Dielectrophoretic sorting on a microfabricated flow cytometer: Label free separation of Babesia bovis infected erythrocytes

Dielectrophoresis is a method that has demonstrated great potential in cell discrimination and isolation. In this study, the dielectrophoretic sorting of normal and Babesia bovis infected erythrocytes was performed using a microfabricated flow cytometer. Separation was possible through exploitation of the dielectric differences between normal and infected erythrocytes, essentially due to the higher ionic membrane permeability of B. bovis infected cells. Sorting experiments were performed inside a microchip made from Pt microelectrodes and SU-8 channels patterned on a glass substrate. Optimum cell separation was achieved at 4 MHz using an in vitro culture of B. bovis suspended in 63 mS/m phosphate buffer and applying a sinusoidal voltage of 15 V peak-to-peak. Normal erythrocytes experienced stronger positive dielectrophoresis (pDEP) than B. bovis infected cells, moving them closer to the microelectrodes. Under these conditions it was possible to enrich the fraction of infected cells from 7 to 50% without the need of extensive sample preparation or labelling. Throughout the experiments very few microliters of sample were used, suggesting that this system may be considered suitable for integration in a low-cost automated device to be used in the in situ diagnostic of babesiosis.