Microfluidic system for analyzing nucleic acids

1. A method of analyzing a nucleic acid target in a nucleic acid mixture of the target and non-target nucleic acids, the method comprising:

attracting the nucleic acid mixture in fluid to an electrode included in electronics formed on a substrate;

retaining the target selectively by binding the target to a receptor disposed near the electrode;

locally heating a portion of the fluid near the receptor to adjust a stringency under which the target binds to the receptor;

enriching the mixture for the target by removing unretained nucleic acids; and

amplifying the target from the enriched mixture.

2. The method of claim 1 , wherein enriching includes moving the unretained nucleic acids at least partially by mechanically driven flow.

3. The method of claim 2 , wherein moving is conducted under a binding stringency that is determined by at least one of heating and applying an electric field to the receptor.

4. The method of claim 1 , wherein attracting and retaining are conducted in a first compartment, amplifying being conducted in a distinct second compartment.

5. The method of claim 4 , further comprising moving the target from the first compartment to the second compartment after the step of enriching and before the step of amplifying.

6. The method of claim 1 , further comprising detecting the amplified target.

7. The method of claim 1 , the receptor being a nucleic acid that is at least substantially complementary to the target, the nucleic acid being connected to the electrode.

8. The method of claim 1 , amplifying being conducted with nucleic acid primers that are each distinct from the receptor.

9. The method of claim 1 , wherein the receptor is a first receptor, the method further comprising contacting a second receptor with the amplified target to assay the amplified target, the second receptor being configured to selectively bind the target.

10. The method of claim 9 , each of retaining and contacting being performed with a binding stringency, the stringency of contacting being greater than the stringency of retaining.

11. The method of claim 9 , the first and second receptors being identical.

12. The method of claim 11 , enriching and contacting being conducted In a shared compartment.

13. The method of claim 9 , amplifying and contacting being conducted in different compartments.

14. The method of claim 9 , the first and second receptors being distinct structurally and separated spatially.

15. The method of claim 1 , further comprising releasing the retained target before the step of amplifying.

16. A microfluidic device for analyzing a nucleic acid target in a nucleic acid mixture of the target and non-target nucleic acids, comprising:

a substrate portion at least partially defining fluidically connected first and second chambers, the substrate portion including a substrate and electronics formed on the substrate, the electronics including a first electrode operable to form an electric field in the first chamber and a second electrode operable to form an electric field in the second chamber, the electronics also including a plurality of heating devices operable to adjust binding stringency locally in at least one of the first and second chambers; and

first and second receptors for specifically binding the target, the first and second receptors being connected to the first and second electrodes, respectively.

17. The device of claim 16 , the first and second receptors being distinct.

18. The device of claim 16 , at least one of the heating devices being operable to reverse binding of the first receptor to the target.

19. The device of claim 16 , further comprising a fluid-handling portion connected to the substrate portion and configured to move fluid to and receive fluid from the first chamber.

20. The device of claim 19 , the fluid-handling portion being configured to move fluid at least partially by mechanically driven flow.

21. The device of claim 16 , at least one of the first and second electrodes being plural electrodes.