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Enzyme electrode system
| Details |
Inventors: Pollmann, Klaus H.; Gerber, Martin T.;
Assignee: Boehringer Mannheim Corporation (Indianapolis, IN)
Primary Examiner: Wityshyn; Michael G.
Assistant Examiner: Beisner; William H.
Attorney, Agent or Firm: Young; D. Michael, Kenemore; Max J., Amick; Marilyn L.
A biosensor that includes working and counter electrodes of substantially the same size and made of the same electrically conducting material. A reagent is contained in a reagent well in the biosensor. The reagent includes a redox mediator, an enzyme, and a buffer, and covers substantially equal surface areas of portions of the working and counter electrodes. When a sample, containing the analyte to be measured, is added to the reagent well, a reaction occurs that oxidizes the analyte and reduces the redox mediator. After this reaction is complete, an electrical potential difference is applied between the electrodes. The amount of oxidized form of the redox mediator at the counter electrode and the applied potential difference must be sufficient to cause diffusion limited electrooxidation of the reduced form of the redox mediator at the surface of the working electrode. After a short time delay, current produced by the electrooxidation of the reduced form of the redox mediator is measured and the observed current is correlated to the amount of the analyte in the sample. In some cases, the analyte sought to be measured may be reduced and the redox mediator may be oxidized. In such cases, current produced by diffusion limited electroreduction of the oxidized form of the redox mediator is measured and correlated to the amount of analyte in the sample. |
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DETAILED DESCRIPTION The invention is a new biosensor (an electrochemical device) and method of its use.
The biosensor includes working and counter electrodes of substantially the same size, made of the same electrically conducting material, and affixed to a first electrical insulator.
Overlaying the electrodes is a second electrical insulator that includes a cutout portion that exposes substantially equal surface areas of the working and counter electrodes.
A reagent is added to the cutout portion.
The reagent substantially covers the exposed electrode surfaces in the cutout portion and includes a redox mediator, an enzyme and a buffer.
When a sample containing an analyte is added to the reagent, the analyte, enzyme, and the redox mediator participate in a reaction, wherein the redox mediator is either reduced (receives at least one electron) or is oxidized (donates at least one electron).
Usually, in this reaction, the analyte is oxidized and the redox mediator is reduced.
After this reaction (wherein analyte is oxidized and redox mediator is reduced) is complete, an electrical potential difference is applied between the electrodes.
The amount of oxidized form of the redox mediator at the counter electrode and the applied potential difference must be sufficient to cause diffusion limited electrooxidation of the reduced form of the redox mediator at the surface of the working electrode.
After a short time delay, current produced by the electrooxidation of the reduced form of the redox mediator is measured and the observed current is correlated to the amount of the analyte in the sample.
Importantly, only two electrodes of substantially the same size and made of the same electrically conducting material are required when the reagent includes a sufficient amount of the oxidized form of the redox mediator to insure that the current produced during electrooxidation is limited by the oxidation of the reduced form of the redox mediator at the working electrode surface.
For current produced during electrooxidation to be limited by the oxidation of the reduced form of the redox mediator at the working electrode surface, the amount of oxidized form of the redox mediator at the surface of the counter electrode must always exceed the amount of reduced form of the redox mediator at the surface to the working electrode
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