In vitro cytokine expression analysis by droplet microfluidics

Abstract

Droplet microfluidics provides a miniaturized platform to conduct biological assays. We previously developed a droplet microfluidic chip assay for screening cancer cells against chemical drugs and chimeric antigen receptor T (CAR-T) cells, respectively. In this study, we investigated chip application on a cytokine expression assay using MCF7 breast cancer reporter cells engineered by fusing green fluorescent protein (GFP) to the C-terminus of endogenous interleukin-6 (IL6) gene. Combined tumor necrosis factor (TNF) treatment and serum-free medium starvation stimulated IL6-GFP expression and enhanced GFP fluorescence. Our data showed that on-chip assay recapitulates the cellular response in vitro, although absolute quantification of IL6 induction could not be accomplished. The demonstration of multi-timepoint IL6 expression analysis paves the way for our future study on tumor response to immune attack via cytokine signaling.