −1.1×10 cm V s (P=0.95). The present result demonstrated the feasibility of the on-chip EPM measurement system as a label-free monitoring tool for cell differentiation.