Systems and methods for transfer of reagents between droplets
The disclosure provides systems and methods for droplet processing. For example, a method can include providing a first droplet and a second droplet. In some cases, the first droplet may have a first concentration of a reagent and the second droplet may have a second concentration of the reagent. The second droplet may comprise a bead or a biological particle. The method can also include subjecting the first droplet and the second droplet to conditions sufficient to transfer the reagent from the first droplet to the second droplet, thereby decreasing the first concentration in the first droplet and increasing the second concentration in the second droplet.
1 . A system for droplet processing, the system comprising:
a partitioning fluid comprising a fluorinated oil and a fluorosurfactant, wherein the fluorosurfactant comprises a perfluoropolyether (PFPE);
a first aqueous fluid comprising an ammonium salt and a surfactant, wherein the surfactant is sodium dodecyl sulfate (SDS); and
a plurality of beads, wherein a bead of the plurality of beads is coupled to a plurality of nucleic acid barcode molecules comprising at least 1,000 nucleic acid barcode molecules;
wherein the partitioning fluid and the first aqueous fluid are capable of forming a first emulsion comprising a first plurality of droplets and a plurality of micelles dispersed in the fluorinated oil, wherein the first plurality of droplets comprises a first droplet, the first droplet comprising the first aqueous fluid and a first droplet surface comprising the fluorosurfactant, and
wherein a micelle of the plurality of micelles is derived from the first droplet and comprises the surfactant;
wherein the partitioning fluid and a second aqueous fluid comprising the plurality of beads and a plurality of cells are capable of forming a second emulsion comprising a second plurality of droplets comprising a second droplet, the second droplet comprising the bead of the plurality of beads, a cell of the plurality of cells, and a second droplet surface comprising the fluorosurfactant; and
wherein the micelle is capable of transferring the surfactant to the second droplet after contacting the first emulsion with the second emulsion.
2 . The system of claim 1 , wherein the fluorosurfactant comprises a carboxylic acid-terminated PFPE.
3 . The system of claim 2 , wherein the fluorosurfactant is a first fluorosurfactant and the partitioning fluid further comprises a second fluorosurfactant.
4 . The system of claim 3 , wherein the second fluorosurfactant is a polyethylene glycol (PEG)-PFPE block copolymer.
5 . The system of claim 3 , wherein the second fluorosurfactant is a PFPE-polyethylene glycol (PEG)-PFPE triblock copolymer.
6 . The system of claim 3 , wherein the first fluorosurfactant or the second fluorosurfactant inhibits droplet coalescence.
7 . The system of claim 1 , wherein the first aqueous fluid further comprises n-dodecyl-beta-D-maltoside (DBDM), sodium lauroyl sarcosinate, t-Octylphenoxypolyethoxyethanol, or polysorbate 20.
8 . The system of claim 1 , wherein the partitioning fluid and the first aqueous fluid are capable of forming the first emulsion when combined and agitated.
9 . The system of claim 8 , wherein the partitioning fluid and the second aqueous fluid are capable of forming the second emulsion when combined and agitated.
10 . The system of claim 1 , wherein a nucleic acid barcode molecule of the plurality of nucleic acid barcode molecules comprises a bead-specific barcode sequence and a sequence capable of hybridizing to a messenger ribonucleic acid (mRNA) of the cell.
11 . The system of claim 10 , wherein the bead is a hydrogel bead.
12 . The system of claim 1 , wherein the micelle of the plurality of micelles further comprises the fluorosurfactant.