Reusable detection surfaces and methods of using same

1. A method comprising:

introducing a sample including a plurality of magnetic particles and an analyte into a fluid chamber including a detection surface comprising an acoustic device having a vibrating membrane and a first capture agent linked to the detection surface, wherein the sample includes at least one magnetic particle, of the plurality of magnetic particles, functionalized with a second capture agent capable of binding the analyte bound to a third capture agent coupled to at least one non-analyte tag molecule;

binding the non-analyte tag molecule to the first capture agent and binding the second capture agent to the analyte;

monitoring, using the detection surface, a first signal output generated by interaction of the vibrating membrane and the plurality of magnetic particles; and

generating a flow transient over the detection surface for removing the non-analyte tag molecule from the first capture agent;

removing the non-analyte tag molecule from the first capture agent while the first capture agent remains linked to the detection surface so that the first capture agent is reusable.

2. The method of claim 1 wherein the first capture agent has a lower binding affinity for the non-analyte tag molecule than the second capture agent has for the analyte.

3. The method of claim 1 further comprising:

binding a second non-analyte tag molecule of the sample to the first capture agent;

monitoring, using the detection surface, a second signal output generated by interaction of the vibrating membrane and the plurality of magnetic particles; and

removing the second non-analyte tag molecule from the first capture agent while the first capture agent remains linked to the detection surface.

4. The method of claim 1 further comprising exposing the detection surface to a solution to remove the non-analyte tag molecule from the first capture agent.

5. The method of claim 3 further comprising exposing the detection surface to a solution to remove the non-analyte tag molecule from the first capture agent prior to binding the second non-analyte tag molecule of the sample to the first capture agent.

6. The method of claim 1 further comprising restricting flow of the chemical wash upstream of the detection surface while pumping flow of the chemical wash downstream of the detection surface and then removing the restriction after a first period of time to generate the flow transient.

7. The method of claim 3 further comprising generating a flow transient over the detection surface to remove the non-analyte tag molecule from the first capture agent prior to binding the second non-analyte tag molecule of the sample to the first capture agent.

8. The method of claim 7 further comprising restricting flow of the chemical wash upstream of the detection surface while pumping flow of the chemical wash downstream of the detection surface and then removing the restriction after a first period of time to generate the flow transient.

9. The method of claim 4 wherein the solution comprises one of a salt solution, a phosphate buffered saline, or phosphoric acid.

10. The method of claim 4 wherein the solution is acidic.

11. The method of claim 3 wherein the first signal output is suitable to detect a first concentration of the analyte and the second signal output is suitable to detect a second concentration of the analyte, wherein the second concentration is at least 50% less than the first concentration of the analyte.

12. The method of claim 1 wherein the first capture agent is an antibody or antigen binding fragment thereof.

13. The method of claim 1 wherein the affinity of the second capture agent for the analyte is greater than 2×10 9 M −1 .

14. The method of claim 1 wherein the affinity of the second capture agent for the analyte is greater than about 2 times the affinity of the first capture agent for the analyte.