Microfluidic droplet detection and sorting
The present invention relates to the field of microfluidics and in particular to methods for detecting microfluidic droplets and particles within droplets, as well as sorting the droplets. These methods allow for quantifying properties and activities of the particles within the droplets. For this purpose, the invention provides microfluidic droplets comprising suitably labelled particles. The invention also provides microfluidic devices and systems having properties which make them particularly suitable for use in the methods of the invention.
1. A microfluidic droplet comprising a first particle associated with an amount of a first detectable label, and a potential particle binding partner associated with an amount of a second detectable label, wherein the amount of the first detectable label is known and/or substantially identical to the amount of the first detectable label associated with a further particle comprised in a further microfluidic droplet, wherein the first detectable label is different from the second detectable label, and wherein the further microfluidic droplet is comprised in a plurality of microfluidic droplets also comprising said microfluidic droplet comprising said first particle, and
wherein the potential particle binding partner is one of an antibody, antibody derivative, antibody mimetic, a bacteriophage, an mRNA-polypeptide complex, an mRNA-ribosome-polypeptide complex, a cell, a virus, a peptide, a protein, a nucleic acid, an aptamer and a small molecule.
2. The microfluidic droplet of claim 1 , wherein the first particle is associated with the second detectable label via binding to the potential particle binding partner.
3. The microfluidic droplet of claim 1 , wherein the first and further particle are selected from the group consisting of a cell, a virus, a bead, a protein and a nanoparticle.
4. The microfluidic droplet of claim 1 , wherein the microfluidic droplet further comprises, associated with an amount of a third detectable label, (i) a particle non-binder or (ii) a second particle not binding the potential particle binding partner.
5. A method for quantifying the binding between a particle and a potential particle binding partner in a microfluidic droplet according to claim 1 , comprising the steps of
(i) measuring the signal of the first detectable label,
(ii) measuring the signal of the second detectable label, and
(iii) normalizing the signal of the second detectable label using the signal of the first detectable label,
wherein the normalized signal of the second detectable label represents the quantity of binding between the particle and the potential particle binding partner.
6. A method for screening potential particle binding partners, comprising the steps of:
(a) feeding a microfluidic droplet comprising a potential particle binding partner-producing cell and a reporter cell into a detection channel, the detection channel comprising a detection point, and wherein the reporter cell signals the effect of a potential particle binding partner produced by the potential particle binding partner-producing cell via a second detectable label, and wherein the reporter cell further comprises a first detectable label, and
(b) detecting a first detectable label and the second detectable label of the reporter cell, comprised in the microfluidic droplet at the detection point, and
(c) normalizing the signal of the second detectable label using the signal of the first detectable label,
wherein the potential particle binding partner is one of an antibody, antibody derivative, antibody mimetic, a bacteriophage, an mRNA-polypeptide complex, an mRNA-ribosome-polypeptide complex, a cell, a virus, a peptide, a protein, a nucleic acid, an aptamer and a small molecule.
7. The method according to claim 6 , further comprising constricting at least the vertical movement of said cells within the microfluidic droplet at least at the detection point in the detection channel, compared to the same microfluidic droplet when having a spherical shape.
8. The method according to claim 6 , further comprising step (d) sorting the microfluidic droplet according to the normalized signal.
9. The method according to claim 6 , further comprising a preparation step (a′) before step (a), comprising the encapsulation of the potential particle binding partner-producing cell and reporter cell into the microfluidic droplet and incubating the potential particle binding partner-producing cell and the reporter cell for an amount of time sufficient for secretion of antibodies inside the droplets.
10. A method for quantifying the effect of a potential particle binding partner on a particle in a microfluidic droplet according to claim 1 , comprising the steps of
(i) measuring the signal of the first detectable label,
(ii) measuring the signal of the second detectable label, and
(iii) normalizing the signal of the second detectable label using the signal of the first detectable label,
wherein the normalized signal of the second detectable label represents the quantity of effect of the potential particle binding partner on the particle.
11. The method according to claim 10 , wherein the particle is a reporter cell, and wherein the reporter cell signals by the second detectable label the effect of the particle binding partner on the reporter cell.