Assay kits

1. A kit for detecting an analyte of interest in a sample comprising, in one or more vials, containers, or compartments:

a) a surface comprising (i) a capture reagent for the analyte, and (ii) an anchoring reagent comprising an anchoring oligonucleotide, wherein the capture reagent and the anchoring reagent are immobilized on the surface;

b) a detection reagent for the analyte that is linked to a nucleic acid probe, wherein the nucleic acid probe is capable of being extended to form an extended sequence comprising an anchoring oligonucleotide complement, wherein the anchoring oligonucleotide complement is complementary to the anchoring oligonucleotide; and

c) a template oligonucleotide that is capable of hybridizing to the nucleic acid probe and that comprises a first region comprising a same sequence as the anchoring oligonucleotide.

2. The kit of claim 1 , wherein the surface comprises a particle.

3. The kit of claim 1 , wherein the surface comprises a well of a multi-well plate.

4. The kit of claim 3 , wherein the well comprises a plurality of distinct binding domains and the capture reagent and the anchoring reagent are located on two distinct binding domains within the well.

5. The kit of claim 3 , wherein the well comprises a plurality of distinct binding domains and the capture reagent and the anchoring reagent are located on the same binding domain within the well.

6. The kit of claim 1 , wherein the surface comprises a plurality of distinct binding domains and the capture reagent and the anchoring reagent are located on two distinct binding domains on the surface.

7. The kit of claim 1 , wherein the surface comprises a plurality of distinct binding domains and the capture reagent and the anchoring reagent are located on the same binding domain on the surface.

8. The kit of claim 1 , wherein the surface comprises an electrode.

9. The kit of claim 1 , wherein the capture reagent is selected from a group consisting of an antibody, an antigen, a ligand, a receptor, an oligonucleotide, a hapten, an epitope, a mimotope, and an aptamer.

10. The kit of claim 1 , wherein the detection reagent is selected from the group consisting of an antibody, an antigen, a ligand, a receptor, an oligonucleotide, a hapten, an epitope, a mimotope, and an aptamer.

11. The kit of claim 1 , wherein the capture reagent and the detection reagent are both antibodies to the analyte.

12. The kit of claim 1 , further comprising a buffer, a polymerase, a ligase, a labeled or unlabeled dNTP, a detectable label, a co-reactant for a detectable label, a blocking agent, a stabilizing agent, a detergent, a salt, a pH buffer, a preservative, a labeled probe, an assay diluent, a calibrator, or a combination thereof.

13. The kit of claim 1 , wherein the analyte of interest comprises an exosome.

14. The kit of claim 13 , wherein the detection reagent is a first detection reagent linked to a first nucleic acid probe, and wherein the kit further comprises a second detection reagent linked to a second nucleic acid probe.

15. The kit of claim 14 , wherein the capture reagent, the first detection reagent, and the second detection reagent are antibodies to a target molecule in or on a surface of the exosome.

16. The kit of claim 15 , wherein the capture reagent is capable of binding to a common exosome target protein selected from one or more of CD9, CD63, CD81, Hsp70, PDCD6IP, and Tsg101.

17. The kit of claim 15 , wherein at least one of the first detection reagent and the second detection reagent is an antibody to a disease-specific target molecule in or on the surface of the exosome.

18. The kit of claim 15 , wherein the first detection reagent and the second detection reagent each binds to one of a pair of interacting exosome target molecules.

19. The kit of claim 18 , wherein the pair of interacting exosome target molecules comprise a ligand-receptor pair, an mRNA and an RNA-binding protein, or both.

20. The kit of claim 1 , wherein the template oligonucleotide further comprises a second region comprising a detection oligonucleotide complement, wherein the extended sequence further comprises a detection oligonucleotide, and wherein the kit further comprises a labeled probe that comprises (i) a same sequence as the detection oligonucleotide complement and that is capable of binding to the detection oligonucleotide; and (ii) a detectable label.

