Systematic dielectrophoretic analysis of the Ara-C-induced NB4 cell apoptosis combined with gene expression profiling.

Dielectrophoresis (DEP) can be used to noninvasively measure the dielectric state of the cell, and this data can be used to monitor cell health or apoptosis. In this study, we followed events associated with cytosine arabinoside (Ara-C)-induced apoptosis in NB4 cells using DEP analysis. Our data showed that the membrane capacitance of NB4 cells decreases from 9.42 to 7.63 mF/m(2) in the first 2 hours following treatment with Ara-C, and that this decreased capacitance persists for >12 hours. Additionally, cytoplasmic conductivity decreases from 0.217 to 0.190 S/m within 2 hours of Ara-C treatment; this level is maintained for a short period of time before decreasing. We also investigated these events molecularly at the level of gene expression using microarray analysis and showed that the expression of genes related to membrane capacitance and cytoplasmic conductivity change dramatically as early as 2 hours post-Ara-C treatment, and further demonstrated a temporal relationship between the dielectric properties and key events in apoptosis. This study, integrating physical electrical properties of the cell membrane and cytoplasm with those of conductivity-related gene networks, provides new insights into the molecular mechanisms underlying the initiation of apoptosis, establishing a systematic foundation for DEP application in follow-up drug screening and development of medicines for treating leukemia.