Emulsion chemistry for encapsulated droplets
System, including methods, apparatus, compositions, and kits, for making and using a stabilized emulsion. A method of generating a stabilized emulsion is provided. In the method, an aqueous phase may be provided. The aqueous phase may include an effective concentration of one or more skin-forming proteins. An emulsion may be formed. The emulsion may include droplets of a dispersed phase disposed in a continuous phase, with the aqueous phase being the continuous phase or the dispersed phase. The emulsion may be heated to create an interfacial skin between each droplet and the continuous phase, to transform the droplets into capsules.
1. A method of generating skin-encapsulated capsules comprising:
a) providing an aqueous phase comprising:
i) at least one reagent;
ii) at least 0.01% by weight of a skin-forming protein;
b) forming an emulsion comprising droplets of said aqueous phase disposed in a continuous phase comprising an oil and an ionic surfactant;
c) heating said emulsion to at least 50° C. to create an interfacial skin between each droplet and the continuous phase, such that said droplets form skin-encapsulated capsules; and
d) adding a spacing fluid to the emulsion after heating the emulsion, wherein the spacing fluid is miscible with the continuous phase.
2. The method of claim 1 , further comprising picking up capsules of the emulsion with a fluid transport device after the step of adding a spacing fluid.
3. The method of claim 1 , wherein the continuous phase is an oil phase that is used as a continuous phase for forming an emulsion, wherein each of the oil phase and the spacing fluid has a percent by weight of surfactant, and wherein the percent by weight of surfactant in the oil phase is higher than in the spacing fluid.
4. The method of claim 3 , wherein the percent by weight of surfactant in the oil phase is at least ten-fold higher than in the spacing fluid.
5. The method of claim 1 , wherein the continuous phase is an oil phase that is used as a continuous phase for forming an emulsion, wherein the oil phase includes an ionic surfactant and the spacing fluid includes a nonionic surfactant.
6. The method of claim 1 , further comprising (1) driving flow of capsules in a carrier fluid along a flow path extending through a detection region, and (2) the adding of the spacing fluid adds the spacing fluid to the carrier fluid in the flow path thereby spacing capsules before the capsules reach the detection region.
7. The method of claim 6 , wherein each of the oil phase and the spacing fluid has a percent by weight of surfactant, and wherein the percent by weight of surfactant in the oil phase is substantially higher than in the spacing fluid.
8. The method of claim 7 , wherein the percent by weight of surfactant in the oil phase is at least 100-fold higher than in the spacing fluid.
9. The method of claim 1 , wherein no surfactant present in the spacing fluid is at a concentration above the critical micelle concentration of the surfactant.
10. The method of claim 1 , wherein the spacing fluid does not comprise a surfactant.
11. The method according to claim 1 wherein said reagent comprises nucleic acid.
12. The method according to claim 11 wherein said nucleic acid is selected from the group comprising a nucleic acid target, a nucleic acid primer and a nucleic acid probe.
13. The method according to claim 1 wherein said reagent comprises a nucleic acid primer.
14. The method according to claim 1 wherein said reagent comprises a pair of nucleic acid primers.
15. The method according to claim 1 wherein said reagent comprises an amplification mixture comprising at least one primer, at least one probe, a polymerase enzyme and deoxynucleotides.
16. The method according to claim 15 wherein said method further comprises:
a) thermocycling said capsules through multiple rounds of heating and cooling, such that amplicons are formed; and
b) detecting said amplicons.
17. The method according to claim 16 wherein said detecting comprises flowing said capsules through a detection region of a detector.
18. The method according to claim 1 wherein said oil is a fluorinated oil.
19. The method according to claim 18 wherein said ionic surfactant is a negatively charged ionic surfactant.
20. The method according to claim 1 wherein said skin-forming protein is selected from the group comprising albumin, casein, gelatin and globulin.