Magnetic nanoparticles, magnetic detector arrays, and methods for their use in detecting biological molecules
View Patent ↗Magnetic nanoparticles and methods for their use in detecting biological molecules are disclosed. The magnetic nanoparticles can be attached to nucleic acid molecules, which are then captured by a complementary sequence attached to a detector, such as a spin valve detector or a magnetic tunnel junction detector. The detection of the bound magnetic nanoparticle can be achieved with high specificity and sensitivity.
1. A method of detecting a complex, the method comprising:
providing a first molecule bonded to at least one magnetizable nanoparticle;
providing a second molecule bonded to a substrate;
contacting the first molecule to the second molecule under conditions suitable for selective binding of the first molecule to the second molecule to form a complex; and
detecting the complex, wherein said detecting comprises applying a DC bias field and then an AC tickling field sufficient to cause a detectable signal.
2. The method of claim 1 , wherein the first molecule comprises a first nucleic acid molecule and the second molecule comprises a second nucleic acid molecule.
3. The method of claim 1 , wherein the first molecule is DNA or RNA.
4. The method of claim 1 , wherein the second molecule is DNA or RNA.
5. The method of claim 1 , wherein the first molecule comprises a first protein molecule and the second molecule comprises a second protein molecule.
6. The method of claim 1 , wherein the first molecule comprises a first peptide molecule and the second molecule comprises a second peptide molecule.
7. The method of claim 1 , wherein the first molecule comprises an antigen molecule and the second molecule comprises an antibody molecule.
8. The method of claim 1 , wherein the first molecule comprises an antibody molecule and the second molecule comprises an antigen molecule.
9. The method of claim 1 , wherein the first molecule is covalently bonded to at least one magnetizable nanoparticle by a gold-thiol linkage.
10. The method of claim 1 , wherein the nanoparticle is nonmagnetic in the absence of a magnetic field and is magnetic in the presence of a magnetic field.
11. The method of claim 1 , wherein the nanoparticle is a paramagnetic particle, a superparamagnetic particle, or a synthetic ferrimagnetic particle.
12. The method of claim 1 , wherein the nanoparticle comprises a noble metal surface layer.
13. The method of claim 1 , wherein the nanoparticle comprises a gold surface layer.
14. The method of claim 1 , wherein the nanoparticle has a mean diameter of about 5 nm to about 250 nm.
15. The method of claim 1 , wherein the nanoparticle has a mean diameter of about 5 nm to about 20 nm.
16. The method of claim 1 , wherein the substrate comprises a high sensitivity spin valve or a magnetic tunnel junction detector array.
17. The method of claim 1 , wherein the detecting step comprises applying an external magnetic field gradient.
18. The method of claim 1 , wherein the detecting step comprises applying an external magnetic field gradient and detecting a net magnetic moment.
19. The method of claim 1 , wherein the AC tickling field is applied orthogonally to the DC bias field.
20. The method of claim 1 , wherein the DC bias field is substantially parallel to the substrate.
21. The method of claim 1 , wherein the substrate comprises a passivation layer having a thickness of 10 nm or less.