A sheath-less electric impedance micro-flow cytometry device for rapid label-free cell classification and viability testing

Abstract

Microfluidic electric impedance flow cytometry (IFC) chips have strong advantages over the traditional flow cytometry system because they are self-contained, disposable, economic in reagent consumption, and easier to operate. However, the throughput, sensitivity, and simplicity of the microfluidic IFC chips are inversely related to one another, and their reported impedance-based cell differentiation capability is in general limited. In this paper, we designed a sheath-less microfluidic IFC chip with a constriction structure between the detection electrodes to enhance the particle sensing performance, and built the entire sensing system around it, including the sensing circuit and data processing software. The measurement of the volume, limit of detection (∼3 μm), coefficient variation (6.83%) and other characteristics of the device was performed using the standard polymer beads. This sheath-less polydimethylsiloxane microfluidic device had a simple structure, which could maintain a single-cell sequence flow at the detection area, and displayed high signal-to-noise ratio (23.5–32.6 dB) and low coincidence ratio signals for further analysis. The throughput of the chip for single-cell screening can reach up to 172 cells per s, and thus, 10 000 cells could be analyzed in a few minutes for statistical analysis. Moreover, the electrical conductance and susceptance were found to be good at differentiating the bead/cell sizes and membrane/surface characteristics of cells/beads, respectively. These parameters were used to classify the population of a large amount of drug-treated cells (>10 000 cells per sample), displaying good performance in distinguishing apoptotic/necrotic cells from live cells. The ratios of apoptotic, necrotic, and live cells analyzed using our system were consistent with the traditional flow cytometry results (R² = 0.9796). Along with the miniaturization of the electric sensing circuit, our system can be applicable for novel, compact and easy operative (single) cell analysis systems in the future.