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Publication Number
US-8758582-B2
Publication Date
2014-06-24
Expiration Date
Abstract
An electrochemical test strip is formed from a first insulating substrate layer, a second substrate layer, and an intervening insulating spacer layer. An opening in the insulating spacer layer defines a test cell which is in contact with the inner surface of the first substrate on one side and the inner surface of the second substrate on the other side. The size of the test cell is determined by the area of substrate exposed and the thickness of the spacer layer. Working and counter electrodes appropriate for the analyte to be detected are disposed on the first insulating substrate in a location within the test cell. The working and counter electrodes are associated with conductive leads that allow The second substrate is conductive at least in a region facing the working and counter electrodes. No functional connection of this conductive surface of the second substrate to the meter is required. When a potential difference is applied between the working and counter electrodes, because of the presence of the conductive surface on the second substrate, the relevant diffusion length is not dependent on the distance between working and counter electrodes, but is instead dependent on the distance between the first and second substrates (i.e., on the thickness of the spacer layer). This means that shorter measurement times can be achieved without having to reduce the spacing of the working and counter electrodes.
Core Innovation
The electrochemical test strip for detecting an analyte includes a first insulating substrate layer, a second substrate layer, and an intervening insulating spacer layer. An opening in the insulating spacer layer defines a test cell that is in contact with an inner surface of the first substrate on one side and an inner surface of the second substrate on the other side, and the size of the test cell is determined by the area of the first and second substrates exposed and the thickness of the spacer layer.
Working and counter electrodes appropriate for the analyte are disposed on the first insulating substrate within the test cell and are associated with conductive leads to connect to a meter for determination of analyte. A region of the second substrate facing the working and counter electrodes is conductive and has no connector for connection with a meter for determination of analyte. A redox mediator is disposed in the test cell.
A potential is applied between the working and counter electrodes, but not to the conductive region of the second substrate, thereby reducing an oxidized form of the redox mediator at the counter electrode and oxidizing a reduced form of the redox mediator at the working electrode, which generates a current indicative of analyte in the sample. The overall transfer of electrons from the counter electrode to the working electrode is accomplished by diffusion of reduced mediator from the counter electrode to the conductive region of the second substrate and then diffusion of reduced mediator from the conductive region of the second substrate to the working electrode.
Claims Coverage
The provided material identifies one independent claim (clm-00001), describing an electrochemical analyte-detection method using a two-insulating-substrate test cell separated by an insulating spacer, with a conductive region on the second substrate that is not electrically connected to the meter. The claim includes four inventive features related to the test-cell geometry, the electrode and conductive-region electrical separation, potential application, and electron transfer via diffusion through the conductive region.
Diffusion-defined test cell with spacer-determined geometry
A test cell is defined by an opening in an intervening insulating spacer layer between a first insulating substrate layer and a second substrate layer, where the test cell size is determined by the area of exposed first and second substrates and the thickness of the spacer layer.
Conductive second-substrate region not connected to meter
A region of the second substrate facing the working and counter electrodes is conductive and has no connector for connection with a meter for determination of analyte.
Potential applied between working and counter electrodes only
Applying a potential between the working and counter electrodes, but not to the conductive region of the second substrate, thereby reducing an oxidized form of the redox mediator at the counter electrode and oxidizing a reduced form of the redox mediator at the working electrode to generate a current indicative of analyte.
Electron transfer accomplished by diffusion via conductive region
Overall transfer of electrons from the counter electrode to the working electrode is accomplished by diffusion of reduced mediator from the counter electrode to the conductive region of the second substrate and then diffusion of reduced mediator from the conductive region of the second substrate to the working electrode, followed by measuring the current to obtain a determination of analyte.
Across the independent claim, the inventive approach is to use a conductive region on the second substrate without meter connection to provide a diffusion-mediated electron-transfer pathway between counter and working electrodes, with the test-cell geometry and spacer thickness defining the diffusion distance while current is measured for analyte determination.
Stated Advantages
Reducing measurement time by making the key diffusion length depend on substrate spacing (spacer thickness) rather than electrode separation.
Enabling smaller sample volumes and improving concentration accuracy.
Documented Applications
Electrochemical detection of an analyte in a sample using a redox mediator and working/counter electrodes disposed within a test cell of an electrochemical test strip, including glucose detection described in the document as an example analyte.
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