Magnetic sensor based quantitative binding kinetics analysis

1. A method of quantitatively determining a binding kinetic parameter of a molecular binding interaction, the method comprising:

producing a magnetic sensor device comprising a magnetic sensor comprising a spin valve sensor or a magnetic tunnel junction sensor in contact with an assay mixture comprising a magnetically labeled molecule suspended in a solution to produce a detectable molecular binding interaction, wherein the magnetic sensor comprises a molecule that specifically binds to the magnetically labeled molecule;

obtaining a real-time signal from the magnetic sensor without washing non-specific magnetic labels from the magnetic sensor; and

quantitatively determining with a quantitative analysis module of the magnetic sensor device a binding kinetic parameter of the molecular binding interaction from the real-time signal, wherein the quantitatively determining comprises processing the real-time signal with a two-compartment fitting algorithm.

2. The method according to claim 1 , wherein the binding kinetic parameter is an association rate constant (k a ).

3. The method according to claim 1 , wherein the binding kinetic parameter is a dissociation rate constant (k d ).

4. The method according to claim 1 , wherein the binding kinetic parameter is a diffusion-limited rate constant (k M ).

5. The method according to claim 1 , wherein the producing comprises applying the magnetically labeled molecule to the magnetic sensor.

6. The method according to claim 1 , wherein the magnetic sensor comprises a capture probe that specifically binds to a molecule that specifically binds to the magnetically labeled molecule, and the producing comprises sequentially applying the molecule that specifically binds to the magnetically labeled molecule and the magnetically labeled molecule to the magnetic sensor.

7. The method according to claim 1 , wherein the magnetic sensor comprises a capture probe that specifically binds to a molecule that specifically binds to the magnetically labeled molecule, and the producing comprises producing a reaction mixture comprising the molecule that specifically binds to the magnetically labeled molecule and then applying the reaction mixture to the magnetic sensor.

8. The method according to claim 1 , wherein the molecular binding interaction is a binding interaction selected from the group consisting of a nucleic acid hybridization interaction, a protein-protein interaction, a receptor-ligand interaction, an enzyme-substrate interaction, and a protein-nucleic acid interaction.

9. The method according to claim 1 , wherein the two-compartment fitting algorithm includes a bulk compartment and a surface compartment.

10. A method of quantitatively determining a binding kinetic parameter of two or more distinct molecular binding interactions, wherein each distinct molecular binding interaction includes a different magnetically labeled molecule, the method comprising:

producing a magnetic sensor device comprising two or more distinct magnetic sensors each comprising a spin valve sensor or a magnetic tunnel junction sensor each in contact with an assay mixture comprising a magnetically labeled molecule suspended in a solution to produce two or more distinct molecular binding interactions, wherein each magnetic sensor comprises a molecule that specifically binds to the magnetically labeled molecule;

obtaining a real-time signal from each magnetic sensor without washing non-specific magnetic labels from the magnetic sensors; and

quantitatively determining with a quantitative analysis module of the magnetic sensor device a binding kinetic parameter for each of the two or more distinct molecular binding interactions from the real-time signal, wherein the quantitatively determining comprises processing the real-time signal with a two-compartment fitting algorithm.

11. The method according to claim 10 , wherein the binding kinetic parameter is an association rate constant (k a ).

12. The method according to claim 10 , wherein the binding kinetic parameter is a dissociation rate constant (k d ).

13. The method according to claim 10 , wherein the binding kinetic parameter is a diffusion-limited rate constant (k M ).

14. The method according to claim 10 , wherein the binding interactions are binding interactions selected from the group consisting of nucleic acid hybridization interactions, protein-protein interactions, receptor-ligand interactions, enzyme-substrate interactions, and protein-nucleic acid interactions.

15. The method according to claim 1 , wherein the magnetic sensor comprises a passivation layer having a thickness of 50 nm or less.

16. The method according to claim 1 , wherein the magnetic nanoparticle comprises a surfactant.

17. The method according to claim 9 , wherein a change in concentration of the magnetically labeled molecule in the surface compartment is described by the equation:

dC S /dt=k M ( C 0 −C S )− k a C S ( B max −B )+ k d B

wherein k M is a diffusion-limited rate constant, C 0 is a concentration of the magnetically labelled molecule in the bulk compartment, C S is a concentration of the magnetically labelled molecule in the surface compartment, k a is an association rate constant, B max is an initial available receptor concentration, B is a concentration of conjugate bound to the magnetic sensor, and k d is a dissociation rate constant.

18. The method according to claim 9 , wherein a change in concentration of the molecular binding interaction is described by the equation:

dB/dt=k a C S ( B max −B )− k d B

wherein k a is an association rate constant, C S is a concentration of the magnetically labelled molecule in the surface compartment, B max is an initial available receptor concentration, B is a concentration of conjugate bound to the magnetic sensor, and k d is a dissociation rate constant.