A microfluidic microwell device for immunomagnetic single-cell trapping

Single-cell analysis has been widely applied in various biomedical applications, such as cancer diagnostics, immune status monitoring, and drug screening. To perform an accurate and rapid cellular analysis, various magnetic-activated cell sorting techniques are available in the markets. However, large sample requirement and uneven magnetic field distribution limit its application in single-cell trapping and following analysis. To address these problems, we developed a microfluidic microwell device for immunomagnetic single-cell trapping. By adding a microwell layer between the microchannel and magnet, the magnetic field along the device becomes more uniform. Besides, magnetic beads can be retained in the array of microwell after the high-speed washing step, whereas untrapped beads would be flushed away, resulting in high single-particle trapping efficiency (62%) and purity (99.6%). To achieve large-area single-cell trapping, we introduced a “sweeping” loading protocol to further expand the single-particle trapping range. In the microwell region near to the edge of the magnet, over 3000 single magnetic beads were trapped in a 10 mm2 area. Finally, we demonstrated immunomagnetic-labeled THP-1 cells can successfully be trapped at single-cell level in the microwell. The cell trapping process can be done in 10 min. We believe the platform with an accurate and efficient single-cell trapping functionality could potentially be used for various cellular analyses at the single-cell level.