Biological applications of quantum dots

• US 6,326,144 B1
• Filed: 09/24/1998
• Issued: 12/04/2001
• Est. Priority Date: 09/18/1998
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Mikulec, Frederick V., Bawendi, Moungi G., Sundar, Vikram C.
• Primary Examiner(s): Le, Long V.
• Assistant Examiner(s): PHAM, MINH QUAN K
• Application Number:
  US09/160,454
• Time in Patent Office: 1,167 Days
• Field of Search: 436/172, 436/546, 436/2, 435/6, 435/7.1, 250/307, 250/302, 250/459.1, 356/317, 252/301.7, 252/301.33, 252/301.36, 378/47, 422/82.08
• US Class Current: 435/6.11
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: C12Q 1/6804 Nucleic acid analysis using immunogens immunoassay G01N33/53
• CPC Class Codes: C12Q 1/6825 Nucleic acid detection involving sensors
• CPC Class Codes: C12Q 2527/125 Specific component of sample, medium or buffer
• CPC Class Codes: C12Q 2563/107 fluorescence
• CPC Class Codes: C12Q 2565/101 Interaction between at least two labels
• CPC Class Codes: C12Q 2565/607 being a sensor, e.g. electrode
• CPC Class Codes: G01N 33/532 Production of labelled immunochemicals
• CPC Class Codes: G01N 33/533 with fluorescent label
• CPC Class Codes: G01N 33/582 with fluorescent label
• CPC Class Codes: G01N 33/588 with semiconductor nanocrystal label, e.g. quantum dots
• CPC Class Codes: G06K 19/06046 Constructional details

Abstract

The present invention provides a composition comprising fluorescent semiconductor nanocrystals associated to a compound, wherein the nanocrystals have a characteristic spectral emission, wherein said spectral emission is tunable to a desired wavelength by controlling the size of the nanocrystal, and wherein said emission provides information about a biological state or event.

Claims

1. A composition comprising:

a compound; and

a semiconductor nanocrystal linked to the compound by a ligand of the formula H_zX((CH₂)_nCO₂H)_y and salts thereof, where X is S, N, P or O═

P;

n≧

6; and

z and y are selected to satisfy the valence requirements of X, the nanocrystal having a characteristic spectral emission, wherein said spectral emission is tunable to a desired wavelength by controlling the size of the nanocrystal, and wherein said emission provides information about a biological state or event.

2. The composition of claim 1, wherein the nanocrystal further comprises:

a layer overcoating the semiconductor nanocrystal, the layer being comprised of a material having a band gap greater than that of the semiconductor nanocrystal.

3. The composition of claim 1, wherein the said compound has an affinity for a biological target.

4. The composition of claim 3, wherein the affinity is a specific affinity.

5. The composition of claim 4, wherein the affinity of the compound to the biological target is due to a noncovalent, hydrophobic, hydrophilic, electrostatic, van der Waals, hydrogen bonding, or magnetic attraction.

6. The composition of claim 1, wherein the biological state for which information is provided is selected from the group consisting of:

quantitative and qualitative presence of a biological moiety;

structure, composition, and conformation of a biological moiety; and

localization of a biological moiety in an environment.

7. The composition of claim 1, wherein the biological event for which information is provided is selected from the group consisting of:

an interaction between biological moieties, an alteration in structure of a biological compound, and an alteration in a biological process.

8. The composition of claim 1, wherein the link between the compound and the nanocrystal is accomplished through an association selected from the group consisting of covalent, noncovalent, hydrophobic, hydrophilic, electrostatic, magnetic and coordination through a metal complex.

9. The composition of claim 1, wherein the ligand includes a first end linked to the nanocrystal and a second end coupled to the compound.

10. The composition of claim 1 or 2, wherein compound is a biological compound.

11. The composition of claim 10, wherein the biological compound is a protein, a peptide, a nucleic acid a carbohydrate, a cell, a lipid, a cellular organelle, or a signaling molecule.

12. The composition of claim 10, wherein the compound comprises a peptide.

13. The composition of claim 10, wherein the compound comprises a protein.

14. The composition of claim 13, wherein the protein comprises an antibody.

15. The composition of claim 14, wherein the antibody comprises a polyclonal or a monoclonal antibody.

16. The composition of claim 13, wherein the protein comprises avidin or streptavidin.

17. The composition of claim 10, wherein the biological compound comprises a nucleic acid.

18. The composition of claim 17, wherein the biological compound comprises an oligonucleotide.

19. The composition of claim 18, wherein the oligonucleotide is at least approximately 20-30 nucleotides long.

20. The composition of claim 17, wherein the biological compound is selected from the group consisting of:

a ribonucleotide, a deoxyribonucleotide, a dideoxyribonucleotide and derivatives thereof.

