Assay cartridges and methods of using the same
Assay cartridges are described that have a detection chamber, preferably having integrated electrodes, and other fluidic components which may include sample chambers, waste chambers, conduits, vents, bubble traps, reagent chambers, dry reagent pill zones and the like. In certain embodiments, these cartridges are adapted to receive and analyze a sample collected on an applicator stick. Also described are kits including such cartridges and a cartridge reader configured to analyze an assay conducted using an assay cartridge.
1. A method of collecting a liquid in an assay cartridge, said method comprises the steps of:
introducing a first liquid portion containing bubbles into a collection chamber via a collection conduit until a liquid level reaches a first height in said collection chamber, wherein said collection conduit is connected proximate to a top of said collection chamber;
introducing a second liquid portion into the collection chamber via the collection conduit, wherein the first liquid portion and the second liquid portion are combined in the collection chamber;
transferring a third liquid portion from the collection chamber to the sensing chamber via a sensing conduit extending from proximate the top of the collection chamber to the first height, wherein the third liquid portion is a volume of the first liquid portion and the second liquid portion combined in the collection chamber that extends above the first height of the collection chamber;
detecting liquid from the third liquid portion in said sensing chamber; and
transferring a fourth liquid portion substantially free of bubbles from said collection chamber through an outlet conduit connected proximate to a bottom of said collection chamber;
wherein the first height is less than a second height from the top to the bottom of said collection chamber.
2. The method of claim 1 wherein said collection chamber further comprises a baffle positioned adjacent to said collection conduit, and said method further comprises contacting said first liquid portion and said second liquid portion with said baffle and a wall of said collection chamber to constrain bubbles within said first liquid portion and said second liquid portion.
3. The method of claim 1 , wherein the liquid from the third liquid portion is detected in said sensing chamber by an optical sensor.
4. The method of claim 3 , wherein the optical sensor is located on a cartridge reader.
5. The method of claim 3 , wherein the optical sensor is located on the cartridge.
6. The method of claim 3 , wherein the optical sensor is located beneath the sensing conduit.
7. The method of claim 1 , wherein the fourth liquid portion is transferred through said output conduit when said output conduit is exposed to a vacuum source and a sensing chamber vent is vented.
8. The method of claim 7 , wherein the sensing chamber vent is connected to a top of the sensing chamber.
9. The method of claim 1 , wherein the fourth liquid portion is transferred through said output conduit when said output conduit is vented and a sensing chamber vent is exposed to a positive pressure source.
10. The method of claim 9 , wherein the sensing chamber vent is connected to a top of the sensing chamber.
11. The method of claim 1 , wherein a ratio of dimensional measurements of a volume of the first liquid portion to the air head space volume in the collection chamber is 1:2 after the first liquid portion has reached the first height.
12. The method of claim 11 , wherein the volume of the first liquid portion is 125 μL and the air head space volume is 250 μL.
13. The method of claim 1 , wherein the sensing conduit connects to a top of the sensing chamber proximal to a wall of the sensing chamber.
14. The method of claim 1 , wherein the third liquid portion that is transferred through the sensing conduit into the sensing chamber is substantially free of bubbles.
15. The method of claim 1 , wherein the assay cartridge includes a waste chamber.
16. The method of claim 1 , wherein the sensing chamber further includes a baffle positioned adjacent to said sensing conduit, and said method further includes contacting the third liquid portion with said baffle and a wall of said sensing chamber.