21. A kit for detecting an analyte of interest in a sample comprising, in one or more vials, containers, or compartments:

a) a capture reagent for the analyte, wherein the capture reagent is capable of being immobilized to a surface,

b) an anchoring reagent comprising an anchoring oligonucleotide, wherein the anchoring reagent is capable of being immobilized to a surface;

c) a detection reagent for the analyte that is linked to a nucleic acid probe, wherein the nucleic acid probe is capable of being extended to form an extended sequence comprising an anchoring oligonucleotide complement, wherein the anchoring oligonucleotide complement is complementary to the anchoring oligonucleotide; and

d) a template oligonucleotide that is capable of hybridizing to the nucleic acid probe and that comprises a first region comprising a same sequence as the anchoring oligonucleotide.

22. The kit of claim 21 , further comprising the surface to which the capture reagent and the anchoring reagent are capable of being immobilized.

23. The kit of claim 22 , wherein the surface comprises a particle.

24. The kit of claim 22 , wherein the surface comprises a well of a multi-well plate.

25. The kit of claim 24 , wherein the well comprises a plurality of distinct binding domains, and the capture reagent and the anchoring reagent are located on two distinct binding domains on the well.

26. The kit of claim 24 , wherein the well comprises a plurality of distinct binding domains, and the capture reagent and the anchoring reagent are located on the same binding domain on the well.

27. The kit of claim 22 , wherein the surface comprises a plurality of distinct binding domains, and the capture reagent and the anchoring reagent are located on two distinct binding domains on the surface.

28. The kit of claim 22 , wherein the surface comprises a plurality of distinct binding domains, and the capture reagent and the anchoring reagent are located on the same binding domain on the surface.

29. The kit of claim 22 , wherein the surface comprises an electrode.

30. The kit of claim 22 , wherein each of the capture reagent and the detection reagent is independently selected from a group consisting of an antibody, an antigen, a ligand, a receptor, an oligonucleotide, a hapten, an epitope, a mimotope, and an aptamer.

31. The kit of claim 21 , wherein each of the capture reagent and the detection reagent is an antibody to the analyte.

32. The kit of claim 21 , further comprising a buffer, a polymerase, a ligase, a labeled or unlabeled dNTP, a detectable label, a co-reactant for a detectable label, a blocking agent, a stabilizing agent, a detergent, a salt, a pH buffer, a preservative, a labeled probe, an assay diluent, a calibrator, or a combination thereof.

33. The kit of claim 21 , wherein the analyte of interest comprises an exosome.

34. The kit of claim 33 , wherein the detection reagent is a first detection reagent linked to a first nucleic acid probe, and wherein the kit further comprises a second detection reagent linked to a second nucleic acid probe.

35. The kit of claim 34 , wherein the capture reagent, the first detection reagent, and the second detection reagent are antibodies to a target molecule in or on a surface of the exosome.

36. The kit of claim 35 , wherein the capture reagent is capable of binding to a common exosome target protein selected from one or more of CD9, CD63, CD81, Hsp70, PDCD6IP, and Tsg101.

37. The kit of claim 35 , wherein at least one of the first detection reagent and the second detection reagent is an antibody to a disease-specific target molecule in or on the surface of the exosome.

38. The kit of claim 35 , wherein the first detection reagent and the second detection reagent each binds to one of a pair of interacting exosome target molecules.

39. The kit of claim 38 , wherein the pair of interacting exosome target molecules comprise a ligand-receptor pair, an mRNA and an RNA-binding protein, or both.

40. The kit of claim 21 , wherein the template oligonucleotide further comprises a second region comprising a detection oligonucleotide complement, wherein the extended sequence further comprises a detection oligonucleotide, and wherein the kit further comprises a labeled probe that comprises (i) a same sequence as the detection oligonucleotide complement and that is capable of binding to the detection oligonucleotide; and (ii) a detectable label.