Detection of target molecules in a sample by using a magnetic field

1. A method for detecting presence of target molecules in a sample, the method comprising:

a) contacting the sample and first binding molecules attached to magnetic particles, at a same time or at different times, with second binding molecules attached to a solid support, wherein the first binding molecules are capable of binding to the second binding molecules, and wherein the target molecules are capable of interfering with the first binding molecules binding to the second binding molecules such that a portion of the first binding molecules attached to magnetic particles are not bound to the second binding molecules; and applying a magnetic force to bring the magnetic particles into close proximity with the solid support; and

b) determining magnetic particles bound to the solid support by virtue of the binding of the first binding molecules attached to magnetic particles to the second binding molecules, wherein the determining of the bound magnetic particles comprises removing the portion of the first binding molecules attached to magnetic particles that are not bound to the second binding molecules, and allowing third binding molecules, which are capable of selectively binding to the first binding molecules, to bind to the first binding molecules that are bound to the second binding molecules, and detecting the binding of the third binding molecules to the first binding molecules.

2. The method of claim 1 , wherein the first binding molecules are capable of selectively binding to the target molecules in the sample and the second binding molecules, and wherein the contacting of the sample and the first binding molecules enables competition of the second binding molecules with the target molecules for said selective binding to the first binding molecule.

3. The method of claim 2 , wherein the second binding molecules are identical to the target, or are target homologues.

4. The method of claim 1 , wherein the second binding molecules are capable of selectively binding the target molecules in the sample and the first binding molecules, and wherein the contacting of the sample and the first binding molecules enables competition of the first binding molecules with the target molecules for said selective binding to the second binding molecules.

5. The method of claim 4 , wherein the first binding molecules are identical to the target molecules, or are target homologues.

6. The method of claim 1 , wherein the target molecules are selected from the group consisting of a small molecule, a drug, a protein, a peptide, an enzyme, a hormone and a nucleic acid.

7. The method of claim 1 , wherein the target molecules comprise an addictive drug, selected from the group consisting essentially of morphine, cocaine, tetrahydrocannabinol (THC), anabolics, or a drug of an amphetamine/methamphetamine group.

8. The method of claim 1 , wherein the magnetic force is applied in such a way so as to reduce or eliminate an impact of a difference in mobility between the target molecules and the first binding molecules attached to magnetic particles with regard to binding to the second binding molecules.

9. The method of claim 8 , wherein the magnetic force is applied using an electromagnet, an air-cored coil, or a permanent magnet.

10. The method of claim 1 , wherein the first binding molecules are respectively attached to said magnetic particles via spacer molecules, proteins or strong binding couples.

11. The method of claim 10 , wherein the spacer molecules comprise alkylene diamine or ethylene diamine.

12. The method of claim 1 , wherein the solid support is a surface of a sensor device.

13. The method of claim 12 , wherein the surface of the sensor device is a gold surface.

14. The method of claim 13 , wherein the gold surface is coated with a protein to which the second binding molecules are bound.

15. The method of claim 1 , wherein said sample consists of, or is derived from, urine, blood, sweat, ocular fluid, saliva, or hair.

16. The method of claim 1 , wherein the magnetic particles are selected from the group consisting essentially of magnetic, diamagnetic, paramagnetic, superparamagnetic, ferrimagnetic, and ferromagnetic particles.

17. The method of claim 1 , wherein each of the magnetic particles has a size from about 10 nm to about 10 μm.

18. The method of claim 1 , wherein each of the magnetic particles has a size from about 50 nm to about 1 μm.

19. The method of claim 1 , wherein each of the magnetic particles has a size from about 100 nm to about 500 nm.