Method for generating aptamers with improved off-rates
The present disclosure describes the identification and use of aptamers and photoaptamers having slower dissociation rate constants than those obtained using previously described methods. Specifically, the present disclosure describes methods for the identification and use of aptamers to one or more targets within a histological or cytological sample, which have slow rates of dissociation. The aptamers may be used to assess localization, relative density, and presence or absence of one or more targets in cytological and histological samples. Targets may be selected that are specific and diagnostic of a given disease state for which the sample was collected. The aptamers may also be used to introduce target specific signal moieties. In addition to target identification, the aptamers may be used to amplify signal generation through a variety of methods.
1. A method for the diagnosis of a specific disease state in a tissue or cell sample comprising:
(a) contacting a tissue sample or cell sample with an aptamer, wherein the aptamer comprises at least one C-5 modified pyrimidine that increases the dissociation half-life of the aptamer compared to the aptamer without the C-5 modified pyrimidine;
(b) measuring the presence, absence or quantity of the aptamer; and
(c) diagnosing the disease state of the tissue or cell based on the presence, absence or quantity of the aptamer measured.
2. The method of claim 1 , wherein said tissue or cell sample is fixed by a method used for histology or cytology.
3. The method of claim 1 , wherein the aptamer has a dissociation half-life from the target of from about 15 minutes and about 240 minutes.
4. The method of claim 3 , wherein said aptamer has a dissociation half-life from the target selected from the group consisting of a time ≧about 15 minutes, ≧about 30 minutes, ≧about 60 minutes, ≧about 90 minutes, ≧about 120 minutes, ≧about 150 minutes, ≧about 180 minutes, ≧about 210 minutes and ≧about 240 minutes.
5. The method of claim 1 , wherein said aptamer comprises a detectable moiety.
6. The method of claim 5 , wherein said detectable moiety is selected from the group consisting of a dye, a quantum dot, a radiolabel, a electrochemical functional group, an enzyme, an enzyme substrate, a ligand and a receptor.
7. The method of claim 1 , wherein said aptamer is a single-stranded nucleic acid or a double-stranded nucleic acid.
8. The method of claim 7 , wherein said aptamer comprises DNA, RNA, or both DNA and RNA.
9. The method of claim 1 , wherein said aptamer further comprises at least one additional chemical modification.
10. The method of claim 9 , wherein said at least one additional chemical modification is a chemical substitution at one or more positions independently selected from a ribose position, a deoxyribose position, a phosphate position, and a base position.
11. The method of claim 1 , wherein said C-5 modified pyrimidine is independently selected from the group listed in FIG. 14 .
12. The method of claim 11 , wherein said C-5 modified pyrimidine is independently selected from the group consisting of 5-(N-benzylcarboxyamide)-2′-deoxyuridine (BndU), 5-(N-isobutylcarboxyamide)-2′-deoxyuridine (iBudU), 5-(N-tryptaminocarboxyamide)-2′-deoxyuridine (TrpdU) and 5-(N-naphthylmethylcarboxyamide)-2′-deoxyuridine (NapdU).
13. The method of claim 1 , wherein said presence, absence or quantity of the target is a marker indicative of a specific disease state or condition and wherein the presence, absence or quantity of said target in the tissue sample or cell sample provides a basis for the diagnoses of the specific disease state or facilitates selection of, or a decision regarding whether to continue, a therapeutic regimen to treat the specific disease.
14. The method of claim 1 , wherein said target is selected from the group listed in FIG. 8 .
15. The method of claim 14 , wherein said target is selected from the group consisting of prostate specific antigen, CMBK, CEA, CA125, HPV16, HPV18, YKL-40, VEGF, ErbB-1 and HER2.
16. The method of claim 1 , wherein said tissue sample is selected from the group consisting of epithelium tissue, connective tissue, cartilage tissue, bone tissue, muscle tissue, nerve tissue, blood vessel tissue, heart tissue, lymphatic system tissue, respiratory tract tissue, urinary tract tissue, endocrine system tissue, tumor tissue and reproductive system tissue.
17. The method of claim 1 , wherein said cell sample is selected from the group consisting of abdominal and pelvic washings, body cavity fluids (pleural, peritoneal), urine, gastric/esophageal washings, fine needle aspirates (FNA), breast fluid, CSF, cyst fluid, synovial fluid, and bronchial washings.
18. The method of claim 1 , wherein said cell sample is cultured from epithelium tissue, connective tissue, cartilage tissue, bone tissue, muscle tissue, nerve tissue, blood vessel tissue, heart tissue, lymphatic system tissue, respiratory tract tissue, urinary tract tissue, endocrine system tissue, tumor tissue, and reproductive system tissue.
19. The method of claim 1 , wherein said aptamer has a dissociation half-life from said target of greater than or equal to about 30 minutes.
20. The method of claim 10 , wherein said additional chemical modification is independently selected from the group consisting of a 2′-position sugar modification, a 2′-amino (2′-NH 2 ), a 2′-fluoro (2′-F), a 2′-O-methyl (2′-OMe), an 8-position purine modification, a modification at a cytosine exocyclic amine, a substitution of 5-bromouracil, a substitution of 5-bromodeoxyuridine, a substitution of 5-bromodeoxycytidine, a backbone modification, methylation, a 3′ cap, and a 5′ cap.
21. The method of claim 1 , wherein said the aptamer is selected from a slow off-rate enrichment process, wherein the slow off-rate enrichment process is selected from incubation of a candidate mixture with a competitor molecule, dilution of a candidate mixture, or dilution of a candidate mixture in the presence of a competitor molecule.
22. The method of claim 1 , further comprising a kinetic challenge at any point after (a) and before (b).
23. The method of claim 22 , wherein said kinetic challenge comprises diluting the mixture containing the aptamer affinity complex and incubating the mixture containing the aptamer affinity complex for a time selected from the group consisting of greater than or equal to 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 30 minutes and 60 minutes.
24. The method of claim 22 , wherein said kinetic challenge comprises diluting the mixture containing the aptamer affinity complex and incubating the mixture containing the aptamer affinity complex for a time such that the ratio of the measured level of aptamer affinity complex to the measured level of the non-specific complex is increased.
25. The method of claim 22 , wherein said kinetic challenge comprises adding a competitor to the mixture containing the aptamer affinity complex, and incubating the mixture containing the aptamer affinity complex for a time selected from the group consisting of greater than or equal to 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 30 minutes, and 60 minutes.
26. The method of claim 22 , wherein said kinetic challenge comprises adding a competitor to the mixture containing the aptamer affinity complex and incubating the mixture containing the aptamer affinity complex for a time such that the ratio of the measured level of aptamer affinity complex to the measured level of the non-specific complex is increased.
27. The method of claim 22 , wherein said kinetic challenge comprises diluting the mixture containing the aptamer affinity complex, adding a competitor to the mixture containing the aptamer affinity complex, and incubating the mixture containing the aptamer affinity complex for a time selected from the group consisting of greater than or equal to 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 30 minutes, and 60 minutes.
28. The method of claim 22 , wherein said kinetic challenge comprises diluting the mixture containing the aptamer affinity complex, adding a competitor to the mixture containing the aptamer affinity complex and incubating the mixture containing the aptamer affinity complex for a time such that the ratio of the measured level of aptamer affinity complex to the measured level of the non-specific complex is increased.
29. The methods of claim 22 , wherein the kinetic challenge comprises the introduction of a competitor molecule and said competitor molecule is selected from the group consisting of an oligonucleotide, heparin, herring sperm DNA, salmon sperm DNA, dextran sulfate, polyanion, abasic phosphodiester polymer, dNTP, and pyrophosphate.