Droplet microfluidic technology for single-cell high-throughput screening

TLDR

The authors present and validate a droplet‑based microfluidic technology for high‑throughput screening of single mammalian cells, demonstrated through a cytotoxicity assay on U937 cells. The platform encapsulates individual cells and reagents in 1 pL–10 nL aqueous droplets within an immiscible oil, enabling digital manipulation, a droplet viability assay for quantitative scoring, and an optically coded droplet library for composition identification during read‑out. The system maintained high viability of U937 cells over four days, successfully screened a drug library for cytotoxic effects, and proved modular, robust, and free of moving parts, making it suitable for diverse high‑throughput single‑cell analyses and combinatorial screening.

Abstract

We present a droplet-based microfluidic technology that enables high-throughput screening of single mammalian cells. This integrated platform allows for the encapsulation of single cells and reagents in independent aqueous microdroplets (1 pL to 10 nL volumes) dispersed in an immiscible carrier oil and enables the digital manipulation of these reactors at a very high-throughput. Here, we validate a full droplet screening workflow by conducting a droplet-based cytotoxicity screen. To perform this screen, we first developed a droplet viability assay that permits the quantitative scoring of cell viability and growth within intact droplets. Next, we demonstrated the high viability of encapsulated human monocytic U937 cells over a period of 4 days. Finally, we developed an optically-coded droplet library enabling the identification of the droplets composition during the assay read-out. Using the integrated droplet technology, we screened a drug library for its cytotoxic effect against U937 cells. Taken together our droplet microfluidic platform is modular, robust, uses no moving parts, and has a wide range of potential applications including high-throughput single-cell analyses, combinatorial screening, and facilitating small sample analyses.