Chemotaxis Assay of RAW264.7 Cells Using a Simple Microfluidic Chip with Lipopolysaccharide Gradient

A microfluidic chip with two inlets, a cell chamber, and one outlet was fabricated for chemotaxis analysis of cells. Aqueous phases with or without fluorescent dyes were separately injected into the cell chamber through inlets to confirm the concentration gradient. Profiles of the concentration gradient were simply controlled by changing the flow rate. RAW264.7, an immune cell, was selected as a model cell line to evaluate chemotaxis. Cell migration in the chamber was quantitatively analyzed over time by injecting an aqueous phase containing lipopolysaccharide into one inlet. It was found that RAW264.7 at a high lipopolysaccharide concentration migrated chaotically in all directions. However, RAW264.7 at a low lipopolysaccharide concentration migrated towards the higher lipopolysaccharide concentration at a velocity of 0.98 µm/h. Such concentration-gradient microfluidic chip fabricated in this study can be used as a platform to analyze the behavior of various cells in response to specific chemicals.