This microfluidic chip enables cell sorting in 16 μs; the enlarged view shows a demonstration of on-chip cell sorting of a Euglena gracilis cell (time interval of each frame: 40 μs). (Image copyright: Shinya Sakuma, Yusuke Kasai, Takeshi Hayakawa, and Fumihito Arai)

Recognizing that sorting of individual cells is necessary for many biological applications, including isolation of specific cell types from cell suspensions, researchers at Nagoya University (Japan) have developed a high-speed cell sorting method for large cells with high viability using dual on-chip pumps.

Fluorescence-activated cell sorting (FACS) has been used for high-throughput cell sorting. In this method, lasers are used to excite auto-fluorescence or tagged fluorescence of cells included in droplets, and then droplets are diverted into different containers depending on their characteristics. However, FACS of larger cells requires samples to be processed under low pressure through wider nozzles to prevent damage, so sorting is limited to low-level throughput.

So, the researchers used a microfluidic chip for cell sorting to prevent sample infection. The chip has microchannels into which cell suspensions are introduced for sorting. The research group integrated two externally driven on-chip pumps into the microfluidic chip for high-speed flow control. Using a high-speed actuator as the driving source of pump, they succeeded in producing a flow with 16 μs for cell sorting.

The microfluidic chip contains a cross-shaped sorting area and three-branched microfluidic channel. “Target/non-target cells are three-dimensionally aligned in the main channel,” says corresponding author Shinya Sakuma. “When target cells are detected, the on-chip pumps work rapidly to sort cells into one of two interest channels. Meanwhile, non-target cells are flushed into the waste channel without pump actuation.”

The technique can sort large and small cells with high speed, high purity, and high viability. “We tested the method on microalgae as an example of large cells, around 100 μm in size, and achieved 95.8% purity, 90.8% viability, and a 92.8% success rate,” says corresponding co-author Yusuke Kasai. “As a model small cell type, we used a cancer cell whose size is around 24 μm, and achieved 98.9% purity, 90.7% viability, and a 97.8% success rate.

Source: Bio Optics world