Selective dielectrophoretic array formation of unmodified B cells through microparticle modification of non-target cells

Dielectrophoresis (DEP) has been applied as an external force for discriminating and separating target cells from heterogeneous cell populations. Separation and collection of target cells are important processes for downstream single-cell analysis. Here, we report the array formation of target cells by selectively applying positive DEP (p-DEP) to target cells. DEP is unsuitable for separating cells with similar electrical properties because of their similar DEP behavior. Thus, non-target cells were modified with particles exhibiting DEP behavior different from that of the cells. The resulting cell-particle complexes exhibited DEP trapping behavior different from that of unmodified cells. We applied this approach to demonstrate the separation of B cells from mouse splenocytes. Splenocytes containing target B cells and bead-modified non-target cells were introduced into a fluidic channel with microwell array electrodes. B cells were trapped in the microwells by p-DEP upon application of an AC voltage at 700 kHz, whereas cell-bead complexes showed reduced stable p-DEP trapping and predominantly flowed downstream through the channel. B cells accounted for 26% of the original splenocyte population, as determined by immunofluorescence analysis. In a reconstituted 1 : 1 mixture of the B-cell-enriched fraction and bead-modified non-B-cell fraction, B-cell microwell occupancy reached approximately 70% within 10 min. These results demonstrate the selective array formation of unmodified target B cells under conditions in which cell-bead complexes exhibited reduced stable p-DEP trapping, suggesting the potential of this approach for the selective separation and array formation of target cells from heterogeneous cell populations.