External force-assisted cell positioning inside microfluidic devices.

This paper describes straightforward approaches to positioning cells within microfluidic devices that can be implemented without special equipment or fabrication steps. External forces can effectively transport and position cells in preferred locations inside microfluidic channels. Except for centrifugal force-based positioning that can be used with any microfluidic channels, hydrodynamic and gravitational force-based positioning yield reproducible and biocompatible results when implemented with a microfluidic "module" that contains a barrier with embedded microgrooves. Primary rat cortical neurons, metastatic human breast cancer cells MDA-MB-231, NIH 3T3 mouse fibroblasts, and human umbilical vein endothelial cells (HUVECs) were compatible with the positioning processes. After positioning, cells attached, proliferated and migrated like control cells that were cultured on tissue culture dishes or glass coverslips. No apparent morphological differences were observed in positioned cells compared with control cells. Finally, to demonstrate a practical application of the methods, cells were placed in a single row along a wall inside a microfluidic chemotaxis chamber (MCC), and were exposed to stable concentration gradient of chemoattractant. Cell positioning allows that all cells get exposed to the same level of chemoattractant at the start of the experiment helping standardize cellular response.