Droplet microfluidic technology for single-cell high-throughput 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.cell encapsulation ͉ viability assay ͉ lab-on-a-chip ͉ emulsion ͉ optical coding

Droplet confinement and leakage: Causes, underlying effects, and amelioration strategies

“…In this respect, a model PDMS microfluidic device was designed within which droplets could be subjected to common microfluidic operations ( Figure S1 in supplementary material 28 ). These include formation at a T-junction, 29 mixing in a channel motif designed to induce chaotic advection, 30 droplet release into a larger chamber 29 (to assess the effect of close proximity and reduced flow rates), droplet exit from the chamber 31 (to assess the effect of increased flow rates and compression), and storage in a large chamber containing a pillar network 32 (to assess the effect of "open" versus "confined" storage conditions). Experiments were performed with a range of oils and surfactants that are commonly used in microfluidic systems, including FC-40, FC-770, mineral oil, silicone oil, decane, hexadecane, and soybean oil, and EA surfactant, Span 80 and ABIL EM 90, amongst others.…”

Encapsulation of single cells into monodisperse droplets by fluorescence-activated droplet formation on a microfluidic chip

“…In addition to compartmentalizing reactions, droplet-based microfluidics can also be used to encapsulate prokaryotic [14][15][16][17][18] and eukaryotic cells [19][20][21][22][23], and even the embryos of multicellular organisms [24,25], which opens up a new avenue for cell analysis. Recently, Brouzes et al [19] developed a droplet-based viability assay that permitted quantitative analysis of cell viability and growth within compartmentalized aqueous droplets.…”

“…Recently, Brouzes et al [19] developed a droplet-based viability assay that permitted quantitative analysis of cell viability and growth within compartmentalized aqueous droplets. By encapsulating human monocytic U937 cells, they screened a drug library for its cytotoxic effect against the U937 cells.…”

Single cell kinase signaling assay using pinched flow coupled droplet microfluidics

“…In fact, cells randomly distributed in a suspension followed the Poisson encapsulation statistics showing low encapsulation rate $0.24% in a physiological solution with cell density $10 4 cells/ml. 20,25 Highly efficient single cell encapsulation has been demonstrated using inertial migration in both a straight channel 26 (56.5% single cell to multiple cells/droplet ratio) and a spiral channel 27 ($77% encapsulation efficiency). In addition, hydrodynamic self-sorting of single cells have also been demonstrated to have a high encapsulation efficiency with successful encapsulation and sorting of 70%-80% of the injected cell population.…”

“…The capillary electrophoresis system was automatized to analyze $3.5 cells/min. [4][5][6][7][8][9][10] Compared with these methods, the droplet based technology is attractive [11][12][13][14][15][16][17][18][19][20][21] because of its ultra high throughput cell encapsulations ($1000 droplets/s) [22][23][24] and accurate fluidic controls. Accordingly, a wide range of droplet base single cell polymerase chain reactions (PCR) were carried out in previous studies.…”