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Sorting of 15 and 7 micrometer diameter bead using a microfluidic platform

Many research applications call for sorting and isolating cells from a heterogeneous cell mixture. The expanding need to isolate rare cells such as circulating tumor cells (CTCs) from blood samples increases the demand for cell sorting devices. As opposed to conventional instrumentation, microfluidic devices are easy to use, smaller, versatile, and affordable. 

Passive cell sorting systems do not require labeling steps nor additional external power (e.g. electrical field), which makes them attractive. Channels with spiral shapes are used to separate particles according to their size based on the Dean forces. The main benefit of this design is high throughput (>1.5 mL/min). Fluigent and microfluidic ChipShop validated an effective and commercial solution for cell sorting. 

To demonstrate the separation of particle mixtures, a solution containing 7.5 µm and 15 µm diameter polystyrene particles labeled with FITC, and TRITC fluorophores respectively was used. The particle streams were viewed and captured separately using appropriate filter cubes.

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MATERIALS AND METHODS

LINK
Connect to Fluigent software

LINK Connect to Fluigent software

FLOW EZ 7bar
Pressure controller

Flow EZ pressure controller Lineup

FLOW UNIT L & XL
Flow sensor

FLOW UNIT Fluigent flow sensor flow meter to monitor flow rate

SPIRAL SORTER CHIP
microfluidic ChipShop Device

SORTING cell chip

P-CAP
Pressurized reservoirs

Fluigent P-CAP air-tight metal cap pressurized reservoir with falcon tube

STARTING SORTING EXPERIMENTS

The 7.3 µm and 15.25 µm fluorescent microbeads are mixed and diluted in DI water before testing to reach a concentration of ~1.105 beads/mL. The Flow EZ is connected to the reservoir containing the mixture using a P-CAP. The reservoir is connected to the inlet of the microfluidic device using tubing of 500 µm inner diameter (ID). Tubing passes through the Flow Unit to control and monitor flow rate. Tubing is connected to the outlets of the microfluidic device to recover the beads. The flow rate is set using the Flow EZ. Here, sorting units 2 and 3 with flow rates of respectively 1.5 mL/min and 150 µL/min are used. The particle streams were viewed and captured separately using TRITC and FITC filter cubes. 

RESULTS

The 7.3 µm and 15.25 µm fluorescent microbeads are mixed and diluted in DI water before testing to reach a concentration of ~1.105 beads/mL. The Flow EZ is connected to the reservoir containing the mixture using a P-CAP. The reservoir is connected to the inlet of the microfluidic device using tubing of 500 µm inner diameter (ID). Tubing passes through the Flow Unit to control and monitor flow rate. Tubing is connected to the outlets of the microfluidic device to recover the beads. The flow rate is set using the Flow EZ. Here, sorting units 2 and 3 with flow rates of respectively 1.5 mL/min and 150 µL/min are used. The particle streams were viewed and captured separately using TRITC and FITC filter cubes. 

cell sorting

CONCLUSION

In this application note, we introduced a commercially-available microfluidic system to perform passive size separation of a microparticle mixture. The system includes a spiral-shaped microfluidic device from microfluidic ChipShop and pressure-based flow controllers from Fluigent. Tuning Dean and lift forces induced by spiral microchannels allow to obtain distinct particle streams and subsequently sort particles according to their sizes. Beads with diameters of 15 and 7.3 µm were successfully sorted using flow rates of 150 µL/min and 1.5 mL/min. We provide an easy to use, versatile, and cost-effective solution for particle size sorting.

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