High-throughput continuous dielectrophoretic separation of neural stem cells.

Developing new means of enriching specific stem cell populations that have beneficial properties for treating disease is crucial for optimizing cell-based therapies. We found a novel way to sort stem cells that is label-free, which is ideal for therapeutic purposes since labels can alter cell function or disrupt efficient transplantation. However, initial means of cell separation were low throughput and did not yield sufficient numbers of cells needed for human applications. To address this, we developed a new cell sorting platform that can continually sort stem cells, greatly increasing the numbers of enriched cells. We created an integrated small volume (microfluidic) cell separation system that incorporates two distinct modules to facilitate high-throughput continuous cell separation. The first module (hydrophoresis) consists of a serpentine channel with ridges and trenches to generate a diverging fluid flow that focuses cells into two streams along the channel edges. The second module (dielectrophoresis) is composed of a chevron-shaped electrode array. Separation in the dielectrophoresis module is driven by inherent cell properties and does not require cell-type-specific labels. The chevron shape of the electrode array couples with fluid flow in the channel to enable continuous sorting of cells to increase throughput. We tested the new system with neural stem cells since their inherent electrophysiological properties reflect their differentiation capacity (e.g., whether they will mature into astrocytes or neurons). The goal of our experiments was to enrich cells that will form astrocytes. Sorting parameters were optimized for each batch of neural stem cells to ensure effective and consistent separations. The continuous sorting design of the device significantly improved sorting throughput and reproducibility. Sorting yielded two cell fractions, and we found that astrocyte-biased cells were enriched in one fraction and depleted from the other. This is an advantage of the new continuous sorting device over traditional dielectrophoresis-based sorting platforms that target a subset of cells for enrichment but do not provide a corresponding depleted population. The new cell separation system improves label-free cell sorting by increasing throughput and delivering enriched and depleted cell subpopulations in a single sort.