Fluorescent Sensor and Methods

• US 20090221088A1
• Filed: 08/10/2006
• Published: 09/03/2009
• Est. Priority Date: 08/15/2005
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Snee, Preston T., Somers, Rebecca C., Nocera, Daniel G., Bawendi, Moungi G.
• Granted Patent: US 8,101,430 B2
• Time in Patent Office: Days
• US Class Current: 436/172
• CPC Class Codes: G01N 21/6486 Measuring fluorescence of biological material, e.g. DNA, RNA, cells G01N21/6428 takes precedence
• CPC Class Codes: G01N 33/542 with steric inhibition or signal modification, e.g. fluorescent quenching
• CPC Class Codes: Y10T 436/207497 Molecular oxygen

Abstract

Binding an analyte can cause a change in fluorescence emission of a sensor. The change in fluorescence can be related to the amount of analyte present. The sensor can include a semiconductor nanocrystal linked to a fluorescent moiety. Upon excitation, the fluorescent moiety can transfer energy to the semiconductor nanocrystal, or vice versa.

Claims

1. A composition comprising:

a first fluorescent moiety;

a second fluorescent moiety associated with the first fluorescent moiety;

wherein the first fluorescent moiety is capable of transferring energy to the second fluorescent moiety when excited, and the first fluorescent moiety or the second fluorescent moiety includes a semiconductor nanocrystal.

2. The composition of claim 1, wherein the second fluorescent moiety is capable of binding an analyte.

3. The composition of claim 2, wherein the first fluorescent moiety includes a semiconductor nanocrystal.

4. The composition of claim 2, wherein an emission intensity of the second fluorescent moiety is altered when second fluorescent moiety binds the analyte.

5. The composition of claim 1, wherein the semiconductor nanocrystal includes an outer layer including a compound linked to a surface of the nanocrystal and having a first hydrophobic region.

6. The composition of claim 5, further comprising an amphiphilic compound having a second hydrophobic region interacting with the first hydrophobic region.

7. The composition of claim 6, wherein the amphiphilic compound is linked to the second fluorescent moiety.

8. The composition of claim 7, wherein the amphiphilic compound is linked to a plurality of fluorescent moieties.

9. The composition of claim 1, wherein the semiconductor nanocrystal includes a core including a first semiconductor material.

10. The composition of claim 9, wherein the semiconductor nanocrystal includes an overcoating on a surface of the core including a second semiconductor material.

11. The composition of claim 10, wherein the semiconductor nanocrystal includes an second overcoating on a surface of the overcoating including a third semiconductor material.

12. The composition of claim 1, wherein the semiconductor nanocrystal includes an outer layer including an amphiphilic polymer.

13. The composition of claim 1, wherein the outer layer includes a polyethylene glycol or a dendrimer.

14. The composition of claim 1, wherein the semiconductor nanocrystal includes a ZnSe or CdZnS core.

15. A method of detecting an analyte, comprising:

illuminating a composition with an excitation wavelength, wherein the composition includes;

a first fluorescent moiety;

a second fluorescent moiety associated with the first fluorescent moiety;

wherein the first fluorescent moiety is capable of transferring energy to the second

fluorescent moiety when excited, and the first fluorescent moiety or the second

fluorescent moiety includes a semiconductor nanocrystal; and

measuring a fluorescent emission of the composition.

16. The method of claim 15, wherein the second fluorescent moiety is capable of binding an analyte.

17. The method of claim 16, wherein the first fluorescent moiety includes a semiconductor nanocrystal.

18. The method of claim 16, wherein an emission intensity of the second fluorescent moiety is altered when second fluorescent moiety binds the analyte.

19. The method of claim 15, wherein measuring a fluorescent emission of the composition includes measuring a fluorescence emission intensity at an emission wavelength of the first fluorescent moiety.

20. The method of claim 15, wherein measuring a fluorescent emission of the composition includes measuring a fluorescence emission intensity at an emission wavelength of the second fluorescent moiety.

21. The method of claim 15, wherein measuring a fluorescent emission of the composition includes measuring a ratio of a fluorescence emission intensity of the first fluorescent moiety to a fluorescence emission intensity of the second fluorescent moiety.

23. The method of claim 21, further comprising relating the measured ratio to a concentration of the analyte.

24. The method of claim 15, wherein measuring includes performing single-photon excited fluorescence microscopy or multi-photon laser scanning microscopy.

22. The method of claim 15, wherein measuring a fluorescent emission of the composition includes determining a ratio between a fluorescence emission intensity of the first fluorescent moiety to a fluorescence emission intensity of the emissive isosbestic point for the composition or between a fluorescence emission intensity of the second fluorescent moiety to a fluorescence emission intensity of the emissive isosbestic point for the composition.

22-36. -36. (canceled)

25. A method of making a composition comprising:

linking a first fluorescent moiety to a second fluorescent moiety, wherein the first fluorescent moiety or the second fluorescent moiety includes a semiconductor nanocrystal.

26. The method of claim 25, wherein after linking the first fluorescent moiety, when excited, is capable of transferring energy to the second fluorescent moiety.

27. The method of claim 25, wherein the second fluorescent moiety is capable of binding an analyte.

28. The method of claim 27, wherein an emission intensity of the second fluorescent moiety is altered when second fluorescent moiety binds the analyte.

29. The method of claim 25, wherein the semiconductor nanocrystal includes an outer layer including a compound linked to a surface of the nanocrystal and having a first hydrophobic region.

30. The method of claim 29, wherein linking includes contacting the semiconductor nanocrystal with an amphiphilic compound having a second hydrophobic region.

31. The method of claim 30, further comprising linking the second fluorescent moiety to the amphiphilic compound.

32. The method of claim 25, wherein linking includes coupling a surface of the nanocrystal and the second fluorescent moiety with a polyethylene glycol or a dendrimer.

33. The method of claim 31, wherein the amphiphilic compound is linked to the second fluorescent moiety.

34. The method of claim 25, wherein linking includes contacting the semiconductor nanocrystal with a compound including a coordinating group having an affinity for a surface of the semiconductor nanocrystal, and a fluorescent moiety.

35. The method of claim 25, wherein the semiconductor nanocrystal includes an outer layer including a compound having a first reactive functional group.

36. The method of claim 35, wherein linking includes contacting the semiconductor nanocrystal with a compound including a second reactive functional group capable of reacting with the first reactive functional group to form a bond, and a fluorescent moiety.

37. The method of claim 25, wherein the semiconductor nanocrystal includes a ZnSe or CdZnS core.