Abstract
Droplet microfluidics can form and process millions of picoliter droplets with speed and ease, allowing the execution of huge numbers of biological reactions for high-throughput studies. However, at the conclusion of most experiments, the emulsions must be broken to recover and analyze their contents. This is usually achieved with demulsifiers, like perfluorooctanol and chloroform, which can interfere with downstream reactions and harm cells. Here, we describe a simple approach to rapidly and efficiently break microfluidic emulsions, which requires no chemicals. Our method allows one-pot multi-step reactions, making it useful for large scale automated processing of reactions requiring demulsification. Using a hand-held antistatic gun, we pulse emulsions with the electric field, coalescing ∼100 μl of droplets in ∼10 s. We show that while emulsions broken with chemical demulsifiers exhibit potent PCR inhibition, the antistatic-broken emulsions amplify efficiently. The ability to break emulsions quickly without chemicals should make our approach valuable for most demulsification needs in microfluidics.
Highlights
Droplet microfluidics performs biological assays by partitioning samples into picoliter aqueous droplets suspended in carrier oil
Microfluidic techniques have advanced beyond forming droplets; they can merge, picoinject, and sort them, in an order customized to the specific task
We have demonstrated a simple method to break microfluidic emulsions using a hand-held antistatic gun
Summary
Droplet microfluidics is a rapidly growing subfield of microfluidics in which picolitervolume droplets are used for applications in biology, chemistry, and physics. Though simple, the technology is amazingly general, with applications in systems biology (genetic interaction studies and single cell transcriptomics), synthetic biology (enzyme and microbe evolution), structural biology (protein crystallization and sequence-function mapping), microbiology (rare cell cultivation and sequencing), tissue engineering (hydrogel encapsulation and cell delivery), and as general analytical tools (digital droplet PCR, digital ELISA, and nucleic acid cytometry). All of these applications leverage the ability of microfluidic devices to form, merge, inject, analyze, and sort huge numbers of droplets quickly and efficiently. In addition, recent advances have boosted throughput further, increasing droplet generation to megahertz and droplet sorting to over 30 kHz, providing unprecedented potential for characterizing systems comprehensively.1932-1058/2017/11(4)/044107/6VC Author(s) 2017.044107-2 Karbaschi, Shahi, and AbateBiomicrofluidics 11, 044107 (2017)droplets, making them unstable. Some demulsifiers, can be partially soluble in aqueous phases, where they can interact with hydrophobic residues of important compounds, like proteins. The technology is amazingly general, with applications in systems biology (genetic interaction studies and single cell transcriptomics), synthetic biology (enzyme and microbe evolution), structural biology (protein crystallization and sequence-function mapping), microbiology (rare cell cultivation and sequencing), tissue engineering (hydrogel encapsulation and cell delivery), and as general analytical tools (digital droplet PCR, digital ELISA, and nucleic acid cytometry).. The technology is amazingly general, with applications in systems biology (genetic interaction studies and single cell transcriptomics), synthetic biology (enzyme and microbe evolution), structural biology (protein crystallization and sequence-function mapping), microbiology (rare cell cultivation and sequencing), tissue engineering (hydrogel encapsulation and cell delivery), and as general analytical tools (digital droplet PCR, digital ELISA, and nucleic acid cytometry).11–14 All of these applications leverage the ability of microfluidic devices to form, merge, inject, analyze, and sort huge numbers of droplets quickly and efficiently.. They can inhibit cell growth and biological reactions, especially involving enzymes. A superior method for recovering the contents of aqueous droplets would quickly break an emulsion without the need of chemicals
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