Digital protein sensing chip and methods for detection of low concentrations of molecules

1. A system for determining whether a peptide is phosphorylated or not, the system comprising:

a first channel configured to receive a sample that includes cells, wherein the first channel includes a first antibody for capturing the cells, and the first channel is further configured to receive a lysis buffer for lysing the captured cells to generate a lysate having a target protein;

a second channel fluidly coupled to the first channel and configured to receive the lysate, wherein the second channel is functionalized with a second antibody for binding the target protein in the lysate, and the second channel is further configured to receive an eluting solution to generate an elution buffer including the target protein;

a third channel fluidly coupled to the second channel and configured to receive the elution buffer, wherein the third channel is further configured to fragment the target protein to generate a solution including one or more peptides; and

a sensing device fluidly coupled to the third channel and configured to receive the one or more peptides, the sensing device comprising (a) a first tunneling electrode, (b) an insulating layer covering a substantial portion of the first tunneling electrode, (c) a second tunneling electrode in contact with the insulating layer, wherein the insulating layer is sandwiched between the first and second tunneling electrodes, and (d) a nanopore through the first and second tunneling electrodes, wherein the nanopore is configured to produce an electrical signal indicative of the phosphorylating status of the one or more peptides when they pass through the nanopore.

2. The system of claim 1 , further comprising a fourth channel fluidly coupled to the third channel and configured to receive the solution including the one or more peptides, the fourth channel is functionalized with a third antibody for selectively capturing a subpopulation of the one or more peptides, the fourth channel including an outlet for the subpopulation.

3. The system of claim 2 , further comprising a fifth channel fluidly coupled to the third channel or the fourth channel, the fifth channel configured to receive the solution including the one or more peptides or the subpopulation, the fifth channel further configured to modify the one or more peptides or the subpopulation by attaching a charged polymer to each of the one or more peptides.

4. The system of claim 3 , wherein the fifth channel includes a buffer exchange column.

5. The system of claim 1 , wherein the third channel includes a plurality of trypsinized beads.

6. The system of claim 1 , wherein the sensing device further comprises a first reservoir in contact with the first tunneling electrode, and a second reservoir in contact with the second tunneling electrode, wherein the first and second reservoirs are in fluid communication through the nanopore.

7. The system of claim 6 , wherein the sensing device further comprises a first reference electrode in the first reservoir.

8. The system of claim 7 , wherein the sensing device further comprises a second reference electrode in the second reservoir.

9. The system of claim 1 , wherein the nanopore is about 2 nm to 10 nm in diameter.

10. The system of claim 1 , wherein the insulating layer is about 1 nm to 4 nm in thickness.

11. The system of claim 1 , further comprising a current monitor configured to generate an electrical signal when a molecule passes through the nanopore.

12. The system of claim 1 , further comprising a bias voltage source configured to establish a voltage bias between the first tunneling electrode and the second tunneling electrode.

13. The system of claim 1 , wherein the protein is JAK2 kinase.

14. The system of claim 1 , wherein the sample is whole blood.

15. The system of claim 1 , wherein the first and second tunneling electrodes are functionalized by a reader molecule.