21. The composition of claim 17, wherein the biological compound is selected from the group consisting of:

a single stranded nucleic acid, a double stranded nucleic acid, a triple stranded nucleic acid cluster, a Holliday junction, a circular single-stranded DNA, a circular double-stranded DNA, and a DNA cube.

22. The composition of claim 1, wherein the compound comprises a small molecule.

23. The composition of claim 22, wherein the small molecule is biotin.

24. The composition of claim 23, wherein the small molecule is an enzyme inhibitor.

25. The composition of claim 1, wherein the compound is linked to the nanocrystal through a bridging biotin:

avidin complex.

26. The composition of claim 1, wherein the compound is linked to the nanocrystal through a bridging biotin:

streptavidin complex.

27. The composition of claim 1, wherein the nanocrystal is a member of a monodisperse particle population.

28. The composition of claim 1, wherein the nanocrystal comprises:

a semiconductor material having a selected band gap energy;

a layer overcoating the semiconductor material, the overcoating layer comprised of a material having a band gap energy greater than that of the semiconductor material; and

an outer layer, the layer comprising the ligand, the ligand having at least one linking group for attachment of the compound to the overcoating layer and at least one hydrophilic group spaced apart from the linking group by a hydrophobic region sufficient to prevent electron charge transfer across the hydrophobic region.

29. The composition of claim 28, wherein the linking group comprises a moiety selected from the group consisting of an amine, a thiol, a phosphine, a phosphine oxide, and an amine oxide.

30. The composition of claim 28, wherein the hydrophilic group is selected from the group consisting of carboxylic acid, carboxylate, sulfonate, hydroxide, alkoxide, ammonium salt, and phosphate.

31. The composition of claim 28, wherein the nanocrystal exhibits photoluminescence having a quantum yield of greater than 10% in water.

32. The composition of claim 28, wherein the nanocrystal exhibits photoluminescence having a quantum yield in the range of about 10-30% in water.

33. The composition of claim 1 or 28, wherein the nanocrystal is a ZnS overcoated CdSe nanocrystal.

34. The composition of claim 1, wherein a plurality of nanocrystals exhibit less than a 10% rms deviation in diameter.

35. The composition of claim 1, wherein a plurality of nanocrystals exhibit an emission spectrum having a linewidth of less than about 40 nm at full width at half maximum (FWHM).

36. The composition of claim 1, wherein a plurality of nanocrystals exhibit an emission spectrum having a linewidth of a spectral range that is less than about 25 nm at full width at half maximum (FWHM).

37. The composition of claim 1, wherein the nanocrystal has a spectral range that is less than about 12-15 nm at full width half maximum (FWHM).

38. The composition of claim 1, wherein the nanocrystal is a Group II-VI, III-V or IV semiconductor.

39. The composition of claim 1, wherein the nanocrystal has a narrow spectral emission range selected from the spectrum in the range of about 300 nm to about 1500 nm.

40. The composition of claim 1, wherein the nanocrystal has a core particle size selected from the range of about 12 Å

to about 150 Å

.

41. The composition of claim 1, wherein the compound is linked to the nanocrystal by means of covalent attachment.

42. The composition of claim 1, wherein the compound is linked to the nanocrystal directly through a thiol or an amine group coordinated to the semiconductor nanocrystal.

43. The composition of claim 1, wherein the compound is linked to the nanocrystal by means of covalent coupling of a carboxylic acid moiety with an amine group of the compound.

44. A composition comprising:

a semiconductor nanocrystal having a selected band gap energy;

an overcoating layer disposed on the semiconductor nanocrystal, the overcoating layer comprised of a material having a band gap energy greater than that of the semiconductor nanocrystal;

an outer layer disposed about the overcoating layer, the outer layer comprising a plurality of ligands, each having at least one linking group for attachment of the ligand to the overcoating layer and at least one hydrophilic group spaced apart from the linking group by a hydrophobic region sufficient to prevent electron charge transfer across the hydrophobic region; and

a compound linked to the overcoating layer, the nanocrystal exhibiting photoluminescence having a quantum yield of greater than 10% in water.

45. The composition of claim 44, wherein the compound is linked to the overcoating layer via a ligand of the outer layer.

46. The composition of claim 45, wherein the compound is linked to the hydrophilic group of the ligand.

47. The composition of claim 44, wherein the ligands of the outer layer solubilize the composition in water.

48. The composition of claim 44, wherein ligands of the outer layer comprise a compound of the formula, H_zX((CH₂)_nCO₂H)_y and salts thereof, where X is S, N, P or O═

P;

n≧

6; and

z and y are selected to satisfy the valence requirements of X.

