Microfabricated crossflow devices and methods
A microfluidic device for analyzing and/or sorting biological materials (e.g., molecules such as polynucleotides and polypeptides, including proteins and enzymes; viruses and cells) and methods for its use are provided. The device and methods of the invention are useful for sorting particles, e.g. virions. The invention is also useful for high throughput screening, e.g. combinatorial screening. The microfluidic device comprises a main channel and an inlet region in communication with the main channel at a droplet extrusion region. Droplets of solution containing the biological material are deposited into the main channel through the droplet extrusion region. A fluid different from and incompatible with the solution containing the biological material flows through the main channel so that the droplets containing the biological material do not diffuse or mix. Biological material within the droplets can be analyzed and/or sorted by detecting a predetermined characteristic of the biological sample in each droplet and sorting the droplet accordingly.
1. A method of conducting reactions in a droplet on a microfluidic device, comprising:
(a) introducing first microfluidic droplets into an extrusion fluid, wherein the first microfluidic droplets contain a first sample fluid, said first sample fluid comprises a first biological material, and the first sample fluid is immiscible with the extrusion fluid;
(b) introducing second microfluidic droplets into the extrusion fluid, wherein the second microfluidic droplets contain a second sample fluid, said second sample fluid comprises a second biological material, and the second sample fluid is immiscible with the extrusion fluid; and
(c) combining individual first sample fluid droplets with individual second sample fluid droplets thereby producing a plurality of combined droplets, wherein the first biological material a first material in the first droplets interacts with the second biological material in at least one combined droplet;
wherein step (a) comprises flowing the extrusion fluid through an inlet channel while flowing the first sample fluid through another inlet channel towards a junction that is constructed and arranged so that microfluidic droplets of the first sample fluid are introduced into the extrusion fluid; and
wherein step (b) comprises flowing the extrusion fluid through an inlet channel while flowing the second sample fluid through another inlet channel towards a junction that is constructed and arranged so that microfluidic droplets of the second sample fluid are introduced into the extrusion fluid.
2. The method of claim 1 , wherein the first biological material is an enzyme, a polynucleotide, or a polypeptide.
3. The method of claim 2 , wherein the first biological material is an enzyme and the second biological material is a substrate of the enzyme.
4. The method of claim 3 , wherein the second sample fluid droplets contain on average, no more than one particle or molecule of the second biological material per fluid droplet.
5. The method of claim 1 , wherein the detectable signal is produced from a polymerase chain reaction.
6. A method for carrying out an enzymatic reaction in a microfluidic device, comprising:
(a) introducing a first microfluidic droplet comprising an aqueous solution into an extrusion fluid, wherein the aqueous solution is immiscible in the extrusion fluid, and wherein the first microfluidic droplet contains an enzyme;
(b) introducing a second microfluidic droplet containing an aqueous solution into the extrusion fluid, wherein the second microfluidic droplet contains a substrate of said enzyme, wherein at least one of the first and second microfluidic droplets contains a reporter molecule that produces a detectable signal in response to a reaction catalyzed by the enzyme on the substrate;
(c) combining the first and second droplets under conditions in which the reaction catalyzed by the enzyme on the substrate occurs, thereby generating the detectable signal; and
(d) detecting the detectable signal;
wherein step (a) comprises flowing the extrusion fluid through an inlet channel while flowing a first sample fluid containing the enzyme through another inlet channel towards a junction that is constructed and arranged so that microfluidic droplets of the first sample fluid are introduced into the extrusion fluid; and
wherein step (b) comprises flowing the extrusion fluid through an inlet channel while flowing a second sample fluid containing the substrate through another inlet channel towards a junction that is constructed and arranged so that microfluidic droplets of the second sample fluid are introduced into the extrusion fluid.
7. A method of conducting a reaction in a microfluidic device, comprising:
(a) extruding first microfluidic droplets by flowing a first sample fluid immiscible with an extrusion fluid through an inlet into said extrusion fluid flowing through a first channel of the device;
(b) extruding second microfluidic droplets by flowing a second sample fluid immiscible with the extrusion fluid through an inlet into said extrusion fluid flowing through a second channel of the device; and
(c) combining microfluidic droplets extruded in step (a) with microfluidic droplets extruded in step (b) such that material from the first droplets interact with material from the second droplets.
8. The method of claim 7 , wherein a material in the first microfluidic droplets and/or the second microfluidic droplets is an enzyme, a polynucleotide, or a polypeptide.
9. The method of claim 7 , wherein a material in the first microfluidic droplets is an enzyme and a material in the second microfluidic droplets is a substrate for the enzyme.
10. The method of claim 9 , wherein the first and second droplets are combined in step (c) under conditions where the enzyme catalyzes a reaction of the substrate.
11. The method of claim 7 , wherein the first or second sample fluid droplets contain on average no more than one particle or molecule per fluid droplet.
12. The method of claim 7 , which is a method for conducting a polymerase chain reaction.
13. The method of claim 7 , wherein the first and second channels carrying extrusion fluid are the same channel.
14. The method of claim 7 , wherein the first and second channels carrying extrusion fluid are different channels.
15. The method of claim 7 , wherein the first and second sample fluids comprise an aqueous buffer.
16. The method of claim 7 , wherein the extrusion fluid is an oil or non-polar solvent.
17. The method of claim 7 , wherein the first and second droplets in the extrusion fluid tend to conform to the size and shape of the channel.
18. The method of claim 7 , wherein the first and second droplets are monodisperse.