Apparatus and methods for analyte measurement and immunoassay
The present invention relates to methods for measuring an amount of an analyte using an electrochemical assay in a conduit comprising a sensor, wherein said sensor comprises an electrode having a surface layer of immobilized antibody that binds said analyte, and a counter/reference electrode disposed within said conduit. A solution comprising a substrate for said enzyme and at least one air segment contacts the sensor to remove unbound analyte and labeled antibody from a region of the sensor. The disclosed invention is adaptable to the point-of-care clinical diagnostic field, including use in accident sites, emergency rooms, surgery, nursing homes, intensive care units, and non-medical environments.
1. A method of measuring an amount of an analyte using an electrochemical assay in a conduit comprising a sensor, wherein said sensor comprises an electrode having a surface layer of immobilized antibody that binds said analyte, and a counter/reference electrode disposed within said conduit, said method comprising:
contacting said sensor with a liquid sample containing said analyte;
contacting said sensor with an enzyme-labeled antibody capable of binding said analyte, whereby a complex of immobilized antibody, analyte and labeled antibody is formed;
contacting said sensor with a solution comprising a substrate for said enzyme and at least one air segment to remove unbound analyte and labeled antibody from a region of the sensor;
removing substantially all said solution from said sensor while retaining a portion of said solution over said electrode, said counter/reference electrode, and a contiguous portion of a wall of the conduit connecting said electrodes; and
detecting a product of a reaction between said enzyme-labeled antibody and said substrate using said sensor, whereby the amount of said analyte in the liquid sample is measured.
2. The method of claim 1 , wherein the sample comprises the enzyme-labeled antibody dissolved therein.
3. The method of claim 1 , wherein the enzyme-labeled antibody is subsequently delivered in a liquid to the sensor that is not the sample, prior to delivery of said solution.
4. The method of claim 1 , wherein the retained portion of said solution comprises a predetermined volume.
5. The method of claim 1 , wherein at least a portion of the wall of the conduit is treated to reduce non-specific binding of the enzyme-labeled antibody.
6. The method of claim 1 , wherein the at least one air segment is formed by evacuation of the conduit.
7. The method of claim 1 , further comprising:
displacing the liquid sample from the sensor into a waste region prior to the contacting the sensor with the solution; and
providing the solution in another conduit,
wherein the contacting the sensor with the solution comprises displacing the solution from the another conduit into contact with the sensor.
8. The method of claim 7 , wherein the displacing the liquid sample into the waste region closes a first vent.
9. The method of claim 8 , wherein the at least one air segment is formed by forcing air through a second vent into the conduit.
10. The method of claim 9 , wherein:
the displacing the solution further comprises actuating a pump to create a lower pressure in the conduit; and
the actuating the pump occurs subsequent to the closing the first vent.
11. The method of claim 10 , wherein:
the second vent comprises a membrane that vibrates as the air is forced through the second vent providing an intermittent air stream; and
the intermittent air stream interrupts displacing the solution from the another conduit into contact with the sensor, and causes the forming the at least one air segment.