Method of detecting biosensor filling
The present invention is directed to methods of detecting filling of the capillary channel of a biosensor test strip. In one embodiment the biosensor test strip has three electrodes: a first reference electrode, a working electrode and a second reference electrode, which are arranged sequentially within the capillary channel of a biosensor test strip and perpendicular to the axis thereof. A test sample containing an analyte of interest is applied to the test strip. A first voltage (V 1 ) is applied between the first reference electrode and the working electrode, and a first current (i 1 ) is detected. If i 1 is detected, a second voltage (V 2 ) is applied between the working electrode and the second reference electrode. A second current (i 2 ) is detected, indicating that an applied sample has covered the first and second reference electrodes and the working electrodes. The measuring device then conducts the assay for the presence or amount of the analyte of interest in the test sample.
1 . A method of detecting application of liquid sample to a biosensor comprising
contacting the liquid sample with a biosensor comprising
an opening to a capillary channel containing a first reference electrode, a working electrode, and a second reference electrode comprised on a substrate,
electrically connecting the biosensor to a device for applying voltage to the biosensor;
applying a first voltage (V 1 ) to the working electrode relative to the first reference electrode and detecting a first current (i 1 );
applying a second voltage (V 2 ) to the working electrode relative to the second reference electrode and detecting a second current (i 2 ), wherein the presence of i 2 indicates sample has been applied to the biosensor;
thereby detecting application of the liquid sample to the biosensor.
2 . The method of claim 1 wherein the first reference electrode, working electrode, and second reference electrode lie perpendicular to the axis of the capillary channel.
3 . The method of claim 2 wherein the first reference electrode, working electrode, and second reference electrode are comprised on sequential axes lying perpendicular to the axis of the capillary channel.
4 . The method of claim 3 wherein the sequential axes are linear axes.
5 . The method of claim 3 wherein the first reference electrode is closest to the sample opening of the capillary channel and the second reference electrode is farthest from the sample opening of the capillary channel.
6 . The method of claim 1 wherein the biosensor further comprises a vent for passage of air from the capillary channel to the exterior of the biosensor.
7 . The method of claim 1 the biosensor further comprises at least three leads for independently connecting the first reference electrode, working electrode, and second reference electrode to at least three independent contacts of a metering device.
8 . The method of claim 1 wherein the electrodes are comprised of an electrically conducting ink.
9 . The method of claim 8 wherein the electrically conducting ink is comprised of a material selected from the group consisting of: silver, platinum, palladium, gold, carbon, and any combination thereof.
10 . The method of claim 1 wherein the biosensor further comprises reagents for detecting an analyte comprised within the capillary channel.
11 . The method of claim 10 wherein the reagents comprise an enzyme and a mediator.
12 . The method of claim 11 wherein the enzyme is deposited only on the working electrode and the mediator is deposited on all three electrodes.
13 . The method of claim 1 wherein if i 1 is detected, V 1 is discontinued before applying the second voltage (V 2 ).
14 . The method of claim 13 wherein if i 2 is detected, the device determines the concentration or amount of an analyte in the liquid sample.
15 . The method of claim 1 wherein if i 1 is not detected, an error is reported.
16 . The method of claim 1 wherein if i 1 is detected but i 2 is not detected, then an error is reported.
17 . The method of claim 10 wherein the biosensor comprises reagents for detecting an analyte selected from the group consisting of: glucose, cholesterol, and alcohol.
18 . The method of claim 1 wherein the sample is a biological sample.
19 . The method of claim 1 wherein the sample is blood or a blood product.
20 . The method of claim 1 wherein the biosensor comprises a polyester substrate.
21 . The method of claim 20 wherein the capillary is formed from a spacer and hydrophilic top cover comprised on the substrate.