49. The composition of claim 44, wherein ligands of the outer layer comprise a compound of the formula

where Y is a hydrophilic moiety; Z is a hydrophobic region having a backbone of at least six atoms; and

X and X′

are the same or different and are selected from the group consisting of S, N, P and O═

P.

50. The composition of claim 44, wherein ligands of the outer layer comprise a compound of the formula

where Y is a hydrophilic moiety;

Z is a hydrophobic region having a backbone of at least six atoms; and

X, X′

, and X″

, each are the same or different and are selected from the group consisting of S, N, P and O═

P.

51. The composition of claim 49 or 50, wherein the compound and the nanocrystal are disposed through an association selected from the group consisting of covalent, noncovalent, hydrophobic, hydrophilic, electrostatic, magnetic and coordination through a metal complex.

52. The composition of claim 49 or 50, wherein the ligand includes a first end linked to the nanocrystal and a second end coupled to the compound.

53. The composition of claim 49 or 50, wherein compound is a biological compound.

54. The composition of claim 53, wherein the biological compound is a protein, a peptide, a nucleic acid, a carbohydrate, a cell, a lipid, a cellular organelle, or a signaling molecule.

55. The composition of claim 54, wherein the biological compound comprises a protein.

56. The composition of claim 55, wherein the protein comprises an antibody.

57. The composition of claim 55, wherein the protein comprises avidin or streptavidin.

58. The composition of claim 54, wherein the biological compound comprises a nucleic acid.

59. The composition of claim 58, wherein the biological compound is selected from the group consisting of:

a ribonucleotide, a deoxyribonucleotide, a dideoxyribonucleotide and derivatives thereof.

60. The composition of claim 49 or 50, wherein the compound is biotin.

61. The composition of claim 49 or 50, wherein the compound is linked to the nanocrystal through a bridging biotin:

avidin complex.

62. The composition of claim 49 or 50, wherein the compound is linked to the nanocrystal through a bridging biotin:

streptavidin complex.

63. The composition of claim 49 or 50, wherein the nanocrystal is a Group II-VI, III-V or IV semiconductor.

64. The composition of claim 49 or 50, wherein the nanocrystal is a ZnS-overcoated CdSe nanocrystal.

65. The composition of claim 49 or 50, wherein Y is a carboxylate, a sulfonate, a phosphate, a polyethylene glycol or an ammonium salt.

66. The composition of claim 49 or 55, wherein Z is an alkyl group or alkenyl group, optionally including nitrogen atoms and optionally further modified to provide attractive interactions with neighboring ligands.

67. A water-soluble composition comprising:

a water-soluble semiconductor nanocrystal having a selected band gap energy; and

a compound linked to the semiconductor nanocrystal, wherein the water-soluble semiconductor nanocrystal exhibits photoluminescence having a quantum yield of greater than 10% in water.

68. The composition of claim 67, wherein the water-soluble semiconductor nanocrystal further includes a ligand of the formula, H_zX((CH₂)_nCO₂H)_y and salts thereof, linked to the water-soluble semiconductor nanocrystal, wherein X is S, N, P or O═

P;

n≧

6; and

z and y are selected to satisfy the valence requirements of X.

69. A water-soluble composition comprising:

a water-soluble semiconductor nanocrystal having a selected band gap energy; and

a compound linked to the semiconductor nanocrystal, wherein the water-soluble semiconductor nanocrystal exhibits photoluminescence having a quantum yield between about 10-30% in water.

70. A composition comprising:

a semiconductor nanocrystal having a selected band gap energy, wherein the semiconductor nanocrystal includes a ligand of the formula, H_zX((CH₂)_nCO₂H)_y or a salt thereof, where X is S, N, P or O═

P;

n≧

6; and

z and y are selected to satisfy the valence requirements of X; and

a compound linked to the semiconductor nanocrystal.

71. A composition comprising:

a semiconductor nanocrystal having a selected band gap energy, wherein the semiconductor nanocrystal includes a ligand of the formula

where Y is a hydrophilic moiety;

Z is a hydrophobic region having a backbone of at least six atoms; and

X and X′

are the same or different and are selected from the group consisting of S, N, P and O═

P.

72. A composition comprising:

a semiconductor nanocrystal having a selected band gap energy, wherein the semiconductor nanocrystal includes a ligand of the formula

where Y is a hydrophilic moiety;

Z is a hydrophobic region having a backbone of at least six atoms; and

X, X′

, and X″

, each are the same or different and are selected from the group consisting of S, N, P and O═

P.