Hybridization chain reaction amplification for in situ imaging
The present invention relates to the use of fluorescently labeled nucleic acid probes to identify and image analytes in a biological sample. In the preferred embodiments, a probe is provided that comprises a target region able to specifically bind an analyte of interest and an initiator region that is able to initiate polymerization of nucleic acid monomers. After contacting a sample with the probe, labeled monomers are provided that form a tethered polymer. Triggered probes and self-quenching monomers can be used to provide active background suppression.
1. A method for forming a structure comprising hybridized nucleic acid monomers, the method comprising:
providing a first hairpin monomer comprising:
a first domain comprising a first sticky end, wherein the first sticky end is available to hybridize to an initiator that comprises a nucleic acid sequence complementary to the first domain;
a single stranded loop; and
a second domain, wherein a portion of the second domain is complementary to a portion of the first domain;
providing a second hairpin monomer comprising:
a first domain comprising a first sticky end, wherein the first sticky end comprises a nucleic acid sequence complementary to a portion of the second domain of the first monomer;
a single stranded loop; and
a second domain, wherein a portion of the second domain is hybridized to a portion of the first domain; and
combining the first and second monomers with the initiator,
wherein the initiator hybridizes to the first domain of the first monomer, and subsequently the first domain of the second monomer hybridizes to the second domain of the first monomer, thereby forming a structure comprising the first and second monomers.
2. The method of claim 1 , wherein the second domain of the first hairpin monomer comprises a portion of the single stranded loop.
3. The method of claim 1 , wherein the first hairpin monomer further comprises a third domain, wherein a portion of the third domain is hybridized to a portion of the first domain prior to hybridization of the initiator to the first domain of the first monomer.
4. The method of claim 3 , additionally comprising providing a third nucleic acid monomer, wherein the third domain of the first hairpin monomer is capable of hybridizing to a first domain of the third nucleic acid monomer.
5. The method of claim 4 , wherein the first domain of the third nucleic acid monomer comprises a first sticky end that is capable of hybridizing to the portion of the third domain of the first hairpin monomer that is hybridized to the portion of the first domain prior to hybridization of the initiator to the first domain of the first monomer.
6. The method of claim 1 , wherein the first monomer is labeled with a fluorophore.
7. The method of claim 6 , wherein the first monomer is labeled with a fluorescence quencher.
8. The method of claim 1 , wherein the second monomer is labeled with a fluorophore.
9. The method of claim 1 , wherein the first monomer is labeled with a first fluorophore and the second monomer is labeled with a second fluorophore.
10. The method of claim 9 , wherein the first and second fluorophores are different.
11. The method of claim 9 , wherein at least one of the first and second fluorophores is quenched prior to forming the structure.
12. The method of claim 1 , wherein the initiator is an analyte in a biological sample.
13. The method of claim 12 , wherein the analyte is mRNA.
14. The method of claim 1 , wherein the initiator is part of a detection probe.
15. The method of claim 14 , wherein the initiator is only made available to hybridize to the first domain of the first monomer when the detection probe is bound to an analyte of interest.